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Flaxseed protein: extraction, functionalities and applications

Abstract

Flaxseed (Linum usitatissimum L.), one kind of common oilseeds, has many biologically active compounds including α-linolenic acid (ALA), lignan and dietary fiber. At present, the research of flaxseed is focused on biological and clinical studies of its compounds. However, the studies of flaxseed protein obtained generally from flaxseed cake, are relatively limited. As many other kinds of plant proteins, flaxseed protein presents many excellent functionalities which can be used for food applications. Many evidence have showed that flaxseed protein hydrolysates can provide health benefits to our body, such as anti-bacterial activity, antioxidant capacity and angiotensin-converting enzyme inhibition ability. Therefore, in order to make better use of flaxseed protein in foods, the extraction, functionalities and applications of flaxseed protein were reviewed in this paper. In addition, the preparation of flaxseed protein hydrolysates was discussed.

Keywords:
flaxseed protein; extraction; functionalities; hydrolysis; application

1 Introduction

Flaxseed, one kind of oilseeds, is worldwide grown in more than 50 countries. The global production output of flaxseed in 2018 is reached to 3.183 million tons (Food and Agriculture Organization, 2020Food and Agriculture Organization – FAO. (2020). Retrieved from http://www.fao.org/faostat/zh/#data/QC
http://www.fao.org/faostat/zh/#data/QC...
). Canada and China are the major producers of flaxseed, which account for around 33% of the total world output (Bekhit et al., 2018Bekhit, A. E. A., Shavandi, A., Jodjaja, T., Birch, J., Teh, S., Ahmed, I. A. M., Al-Juhaimi, F. Y., Saeedi, P., & Bekhit, A. A. (2018). Flaxseed: composition, deoxification, utilization, and opportunities. Biocatalysis and Agricultural Biotechnology, 13, 129-152. http://dx.doi.org/10.1016/j.bcab.2017.11.017.
http://dx.doi.org/10.1016/j.bcab.2017.11...
; Tang et al., 2021Tang, Z. X., Ying, R. F., Lv, B. F., Yang, L. H., Xu, Z., Yan, L. Q., Bu, J. Z., & Wei, Y. S. (2021). Flaxseed oil: extraction, health benefits and products. Quality Assurance and Safety of Crops & Foods, 13(1), 1-19. http://dx.doi.org/10.15586/qas.v13i1.783.
http://dx.doi.org/10.15586/qas.v13i1.783...
). Due to the high contents of ALA in flaxseed oil, lignans, dietary fibers and flaxseed proteins, the scientists have been showing the great enthusiasm for flaxseed studies (Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Wu et al., 2019Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017.
http://dx.doi.org/10.1016/j.tifs.2019.08...
; Yang, et al., 2021Yang, J., Wen, C., Duan, Y., Deng, Q., Peng, D., Zhang, H., & Ma, H. (2021). The composition, extraction, analysis, bioactivities, bioavailability and application in food system of flaxseed (Linum usitatissimum L.) oil: a review. Trends in Food Science & Technology, 118, 252-260. http://dx.doi.org/10.1016/j.tifs.2021.09.025.
http://dx.doi.org/10.1016/j.tifs.2021.09...
; Zou et al., 2017Zou, X., Chen, X., Hu, J., Wang, Y., Gong, D., Zhu, X., & Deng, Z. (2017). Comparisons of proximate compositions, fatty acids profile and micronutrients between fiber and oil flaxseeds (Linum usitatissimum L.). Journal of Food Composition and Analysis, 62, 168-176. http://dx.doi.org/10.1016/j.jfca.2017.06.001.
http://dx.doi.org/10.1016/j.jfca.2017.06...
). At present, many flaxseed-based products, such as whole flaxseeds, ground/milled flaxseeds, flaxseed oil, and lignan extracts, have been available (Shim et al., 2015Shim, Y. Y., Gui, B., Wang, Y., & Reaney, M. J. T. (2015). Flaxseed (Linum usitatissimum L.) oil processing and selected products. Trends in Food Science & Technology, 43(2), 162-177. http://dx.doi.org/10.1016/j.tifs.2015.03.001.
http://dx.doi.org/10.1016/j.tifs.2015.03...
). Particularly, the applications of flaxseed oil in many food systems, have been carried out (Lim et al., 2010Lim, C. W., Norziah, M. H., & Lu, H. F. S. (2010). Effect of flaxseed oil towards physico-chemical and sensory characteristic of reduced fat ice creams and its stability in ice creams upon storage. International Food Research Journal, 17, 393-403.; Tang & Bian, 2018aTang, Z. X., & Bian, J. Z. (2018a). Flaxseed nutritional food for lowing blood lipid and a preparation method thereof. CN 201811366312:A., bTang, Z. X., & Bian, J. Z. (2018b). Flaxseed nutritional food for strengthening brain and a production method thereof. CN 201811367137: A., cTang, Z. X., & Bian, J. Z. (2018c). Flaxseed protein beverage and a preparation method thereof. CN 201811252507: A., dTang, Z. X., & Bian, J. Z. (2018d). Nourishment enriched in proteins and flaxseed oil and a preparation method thereof. CN 201811252511.7., eTang, Z. X., & Bian, J. Z. (2018e). Pregnant woman food containing alpha-linolenic acid and a preparation method thereof. CN 201811367386:A.; Tang, 2019aTang, Z. X. (2019a). Flaxseed fat-reducing yogurt nutrition bar and a preparation method thereof. CN 201910603833.X., bTang, Z. X. (2019b). Flaxseed yogurt for women and a making method thereof. CN 201910814791.; Tang et al., 2020Tang, Z. X., Shi, L. E., Wang, X. M., Dai, G. W., Cheng, L. A., Wan, Z. X., He, H., Wu, Q., Wang, Y. B., Jin, X. Y., Ying, R. F., & Huang, L. H. (2020). Whole flaxseed-based products and their health benefits. Food Science and Technology Research, 26(5), 561-578. http://dx.doi.org/10.3136/fstr.26.561.
http://dx.doi.org/10.3136/fstr.26.561...
, 2021Tang, Z. X., Ying, R. F., Lv, B. F., Yang, L. H., Xu, Z., Yan, L. Q., Bu, J. Z., & Wei, Y. S. (2021). Flaxseed oil: extraction, health benefits and products. Quality Assurance and Safety of Crops & Foods, 13(1), 1-19. http://dx.doi.org/10.15586/qas.v13i1.783.
http://dx.doi.org/10.15586/qas.v13i1.783...
). As for flaxseed protein, the studies are relatively limited due to anti-nutritional substances in flaxseed meal (Safdar et al., 2020Safdar, B., Pang, Z., Liu, X., Rashid, M. T., & Jatoi, M. A. (2020). Structural and functional properties of raw and defatted flaxseed flour and degradation of cyanogenic contents using different processing methods. Journal of Food Process Engineering, 43(6), e13406. http://dx.doi.org/10.1111/jfpe.13406.
http://dx.doi.org/10.1111/jfpe.13406...
). Moreover, because the potential health values of flaxseed proteins are not investigated sufficiently, flaxseed protein is generally used as a feed additive, not as one kind of food protein sources (Kuang et al., 2020Kuang, X., Kong, Y., Hu, X., Li, K., Guo, X., Liu, C., Han, L., & Li, D. (2020). Defatted flaxseed flour improves weight loss and lipid profile in overweight and obese adults: a randomized controlled trial. Food & Function, 11(9), 8237-8247. http://dx.doi.org/10.1039/D0FO00838A. PMid:32966475.
http://dx.doi.org/10.1039/D0FO00838A...
; Logarušić et al., 2020Logarušić, M., Radošević, K., Bis, A., Panić, M., Slivac, I., & Srček, V. G. (2020). Biological potential of flaxseed protein hydrolysates obtained by different proteases. Plant Foods for Human Nutrition, 75(4), 518-524. http://dx.doi.org/10.1007/s11130-020-00841-z. PMid:32766942.
http://dx.doi.org/10.1007/s11130-020-008...
).

Amino acids are necessary to support our growth. Although most of amino acids can be synthesized in our body, only nine kinds of essential amino acids (EAA) must be supplied through the diet. Flaxseed protein has the similar EAA profiles with soybean protein, but is inferior to egg protein (Bekhit et al., 2018Bekhit, A. E. A., Shavandi, A., Jodjaja, T., Birch, J., Teh, S., Ahmed, I. A. M., Al-Juhaimi, F. Y., Saeedi, P., & Bekhit, A. A. (2018). Flaxseed: composition, deoxification, utilization, and opportunities. Biocatalysis and Agricultural Biotechnology, 13, 129-152. http://dx.doi.org/10.1016/j.bcab.2017.11.017.
http://dx.doi.org/10.1016/j.bcab.2017.11...
; Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Udenigwe & Aluko, 2011Udenigwe, C. C., & Aluko, R. E. (2011). Another side of flaxseed proteins and peptides. Agro Food Industry Hi-Tech, 22, 50-53.). Marambe et al. (2011)Marambe, H. K., Shand, P. J., & Wanasundara, J. P. D. (2011). Release of angiotensin I-converting enzyme inhibitory peptides from flaxseed (Linum usitatissimum L.) protein under simulated gastrointestinal digestion. Journal of Agricultural and Food Chemistry, 59(17), 9596-9604. http://dx.doi.org/10.1021/jf202000e. PMid:21776963.
http://dx.doi.org/10.1021/jf202000e...
reported that flaxseed protein had around 34.3% EAA, providing a great potential for taking flaxseed as one kind of protein sources. Flaxseed protein (or meal) is abundant of branched-chain amino acids (valine and leucine) and aromatic amino acids (tyrosine and phenylalanine) (Oomah, 2001Oomah, B. D. (2001). Flaxseed as a functional food source. Journal of the Science of Food and Agriculture, 81(9), 889-894. http://dx.doi.org/10.1002/jsfa.898.
http://dx.doi.org/10.1002/jsfa.898...
; Zardo et al., 2009Zardo, D. M., Dantas, A. P., Vanz, R., Wosiacki, G., & Nogueira, A. (2009). Intensity of red pigmentation in apples and its influence on phenolic compounds content and antioxidant activity. Food Science and Technology, 29(1), 148-154. http://dx.doi.org/10.1590/S0101-20612009000100023.
http://dx.doi.org/10.1590/S0101-20612009...
). Thus, flaxseed protein can be utilized to develop flaxseed-based functional foods. Recently, the effect of the processing treatments on functional characteristics of flaxseed protein and the development of flaxseed protein in foods have been studied (Lan et al., 2020Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
; Nwachukwu & Aluko, 2018bNwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
; Tirgar et al., 2017Tirgar, M., Silcock, P., Carne, A., & Birch, E. J. (2017). Effect of extraction method on functional properties of flaxseed protein concentrates. Food Chemistry, 215, 417-424. http://dx.doi.org/10.1016/j.foodchem.2016.08.002. PMid:27542494.
http://dx.doi.org/10.1016/j.foodchem.201...
; Wanasundara & Shahidi, 2003Wanasundara, P. K. J. P. D., & Shahidi, F. (2003). Flaxseed proteins: potential food applications and process-induced changes. In L. U. Thompson & S. C. Cunnane (Eds.), Flaxseed in human nutrition (pp. 387-403). Champaign: AOCS Press. http://dx.doi.org/10.1201/9781439831915.ch21.
http://dx.doi.org/10.1201/9781439831915....
). An increasing number of evidence have demonstrated that flaxseed protein and its hydrolysates exhibit many health promoting benefits (Franck et al., 2019Franck, M., Perreault, V., Suwal, S., Marciniak, A., Bazinet, L., & Doyen, A. (2019). High hydrostatic pressure-assisted enzymatic hydrolysis improved protein digestion of flaxseed protein isolate and generation of peptides with antioxidant activity. Food Research International, 115, 467-473. http://dx.doi.org/10.1016/j.foodres.2018.10.034. PMid:30599966.
http://dx.doi.org/10.1016/j.foodres.2018...
; Marie et al., 2019Marie, G. C. U., Perreault, V., Henaux, L., Carnovale, V., Aluko, R. E., Marette, A., Doyen, A., & Bazinet, L. (2019). Impact of a high hydrostatic pressure pretreatment on the separation of bioactive peptides from flaxseed protein hydrolysates by electrodialysis with ultrafiltration membranes. Separation and Purification Technology, 211, 242-251. http://dx.doi.org/10.1016/j.seppur.2018.09.063.
http://dx.doi.org/10.1016/j.seppur.2018....
; Nwachukwu & Aluko, 2018aNwachukwu, I. D., & Aluko, R. E. (2018a). Antioxidant properties of flaxseed protein hydrolysates: influence of hydrolytic enzyme concentration and peptide size. Journal of the American Oil Chemists’ Society, 95(8), 1105-1118. http://dx.doi.org/10.1002/aocs.12042.
http://dx.doi.org/10.1002/aocs.12042...
; Shi et al., 2021Shi, J., Xiao, J., Liu, L., & Dong, X. (2021). Ultrasonic assisted oil-in-water emulsions stabilized by flaxseed protein isolate: influence of different oils. Journal of Dispersion Science and Technology, 1-12. http://dx.doi.org/10.1080/01932691.2021.1880923.
http://dx.doi.org/10.1080/01932691.2021....
; Wei et al., 2018Wei, C. K., Thakur, K., Liu, D. H., Zhang, J. G., & Wei, Z. J. (2018). Enzymatic hydrolysis of flaxseed (Linum usitatissimum L.) protein and sensory characterization of Maillard reaction products. Food Chemistry, 263, 186-193. http://dx.doi.org/10.1016/j.foodchem.2018.04.120. PMid:29784306.
http://dx.doi.org/10.1016/j.foodchem.201...
). Therefore, to increase the added value of flaxseed protein, we showed a review of the latest development of extraction, functionalities and applications of flaxseed protein in this paper. The preparation of flaxseed protein hydrolysates was also presented.

2 Nutritional properties of flaxseed and its protein

The concentration of the compositions in flaxseed varies widely, which is dependent on many factors, such as cultivars, growing environments. Generally, the contents of flaxseed oil, dietary fibre, protein, and lignan, are 38-45%, 18-28%, 20-28%, and 0.8-1.3%, respectively (Rabetafika et al., 2011Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x.
http://dx.doi.org/10.1111/j.1365-2621.20...
; Tang et al., 2020Tang, Z. X., Shi, L. E., Wang, X. M., Dai, G. W., Cheng, L. A., Wan, Z. X., He, H., Wu, Q., Wang, Y. B., Jin, X. Y., Ying, R. F., & Huang, L. H. (2020). Whole flaxseed-based products and their health benefits. Food Science and Technology Research, 26(5), 561-578. http://dx.doi.org/10.3136/fstr.26.561.
http://dx.doi.org/10.3136/fstr.26.561...
, 2021Tang, Z. X., Ying, R. F., Lv, B. F., Yang, L. H., Xu, Z., Yan, L. Q., Bu, J. Z., & Wei, Y. S. (2021). Flaxseed oil: extraction, health benefits and products. Quality Assurance and Safety of Crops & Foods, 13(1), 1-19. http://dx.doi.org/10.15586/qas.v13i1.783.
http://dx.doi.org/10.15586/qas.v13i1.783...
). The composition of whole flaxseed was showed in Table 1. The level of flaxseed protein in whole flaxseed changes widely from 10 to 31%, which depends on many factors, for example cultivars, environmental conditions and processing methods (Chung et al., 2005Chung, M. W. Y., Lei, B., & Li-Chan, E. C. Y. (2005). Isolation and structural characterization of the major protein fraction from NorMan flaxseed (Linum usitatissimum L.). Food Chemistry, 90(1-2), 271-279. http://dx.doi.org/10.1016/j.foodchem.2003.07.038.
http://dx.doi.org/10.1016/j.foodchem.200...
). Flaxseed protein mainly consists of 11-12S globulin and 1.6-2S albumin. 11-12S globulin, a salt-soluble protein, has high molecular weight (252-298 kDa), whereas 1.6-2S albumin, a water-soluble protein, exhibits low molecular weight (16-17 kDa) (Arntfield, 2018Arntfield, S. D. (2018). Proteins from oil-producing plants. In Y. D. Rada (Ed.), Proteins in food processing (pp. 187-221). UK: Woodhead publications. http://dx.doi.org/10.1016/B978-0-08-100722-8.00008-5.
http://dx.doi.org/10.1016/B978-0-08-1007...
; Sammour et al., 1994Sammour, R. H., El-Shourbagy, M. N., Abo-Shady, A. M., & Abasary, A. M. (1994). The seed proteins of linseed (Linum usitativissimum L.). Bulletin of Botany Academia Sinica, 35, 171-177.; Sammour, 1999Sammour, R. H. (1999). Proteins of linseed (Linum usitatissimum L.), extraction and characterization by electrophoresis. Botanical Bulletin of Academia Sinica, 40, 121-126.). 11-12S globulin named as linin, accounts for 64–85% of total flaxseed protein (Arntfield, 2018Arntfield, S. D. (2018). Proteins from oil-producing plants. In Y. D. Rada (Ed.), Proteins in food processing (pp. 187-221). UK: Woodhead publications. http://dx.doi.org/10.1016/B978-0-08-100722-8.00008-5.
http://dx.doi.org/10.1016/B978-0-08-1007...
; Lei et al., 2003Lei, B., Li-Chan, E. C. Y., Oomah, B. D., & Mazza, G. (2003). Distribution of cadmium-binding components in flax (Linum usitatissimum L.) seed. Journal of Agricultural and Food Chemistry, 51(3), 814-821. http://dx.doi.org/10.1021/jf0209084. PMid:12537463.
http://dx.doi.org/10.1021/jf0209084...
; Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
). 11S globulin has four subunits (36, 46, 50, and 55 kDa), which are linked by disulfide bonds (Krause et al., 2010Krause, J. P., Schultz, M., & Dudek, S. (2010). Effect of extraction conditions on composition, surface activity and rheological properties of protein isolations from flaxseed (Linum usitativissimum L.). Journal of the Science of Food and Agriculture, 82(9), 970-976. http://dx.doi.org/10.1002/jsfa.1140.
http://dx.doi.org/10.1002/jsfa.1140...
). 1.6-2S albumin of flaxseed protein termed as colinin, has a single polypeptide chain with 168 or 169 amino acids, and is occupied for about 40-42% of flaxseed protein (Bekhit et al., 2018Bekhit, A. E. A., Shavandi, A., Jodjaja, T., Birch, J., Teh, S., Ahmed, I. A. M., Al-Juhaimi, F. Y., Saeedi, P., & Bekhit, A. A. (2018). Flaxseed: composition, deoxification, utilization, and opportunities. Biocatalysis and Agricultural Biotechnology, 13, 129-152. http://dx.doi.org/10.1016/j.bcab.2017.11.017.
http://dx.doi.org/10.1016/j.bcab.2017.11...
; Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Sammour, 1999Sammour, R. H. (1999). Proteins of linseed (Linum usitatissimum L.), extraction and characterization by electrophoresis. Botanical Bulletin of Academia Sinica, 40, 121-126.). Compared to 11-12S globulin, 1.6-2S albumin possesses a much more ordered structure and more disulfide linkages (Bakowska-Barczak et al., 2020Bakowska-Barczak, A., Larminat, M. A., & Kolodziejczyk, P. P. (2020). The application of flax and hempseed in food, nutraceutical and personal care products. In R. M. Kozlowski & M. M. Talarczyk (Eds.), Handbook of natural fibers (pp. 557-590). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-818782-1.00017-1.
http://dx.doi.org/10.1016/B978-0-12-8187...
).

Table 1
Nutritional composition of whole flaxseed.

Many factors, for instance flaxseed cultivars, environmental conditions, and processing conditions, can affect amino acid profiles of flaxseed protein (Dash et al., 2021Dash, K. K., Kumar, A., Kumari, S., & Malik, M. A. (2021). Silver nanoparticle incorporated flaxseed-alginate composite films: effect of physicochemical, mechanical, and thermal properties. Journal of Polymers and the Environment, 29(11), 3649-3659. http://dx.doi.org/10.1007/s10924-021-02137-y.
http://dx.doi.org/10.1007/s10924-021-021...
). The amino acid compositions of flaxseed protein were showed in Table 2. Flaxseed protein is enriched in arginine, aspartic acid, and glutamic acid, whereas it is poor in sulphur-containing amino acids, for example methionine, cysteine (Hall et al., 2006Hall, C., Tulbek, M. C., & Xu, Y. (2006). Flaxseed. In S. L. Taylor (Ed.), Advance in food and nutrition research (pp. 1-97). Boston: Elsevier.; Juodeikiene, et al., 2020Juodeikiene, G., Zadeike, D., Trakselyte-Rupsiene, K., Gasauskaite, K., Bartkiene, E., Lele, V., Viskelis, P., Bernatoniene, J., Ivanauskas, L., & Jakstas, V. (2020). Functionalisation of flaxseed proteins assisted by ultrasonication to produce coatings enriched with raspberries phytochemicals. Lebensmittel-Wissenschaft + Technologie, 124, 109180. http://dx.doi.org/10.1016/j.lwt.2020.109180.
http://dx.doi.org/10.1016/j.lwt.2020.109...
; Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Oomah & Mazza, 1993Oomah, B. D., & Mazza, G. (1993). Processing of flaxseed meal: effect of solvent extraction on physicochemical characteristics. Lebensmittel-Wissenschaft + Technologie, 26(4), 312-317. http://dx.doi.org/10.1006/fstl.1993.1064.
http://dx.doi.org/10.1006/fstl.1993.1064...
). Lysine is generally considered as the limiting amino acid (Table 2; Chung et al., 2005Chung, M. W. Y., Lei, B., & Li-Chan, E. C. Y. (2005). Isolation and structural characterization of the major protein fraction from NorMan flaxseed (Linum usitatissimum L.). Food Chemistry, 90(1-2), 271-279. http://dx.doi.org/10.1016/j.foodchem.2003.07.038.
http://dx.doi.org/10.1016/j.foodchem.200...
). Therefore, before starting the development of flaxseed protein-based foods, we should know that flaxseed protein can only satisfy the amino acid nutritional requirements for the adults. It is not a good protein source for baby due to the limited amino acid levels of lysine (Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Udenigwe & Aluko, 2011Udenigwe, C. C., & Aluko, R. E. (2011). Another side of flaxseed proteins and peptides. Agro Food Industry Hi-Tech, 22, 50-53.). In order to make up for the deficiency of lysine in flaxseed protein, the complementary proteins enriched with lysine should be added. Germination can significantly change the contents of amino acids in flaxseed (Lv & Huang, 2015Lv, B., & Huang, C.X. (2015). Flaxseed sprouted powder and a preparation method thereof. CN 201510030685: A.). Wanasundara et al. (1999)Wanasundara, P. K. J. P. D., Wanasundara, U. N., & Shahidi, F. (1999). Changes in flax (Linum usitatissimum L.) seed lipids during germination. Journal of the American Oil Chemists’ Society, 76(1), 41-48. http://dx.doi.org/10.1007/s11746-999-0045-z.
http://dx.doi.org/10.1007/s11746-999-004...
found that the total amino acids concentration in flaxseed increased by around 15 times after an 8-day of germination. The contents of glutamine and leucine were significantly improved.

Table 2
Amino acid composition of flaxseed protein.

3 Extraction of flaxseed protein

At present, most studies regarding extraction processes for flaxseed protein are at a laboratory scale. The major obstacle to extract flaxseed protein is the mucilage distributed in the outer layer of flaxseed (Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
). The mucilage can improve the extract viscosity, and thus decreases the extraction efficiency. Therefore, some attempts, such as enzymatic or physicochemical ways, have been adopted to remove or reduce the mucilage level before flaxseed protein extraction is carried out (Liu et al., 2018Liu, J., Shim, Y. Y., Tse, T. J., Wang, Y., & Reaney, M. J. T. (2018). Flaxseed gum a versatile natural hydrocolloid for food and non-food applications. Trends in Food Science & Technology, 75, 146-157. http://dx.doi.org/10.1016/j.tifs.2018.01.011.
http://dx.doi.org/10.1016/j.tifs.2018.01...
; Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
). The physical dehulling for flaxseed is one of the pretreatment processes to extract flaxseed protein. Wet and dry extraction methods have been developed to remove flaxseed mucilage (Karaca et al., 2011Karaca, A. C., Low, N., & Nickerson, M. (2011). Emulsifying properties of canola and flaxseed protein isolates produced by isoelectric precipitation and salt extraction. Food Research International, 44(9), 2991-2998. http://dx.doi.org/10.1016/j.foodres.2011.07.009.
http://dx.doi.org/10.1016/j.foodres.2011...
; Kaushik et al., 2016Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106. PMid:26616943.
http://dx.doi.org/10.1016/j.foodchem.201...
; Lan et al., 2020Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
; Mridula et al., 2014Mridula, D., Barnwal, P., Gurumayum, S., & Singh, K. K. (2014). Effect of chemical pretreatment on dehulling parameters of flaxseed (cv. Garima). Journal of Food Science and Technology, 51(9), 2228-2233. http://dx.doi.org/10.1007/s13197-012-0699-7. PMid:25190888.
http://dx.doi.org/10.1007/s13197-012-069...
). The dehulling efficiency is highly influenced by various factors, for example the speed, dehulling time, and the moisture in flaxseed (Zheng et al., 2003Zheng, Y. I., Wiesenborn, D. P., Tostenson, K., & Kangas, N. (2003). Screw pressing of whole and dehulled flaxseed for organic oil. Journal of the American Oil Chemists’ Society, 80(10), 1039-1045. http://dx.doi.org/10.1007/s11746-003-0817-7.
http://dx.doi.org/10.1007/s11746-003-081...
). Due to multiple steps involved in wet extraction process, wet process is not economical to extract flaxseed protein. Currently, the main dehulling method is a dry extraction process (Li & Hao, 2013Li, T., & Hao, J. (2013). A peeling method and machine for flaxseeds. CN: 201310630673: A.). The method that using polysaccharide-degrading enzymes to degrade the mucilage in flaxseed, has been investigated by some researchers. Through the combination of NaHCO3 soaking and Viscozyme (Novozyme, 100 Fungal β glucanase/g) to treat whole flaxseed, protein extraction efficiency could be improved significantly compared to only NaHCO3 soaking to treat whole flaxseed (Slominski et al., 2006Slominski, B. A., Meng, X., Campbell, L. D., Guenter, W., & Jones, O. (2006). The use of enzyme technology for improved energy utilization from full-fat oilseeds. Part II: Flaxseed. Poultry Science, 85(6), 1031-1037. http://dx.doi.org/10.1093/ps/85.6.1031. PMid:16776472.
http://dx.doi.org/10.1093/ps/85.6.1031...
; Wanasundara & Shahidi, 1997Wanasundara, P. K. J. P. D., & Shahidi, F. (1997). Removal of flaxseed mucilage by chemical and enzymatic treatments. Food Chemistry, 59(1), 47-55. http://dx.doi.org/10.1016/S0308-8146(96)00093-3.
http://dx.doi.org/10.1016/S0308-8146(96)...
). Song et al. (2017)Song, X., Zhang, L., Jing, C., Kang, Q., Wu, G., Jiang, W., & Yuan, H. (2017). Study on degumming process of flaxseed by enzymatic hydrolysis. Heilongjiang Nongye Kexue, 12, 67-69. also showed that the de-mucilaged rate could be reached to 94.7% under the optimized pectinase hydrolysis conditions.

Protein concentration in defated flaxseed meal (DFM), the by-product of flaxseed pressing, usually changes from 35 to 40%, that indicates that DFM is an excellent source to obtain flaxseed protein (Lan et al., 2020Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
; Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Nwachukwu & Aluko, 2018bNwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
; Sa et al., 2021Sa, A. G. A., Silva, D. G., Pacheco, M. T. B., Moreno, Y. M. F., & Carciofi, B. A. M. (2021). Oilseed by-products as plant-based protein sources: amino acid profile and digestibility. Future Foods, 3, 100023. http://dx.doi.org/10.1016/j.fufo.2021.100023.
http://dx.doi.org/10.1016/j.fufo.2021.10...
; Tang et al., 2021Tang, Z. X., Ying, R. F., Lv, B. F., Yang, L. H., Xu, Z., Yan, L. Q., Bu, J. Z., & Wei, Y. S. (2021). Flaxseed oil: extraction, health benefits and products. Quality Assurance and Safety of Crops & Foods, 13(1), 1-19. http://dx.doi.org/10.15586/qas.v13i1.783.
http://dx.doi.org/10.15586/qas.v13i1.783...
; Tirgar et al., 2017Tirgar, M., Silcock, P., Carne, A., & Birch, E. J. (2017). Effect of extraction method on functional properties of flaxseed protein concentrates. Food Chemistry, 215, 417-424. http://dx.doi.org/10.1016/j.foodchem.2016.08.002. PMid:27542494.
http://dx.doi.org/10.1016/j.foodchem.201...
). Some processing factors, such as solvent composition, pH, heating treatment, solvent/meal ratio, and salt concentration, can significantly affect the solubility of flaxseed protein (Tirgar et al., 2017Tirgar, M., Silcock, P., Carne, A., & Birch, E. J. (2017). Effect of extraction method on functional properties of flaxseed protein concentrates. Food Chemistry, 215, 417-424. http://dx.doi.org/10.1016/j.foodchem.2016.08.002. PMid:27542494.
http://dx.doi.org/10.1016/j.foodchem.201...
). Many methods, such as alkali-aided solubilization/isoelectric precipitation, buffered salt or polyphosphate extraction, micellization, have been developed to extract flaxseed protein (Kaushik et al., 2016Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106. PMid:26616943.
http://dx.doi.org/10.1016/j.foodchem.201...
; Nwachukwu & Aluko, 2018bNwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
; Pham et al., 2019bPham, L. B., Wang, B., Zisu, B., & Adhikari, B. (2019b). Covalent modification of flaxseed protein isolate by phenolic compounds and the structure and functional properties of the adducts. Food Chemistry, 293, 463-471. http://dx.doi.org/10.1016/j.foodchem.2019.04.123. PMid:31151635.
http://dx.doi.org/10.1016/j.foodchem.201...
; Teh et al., 2014Teh, S. S., Bekhit, E. D., Carne, A., & Birch, J. (2014). Effect of the defatting process, acid and alkali extraction on the physicochemical and functional properties of hemp, flax and canola seed cake protein isolates. Journal of Food Measurement and Characterization, 8(2), 92-104. http://dx.doi.org/10.1007/s11694-013-9168-x.
http://dx.doi.org/10.1007/s11694-013-916...
). Some of these methods used to obtain flaxseed protein were given in Table 3. Of all employed methods, alkali extraction is one of the most popular methods. As most of oilseed proteins, flaxseed protein is soluble at alkaline conditions. Flaxseed protein can be extracted from DFM at pH values from 8.5 to 11.0 or under the existence of NaCl. However, the extraction at extreme alkaline conditions may cause undesirable modification of proteins, and even unpredicatable reactions. Therefore, the extraction pH for flaxseed protein is preferred from 7.0 to 9.0 (Pham et al., 2019bPham, L. B., Wang, B., Zisu, B., & Adhikari, B. (2019b). Covalent modification of flaxseed protein isolate by phenolic compounds and the structure and functional properties of the adducts. Food Chemistry, 293, 463-471. http://dx.doi.org/10.1016/j.foodchem.2019.04.123. PMid:31151635.
http://dx.doi.org/10.1016/j.foodchem.201...
). After flaxseed protein is extracted in alkali solutions, pH needs to be adjusted to close to isoelectronic point (between 3.5 and 4.4) (Karaca et al., 2011Karaca, A. C., Low, N., & Nickerson, M. (2011). Emulsifying properties of canola and flaxseed protein isolates produced by isoelectric precipitation and salt extraction. Food Research International, 44(9), 2991-2998. http://dx.doi.org/10.1016/j.foodres.2011.07.009.
http://dx.doi.org/10.1016/j.foodres.2011...
; Lan et al., 2020Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
; Nasrabadi et al., 2019Nasrabadi, M. N., Goli, S. A. H., Doost, A. S., Roman, B., Dewettinck, K., Stevens, C. V., & Van Der Meeren, P. V. (2019). Plant based pickering stabilization of emulsions using soluble flaxseed protein and mucilage nano-assemblies. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 563, 170-182. http://dx.doi.org/10.1016/j.colsurfa.2018.12.004.
http://dx.doi.org/10.1016/j.colsurfa.201...
). Alkaline-aided extraction/isoelectric precipitation method is not suitable to extract flaxseed protein as the mucilage in flaxseed hull may disturb the protein precipitation. In the study of Kaushik et al. (2016)Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106. PMid:26616943.
http://dx.doi.org/10.1016/j.foodchem.201...
, the de-mucilaged DFM was soaked in pH 8.6 tris buffer for 24 h, and then flaxseed protein was precipitated after pH was adjusted to pH 4.2.

Table 3
The extraction for flaxseed protein.

Nwachukwu & Aluko (2018b)Nwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
obtained flaxseed albumin and globulin after DFM was extracted with NaCl for 1 h at room temperature. Perreault et al. (2017)Perreault, V., Henaux, L., Bazinet, L., & Doyen, A. (2017). Pretreatment of flaxseed protein isolate by high hydrostatic pressure: impacts on protein structure, enzymatic hydrolysis and final hydrolysate antioxidant capacities. Food Chemistry, 221, 1805-1812. http://dx.doi.org/10.1016/j.foodchem.2016.10.100. PMid:27979166.
http://dx.doi.org/10.1016/j.foodchem.201...
also extracted flaxseed protein isolate from DFM. In their study, pH of flaxseed extracts was adjusted to 5.0, afterwards cellulase was added in order to hydrolyze the fibers. Flaxseed protein content could reach up to 82%. Ribeiro et al. (2013)Ribeiro, B. D., Barreto, D. W., & Coelho, M. A. (2013). Enzyme-enhanced extraction of phenolic compounds and proteins from flaxseed meal. ISRN Biotechnology, 2013, 521067. http://dx.doi.org/10.5402/2013/521067. PMid:25969774.
http://dx.doi.org/10.5402/2013/521067...
used the enzyme-assisted method to extract flaxseed protein. The yield of flaxseed protein (15.2%) was obtained when DFM was agitated at the speed of 200 rpm, and treated by the mixture of ultrazyme, viscozyme and alcalase under 50 °C for 1.5 h. Tirgar et al. (2017)Tirgar, M., Silcock, P., Carne, A., & Birch, E. J. (2017). Effect of extraction method on functional properties of flaxseed protein concentrates. Food Chemistry, 215, 417-424. http://dx.doi.org/10.1016/j.foodchem.2016.08.002. PMid:27542494.
http://dx.doi.org/10.1016/j.foodchem.201...
found that the higher flaxseed protein content (86.8%) could be obtained by employing the combination of an alkaline-aided/isoelectric precipitation plus the treatment of cellulase extraction/ethanol precipitation for the extracts, compared to alkaline-aided/isoelectric precipitation or cellulase treatment alone.

4 Functional properties of flaxseed protein

As other oilseed proteins, flaxseed protein exhibits many functional characteristics, for example water/oil adsorption ability, solubility, emulsion capacity, and foaming capacity (Mohamed et al., 2020Mohamed, R. S., Fouda, K., & Akl, E. M. (2020). Hepatorenal protective effect of flaxseed protein isolate incorporated in lemon juice against lead toxicity in rats. Toxicology Reports, 7, 30-35. http://dx.doi.org/10.1016/j.toxrep.2019.12.001. PMid:31890606.
http://dx.doi.org/10.1016/j.toxrep.2019....
; Sharma & Saini, 2021Sharma, M., & Saini, C. S. (2021). Postharvest shelf-life extension of fresh-cut guavas (Psidium guajava) using flaxseed protein-based composite coatings. Food Hydrocolloids for Health, 1, 100015. http://dx.doi.org/10.1016/j.fhfh.2021.100015.
http://dx.doi.org/10.1016/j.fhfh.2021.10...
; Shi et al., 2021Shi, J., Xiao, J., Liu, L., & Dong, X. (2021). Ultrasonic assisted oil-in-water emulsions stabilized by flaxseed protein isolate: influence of different oils. Journal of Dispersion Science and Technology, 1-12. http://dx.doi.org/10.1080/01932691.2021.1880923.
http://dx.doi.org/10.1080/01932691.2021....
; Wang et al., 2010Wang, B., Li, D., Wang, L., & Özkan, N. (2010). Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions. Journal of Food Engineering, 96(4), 555-561. http://dx.doi.org/10.1016/j.jfoodeng.2009.09.001.
http://dx.doi.org/10.1016/j.jfoodeng.200...
). These characteristics are significantly affected by various factors including temperature, ionic strength, pH, the methods used for protein extraction, purity and particle size of the proteins (Krause et al., 2010Krause, J. P., Schultz, M., & Dudek, S. (2010). Effect of extraction conditions on composition, surface activity and rheological properties of protein isolations from flaxseed (Linum usitativissimum L.). Journal of the Science of Food and Agriculture, 82(9), 970-976. http://dx.doi.org/10.1002/jsfa.1140.
http://dx.doi.org/10.1002/jsfa.1140...
; Martínez-Flores et al., 2006Martínez-Flores, H., Barrera, E., Garnica-Romo, M., Penagos, C., Saavedra, J., & Macazaga-Alvarez, R. (2006). Functional characteristics of protein flaxseed concentrate obtained applying a response surface methodology. Journal of Food Science, 71(8), 495-498. http://dx.doi.org/10.1111/j.1750-3841.2006.00147.x.
http://dx.doi.org/10.1111/j.1750-3841.20...
; Tirgar et al., 2017Tirgar, M., Silcock, P., Carne, A., & Birch, E. J. (2017). Effect of extraction method on functional properties of flaxseed protein concentrates. Food Chemistry, 215, 417-424. http://dx.doi.org/10.1016/j.foodchem.2016.08.002. PMid:27542494.
http://dx.doi.org/10.1016/j.foodchem.201...
). The mucilage in flaxseed protein samples may affect functional properties of flaxseed protein (Rabetafika et al., 2011Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x.
http://dx.doi.org/10.1111/j.1365-2621.20...
). It can improve water adsorption, the foaming and emulsifying properties of flaxseed protein, but, it decreases oil adsorption capacity of flaxseed protein (Lipilina & Ganji, 2009Lipilina, E., & Ganji, V. (2009). Incorporation of ground flaxseed into bakery products and its effect on sensory and nutritional characteristics: a pilot study. Journal of Food Service, 20(1), 52-59. http://dx.doi.org/10.1111/j.1748-0159.2008.00124.x.
http://dx.doi.org/10.1111/j.1748-0159.20...
; Rabetafika et al., 2011Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x.
http://dx.doi.org/10.1111/j.1365-2621.20...
).

4.1 Thermal denaturation

The functional properties of plant proteins are highly related to their structures. As other oilseed proteins, the heating can alter the structure of flaxseed protein, and results in the change of functional characteristics of flaxseed protein. Kaushik et al. (2016)Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106. PMid:26616943.
http://dx.doi.org/10.1016/j.foodchem.201...
showed that flaxseed protein underwent two structural transitions during the heating. One was observed at a temperature around 53.72 °C, the other was around 105.05 °C. Safdar et al. (2020)Safdar, B., Pang, Z., Liu, X., Rashid, M. T., & Jatoi, M. A. (2020). Structural and functional properties of raw and defatted flaxseed flour and degradation of cyanogenic contents using different processing methods. Journal of Food Process Engineering, 43(6), e13406. http://dx.doi.org/10.1111/jfpe.13406.
http://dx.doi.org/10.1111/jfpe.13406...
observed two endothermic peaks temperatures of defatted flaxseed flour at 88.49 °C, 223.84 °C. Generally, the peaks around 100 °C are related to the loss of water and initial denaturation of flaxseed protein. Similarly, Sharma & Saini (2021)Sharma, M., & Saini, C. S. (2021). Postharvest shelf-life extension of fresh-cut guavas (Psidium guajava) using flaxseed protein-based composite coatings. Food Hydrocolloids for Health, 1, 100015. http://dx.doi.org/10.1016/j.fhfh.2021.100015.
http://dx.doi.org/10.1016/j.fhfh.2021.10...
reported the denaturation temperature of flaxseed protein isolates obtained by alkali-aided solubilization/isoelectric precipitation, was 82.52 °C. Lan et al. (2020)Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
showed that flaxseed protein concentrates showed better heating stability, and had higher denaturation temperature, compared to flaxseed protein isolates.

4.2 Water/oil absorbing capacity

Water and oil adsorbing capacities of flaxseed protein isolate could be comparable to those of other oilseed proteins (Kaushik et al., 2016Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106. PMid:26616943.
http://dx.doi.org/10.1016/j.foodchem.201...
). Kaushik et al. (2016)Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106. PMid:26616943.
http://dx.doi.org/10.1016/j.foodchem.201...
reported water/oil absorbing ability of flaxseed protein isolate was higher than that of most of the investigated proteins including soy protein, gelatin. The higher oil absorbing capacity of flaxseed protein isolate was attributed to their greater lipophilic property. Mohamed et al. (2020)Mohamed, R. S., Fouda, K., & Akl, E. M. (2020). Hepatorenal protective effect of flaxseed protein isolate incorporated in lemon juice against lead toxicity in rats. Toxicology Reports, 7, 30-35. http://dx.doi.org/10.1016/j.toxrep.2019.12.001. PMid:31890606.
http://dx.doi.org/10.1016/j.toxrep.2019....
reported water holding ability of flaxseed protein isolate was 11.4 g/g, while oil holding ability of flaxseed protein isolate was 1.47 g/g. In the study of Sharma & Saini (2021)Sharma, M., & Saini, C. S. (2021). Postharvest shelf-life extension of fresh-cut guavas (Psidium guajava) using flaxseed protein-based composite coatings. Food Hydrocolloids for Health, 1, 100015. http://dx.doi.org/10.1016/j.fhfh.2021.100015.
http://dx.doi.org/10.1016/j.fhfh.2021.10...
, water and oil holding abilities of flaxseed protein isolate were reported to be 2.85 g/g and 3.86 g/g, respectively. Oil adsorption capacity of food proteins is an important index for flavor retention and mouth-feel (Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
). Flaxseed protein can be incorporated into emulsion-type meat products due to its good oil adsorption capacity. During cooking, flaxseed protein also can reduce fat losses, and thus decreases the weight loss of the products. Oil adsorption capacity of flaxseed protein concentrate was poorer compared to that of soybean protein concentrate, while it was higher than that of amaranth protein concentrate (Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Martínez-Flores et al., 2006Martínez-Flores, H., Barrera, E., Garnica-Romo, M., Penagos, C., Saavedra, J., & Macazaga-Alvarez, R. (2006). Functional characteristics of protein flaxseed concentrate obtained applying a response surface methodology. Journal of Food Science, 71(8), 495-498. http://dx.doi.org/10.1111/j.1750-3841.2006.00147.x.
http://dx.doi.org/10.1111/j.1750-3841.20...
).

4.3 Emulsifying capacity

Flaxseed protein showed better emulsifying capacity compared to whey protein isolate and canola protein isolate, and a comparable creaming stability with canola and whey proteins (Karaca et al., 2011Karaca, A. C., Low, N., & Nickerson, M. (2011). Emulsifying properties of canola and flaxseed protein isolates produced by isoelectric precipitation and salt extraction. Food Research International, 44(9), 2991-2998. http://dx.doi.org/10.1016/j.foodres.2011.07.009.
http://dx.doi.org/10.1016/j.foodres.2011...
). Excessive heating treatment can destroy the structure of flaxseed protein, reduces the solubility, and thus significantly decreases emulsion capacity of flaxseed protein. Martínez-Flores et al. (2006)Martínez-Flores, H., Barrera, E., Garnica-Romo, M., Penagos, C., Saavedra, J., & Macazaga-Alvarez, R. (2006). Functional characteristics of protein flaxseed concentrate obtained applying a response surface methodology. Journal of Food Science, 71(8), 495-498. http://dx.doi.org/10.1111/j.1750-3841.2006.00147.x.
http://dx.doi.org/10.1111/j.1750-3841.20...
found that solvent, pH and temperature significantly affected emulsion capacity of flaxseed protein. Several studies indicated that alkali-solubilized flaxseed protein had high emulsifying capacity (Mueller et al., 2010Mueller, K., Eisner, P., Yoshie-Stark, Y., Nakada, R., & Kirchhoff, E. (2010). Functional properties and chemical composition of fractionated brown and yellow linseed meal (Linum usitatissimum L.). Journal of Food Engineering, 98(4), 453-460. http://dx.doi.org/10.1016/j.jfoodeng.2010.01.028.
http://dx.doi.org/10.1016/j.jfoodeng.201...
; Sharma & Saini, 2021Sharma, M., & Saini, C. S. (2021). Postharvest shelf-life extension of fresh-cut guavas (Psidium guajava) using flaxseed protein-based composite coatings. Food Hydrocolloids for Health, 1, 100015. http://dx.doi.org/10.1016/j.fhfh.2021.100015.
http://dx.doi.org/10.1016/j.fhfh.2021.10...
; Yoshie-Stark et al., 2011Yoshie-Stark, Y., Müller, K., Kawarada, H., Futagawa, K., Nakada, R., & Tashiro, Y. (2011). Functional properties of linseed meal fractions: application as nutraceutical ingredient. Food Science and Technology Research, 17(4), 301-310. http://dx.doi.org/10.3136/fstr.17.301.
http://dx.doi.org/10.3136/fstr.17.301...
). Tirgar et al. (2017)Tirgar, M., Silcock, P., Carne, A., & Birch, E. J. (2017). Effect of extraction method on functional properties of flaxseed protein concentrates. Food Chemistry, 215, 417-424. http://dx.doi.org/10.1016/j.foodchem.2016.08.002. PMid:27542494.
http://dx.doi.org/10.1016/j.foodchem.201...
found that alkali-solubilized flaxseed protein concentrate exhibited the highest emulsion capacity (87.91%) among the investigated proteins. The higher emulsion capacity of flaxseed protein concentrate was due to the high content of carbohydrate, compared to other protein concentrates which led to stabilize the emulsion efficiently. In addition, alkali-solubilized flaxseed protein concentrate showed the highest emulsion activity (87.1 m2/g). Kaushik et al. (2016)Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106. PMid:26616943.
http://dx.doi.org/10.1016/j.foodchem.201...
obtained flaxseed protein (around 90%) after flaxseed was de-mucilaged at 60 °C. The emulsion activity (375.5 m2/g) of flaxseed protein was higher compared to that of investigated proteins including whey protein, soy protein and gelatine. Besides, the emulsions stabilized by flaxseed protein isolate showed higher stability at low pHs than those stabilized by the studied other proteins. Nwachukwu & Aluko (2018b)Nwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
suggested that flaxseed globulin had better emulsifying property at alkaline conditions, whereas flaxseed albumin exhibited better emulsifying property at acid conditions. Therefore, due to the suitable emulsifying property and good thermal stability of flaxseed protein, it has been used as a promising wall material to encapsulate bioactives (Pham et al., 2020Pham, L. B., Wang, B., Zisu, B., Truong, T., & Adhikari, B. (2020). Microencapsulation of flaxseed oil using polyphenol-adducted flaxseed protein isolate-flaxseed gum complex coacervates. Food Hydrocolloids, 107, 105944. http://dx.doi.org/10.1016/j.foodhyd.2020.105944.
http://dx.doi.org/10.1016/j.foodhyd.2020...
).

Emulsifying capacity of flaxseed protein can be improved by structure modification, and the change of protein conformation (Juodeikiene et al., 2020Juodeikiene, G., Zadeike, D., Trakselyte-Rupsiene, K., Gasauskaite, K., Bartkiene, E., Lele, V., Viskelis, P., Bernatoniene, J., Ivanauskas, L., & Jakstas, V. (2020). Functionalisation of flaxseed proteins assisted by ultrasonication to produce coatings enriched with raspberries phytochemicals. Lebensmittel-Wissenschaft + Technologie, 124, 109180. http://dx.doi.org/10.1016/j.lwt.2020.109180.
http://dx.doi.org/10.1016/j.lwt.2020.109...
; Nie et al., 2021Nie, C., Qin, X., Duan, Z., Huang, S., Yu, X., Deng, Q., Xiang, Q., & Geng, F. (2021). Comparative structural and techno-functional elucidation of full-fat and defatted flaxseed extracts: implication of atmospheric pressure plasma jet. Journal of the Science of Food and Agriculture, 102(2), 823-835. PMid:34232506.; Pham et al., 2019aPham, L. B., Wang, B., Zisu, B., & Adhikari, B. (2019a). Complexation between flaxseed protein isolate and phenolic compounds: effect on interfacial, emulsifying and antioxidant properties of emulsions. Food Hydrocolloids, 94, 20-29. http://dx.doi.org/10.1016/j.foodhyd.2019.03.007.
http://dx.doi.org/10.1016/j.foodhyd.2019...
, bPham, L. B., Wang, B., Zisu, B., & Adhikari, B. (2019b). Covalent modification of flaxseed protein isolate by phenolic compounds and the structure and functional properties of the adducts. Food Chemistry, 293, 463-471. http://dx.doi.org/10.1016/j.foodchem.2019.04.123. PMid:31151635.
http://dx.doi.org/10.1016/j.foodchem.201...
; Wang et al., 2010Wang, B., Li, D., Wang, L., & Özkan, N. (2010). Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions. Journal of Food Engineering, 96(4), 555-561. http://dx.doi.org/10.1016/j.jfoodeng.2009.09.001.
http://dx.doi.org/10.1016/j.jfoodeng.200...
). Wanasundara & Shahidi (1997)Wanasundara, P. K. J. P. D., & Shahidi, F. (1997). Removal of flaxseed mucilage by chemical and enzymatic treatments. Food Chemistry, 59(1), 47-55. http://dx.doi.org/10.1016/S0308-8146(96)00093-3.
http://dx.doi.org/10.1016/S0308-8146(96)...
modified flaxseed protein by attaching acyl (acetyl or succinyl) groups, and showed that emulsion capacity of flaxseed protein with low degree of acetylation was higher compared to that of the unmodified. Nasrabadi et al. (2019)Nasrabadi, M. N., Goli, S. A. H., Doost, A. S., Roman, B., Dewettinck, K., Stevens, C. V., & Van Der Meeren, P. V. (2019). Plant based pickering stabilization of emulsions using soluble flaxseed protein and mucilage nano-assemblies. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 563, 170-182. http://dx.doi.org/10.1016/j.colsurfa.2018.12.004.
http://dx.doi.org/10.1016/j.colsurfa.201...
found that flaxseed protein-mulcilage complex nanoassemblies adsorbed onto the surface of emulsion could form a protecting coating to inhibit flocculation and coalescence, and thus improved the emulsion stability. Yu et al. (2020)Yu, X., Huang, S., Nie, C., Deng, Q., Zhai, Y., & Shen, R. (2020). Effects of atmospheric pressure plasma jet on the physicochemical, functional, and antioxidant properties of flaxseed protein. Journal of Food Science, 85(7), 2010-2019. http://dx.doi.org/10.1111/1750-3841.15184. PMid:32529640.
http://dx.doi.org/10.1111/1750-3841.1518...
also reported that emulsifying capacity of flaxseed protein was significantly improved following short time (5~15 s) treatment by atmospheric pressure plasma jet, which was among with the changes of spatial conformation of flaxseed protein.

4.4 Foaming property

As other oilseed proteins, foams are easily to be generated when flaxseed protein is whipped or stirred. Temperature and solvent pH significantly affect the foaming capacity and stability of flaxseed protein (Lan et al., 2020Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
). In general, the foaming properties of plant proteins are higher in the acid environment, and the weakest foaming properties are observed in around isoelectronic point of proteins (Lan et al., 2020Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
; Shevkani et al., 2015Shevkani, K., Singh, N., Kaur, A., & Rana, J. C. (2015). Structural and functional characterization of kidney bean and field pea protein isolates: a comparative study. Food Hydrocolloids, 43, 679-689. http://dx.doi.org/10.1016/j.foodhyd.2014.07.024.
http://dx.doi.org/10.1016/j.foodhyd.2014...
). Madhusudhan & Singh (1985aMadhusudhan, K. T., & Singh, N. (1985a). Effect of detoxification treatment on the physicochemical properties of linseed proteins. Journal of Agricultural and Food Chemistry, 33(6), 1219-1222. http://dx.doi.org/10.1021/jf00066a051.
http://dx.doi.org/10.1021/jf00066a051...
, bMadhusudhan, K. T., & Singh, N. (1985b). Isolation and characterization of the major fraction (12S) of linseed proteins. Journal of Agricultural and Food Chemistry, 33(4), 673-677. http://dx.doi.org/10.1021/jf00064a026.
http://dx.doi.org/10.1021/jf00064a026...
) found that foaming formation capacity of flaxseed protein was kept as an stable state at pH 2.0-6.0. The foaming formation capacity of flaxseed protein was significantly improved after pH was adjusted above 8.0. Foaming stability of flaxseed protein could remain unchanged until 45 °C. After mild heating treatment for flaxseed protein (45-80 °C), the forming stability was highly improved due to the exposition of the hydrophobic groups of flaxseed protein. If the temperature increased more than 80 °C, the foaming stability would decrease significantly because the solubility of flaxseed protein decreased (Bekhit et al., 2018Bekhit, A. E. A., Shavandi, A., Jodjaja, T., Birch, J., Teh, S., Ahmed, I. A. M., Al-Juhaimi, F. Y., Saeedi, P., & Bekhit, A. A. (2018). Flaxseed: composition, deoxification, utilization, and opportunities. Biocatalysis and Agricultural Biotechnology, 13, 129-152. http://dx.doi.org/10.1016/j.bcab.2017.11.017.
http://dx.doi.org/10.1016/j.bcab.2017.11...
).

High foaming capacity of flaxseed protein at pH 10 was observed by Martínez-Flores et al. (2006)Martínez-Flores, H., Barrera, E., Garnica-Romo, M., Penagos, C., Saavedra, J., & Macazaga-Alvarez, R. (2006). Functional characteristics of protein flaxseed concentrate obtained applying a response surface methodology. Journal of Food Science, 71(8), 495-498. http://dx.doi.org/10.1111/j.1750-3841.2006.00147.x.
http://dx.doi.org/10.1111/j.1750-3841.20...
. However, flaxseed protein at pH 6 exhibited the foaming capacity with low volume, but a high stability. In the study of Mueller et al. (2010)Mueller, K., Eisner, P., Yoshie-Stark, Y., Nakada, R., & Kirchhoff, E. (2010). Functional properties and chemical composition of fractionated brown and yellow linseed meal (Linum usitatissimum L.). Journal of Food Engineering, 98(4), 453-460. http://dx.doi.org/10.1016/j.jfoodeng.2010.01.028.
http://dx.doi.org/10.1016/j.jfoodeng.201...
, acid-soluble flaxseed protein with poor foaming capacity was also indicated. Lan et al. (2020)Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731.
http://dx.doi.org/10.1016/j.foodhyd.2020...
reported that flaxseed protein isolates showed significantly higher foaming capacity compared to flaxseed protein concentrates at investigated pHs.

5 Preparation of flaxseed protein hydrolysates for health benefits

More evidence have showed that flaxseed protein can provide us health benefits (Akbarbaglu et al., 2019Akbarbaglu, Z., Jafari, S. M., Sarabandi, K., Mohammadi, M., Heshmati, M. K., & Pezeshki, A. (2019). Influence of spray drying encapsulation on the retention of antioxidant properties and microstructure of flaxseed protein hydrolystates. Colloids and Surfaces. B, Biointerfaces, 178, 421-429. http://dx.doi.org/10.1016/j.colsurfb.2019.03.038. PMid:30908998.
http://dx.doi.org/10.1016/j.colsurfb.201...
; Marie et al., 2019Marie, G. C. U., Perreault, V., Henaux, L., Carnovale, V., Aluko, R. E., Marette, A., Doyen, A., & Bazinet, L. (2019). Impact of a high hydrostatic pressure pretreatment on the separation of bioactive peptides from flaxseed protein hydrolysates by electrodialysis with ultrafiltration membranes. Separation and Purification Technology, 211, 242-251. http://dx.doi.org/10.1016/j.seppur.2018.09.063.
http://dx.doi.org/10.1016/j.seppur.2018....
; Nwachukwu & Aluko, 2018aNwachukwu, I. D., & Aluko, R. E. (2018a). Antioxidant properties of flaxseed protein hydrolysates: influence of hydrolytic enzyme concentration and peptide size. Journal of the American Oil Chemists’ Society, 95(8), 1105-1118. http://dx.doi.org/10.1002/aocs.12042.
http://dx.doi.org/10.1002/aocs.12042...
; Udenigwe et al., 2009Udenigwe, C. C., Lin, Y. S., Hou, W. C., & Aluko, R. E. (2009). Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions. Journal of Functional Foods, 1(2), 199-207. http://dx.doi.org/10.1016/j.jff.2009.01.009.
http://dx.doi.org/10.1016/j.jff.2009.01....
; Wei et al., 2018Wei, C. K., Thakur, K., Liu, D. H., Zhang, J. G., & Wei, Z. J. (2018). Enzymatic hydrolysis of flaxseed (Linum usitatissimum L.) protein and sensory characterization of Maillard reaction products. Food Chemistry, 263, 186-193. http://dx.doi.org/10.1016/j.foodchem.2018.04.120. PMid:29784306.
http://dx.doi.org/10.1016/j.foodchem.201...
; Yu et al., 2020Yu, X., Huang, S., Nie, C., Deng, Q., Zhai, Y., & Shen, R. (2020). Effects of atmospheric pressure plasma jet on the physicochemical, functional, and antioxidant properties of flaxseed protein. Journal of Food Science, 85(7), 2010-2019. http://dx.doi.org/10.1111/1750-3841.15184. PMid:32529640.
http://dx.doi.org/10.1111/1750-3841.1518...
). Health benefits of flaxseed protein, such as anti-cholesterol, antioxidant, anti-tumour properties, anti-hyperglycemia, are attributed to the amino acid composition, the interaction with other compounds such as ALA, mucilage or phenolic compounds (Langyan et al., 2021Langyan, S., Khan, F. N., Yadava, P., Alhazmi, A., Mahmoud, S. F., Saleh, D. I., Zuan, A. T. K., & Kumar, A. (2021). In silico proteolysis and analysis of bioactive peptides from sequences of fatty acid desaturase 3 (FAD3) of flaxseed protein. Saudi Journal of Biological Sciences, 28(10), 5480-5489. http://dx.doi.org/10.1016/j.sjbs.2021.08.027. PMid:34588858.
http://dx.doi.org/10.1016/j.sjbs.2021.08...
; Rabetafika et al., 2011Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x.
http://dx.doi.org/10.1111/j.1365-2621.20...
). Mohamed et al. (2020)Mohamed, R. S., Fouda, K., & Akl, E. M. (2020). Hepatorenal protective effect of flaxseed protein isolate incorporated in lemon juice against lead toxicity in rats. Toxicology Reports, 7, 30-35. http://dx.doi.org/10.1016/j.toxrep.2019.12.001. PMid:31890606.
http://dx.doi.org/10.1016/j.toxrep.2019....
found that flaxseed protein isolates had high antioxidant activity when flaxseed protein isolates was solubilized in lemon juice (pH = 2-3). The lemon juice containing flaxseed protein isolates showed hepatorenal protective activity against lead on liver and kidney in rats. The health activities of flaxseed protein can be increased further through enzymatic hydrolysis (Silva et al., 2017Silva, F. G. D., Hernandez-Ledesma, B., Amigo, L., Netto, F. M., & Miralles, B. (2017). Identification of peptides released from flaxseed (Linum usitatissimum) protein by Alclase hydrolysis: antioxidant activity. Lebensmittel-Wissenschaft + Technologie, 76, 140-146. http://dx.doi.org/10.1016/j.lwt.2016.10.049.
http://dx.doi.org/10.1016/j.lwt.2016.10....
; Teh et al., 2016Teh, S. S., Bekhit, A. E. A., Carne, A., & Birch, J. (2016). Antioxidant and ACE-inhibitory activities of hemp (Cannabis sativa L.) protein hydrolysates produced by the proteases AFP, HT, Pro-G, actinidin and zingibain. Food Chemistry, 203, 199-206. http://dx.doi.org/10.1016/j.foodchem.2016.02.057. PMid:26948606.
http://dx.doi.org/10.1016/j.foodchem.201...
). These hydrolysates have been attracted increasing attention, which provide beneficial activities to our health. Many health benefits of flaxseed protein hydrolysates, such as anti-hypertension ability, antibacterial activity, antioxidant capacity, anti-diabetic ability, and the inhibition ability of calmodulin-dependent neuronal nitric oxide synthase, have been reported (Franck et al., 2019Franck, M., Perreault, V., Suwal, S., Marciniak, A., Bazinet, L., & Doyen, A. (2019). High hydrostatic pressure-assisted enzymatic hydrolysis improved protein digestion of flaxseed protein isolate and generation of peptides with antioxidant activity. Food Research International, 115, 467-473. http://dx.doi.org/10.1016/j.foodres.2018.10.034. PMid:30599966.
http://dx.doi.org/10.1016/j.foodres.2018...
; Logarušić et al., 2020Logarušić, M., Radošević, K., Bis, A., Panić, M., Slivac, I., & Srček, V. G. (2020). Biological potential of flaxseed protein hydrolysates obtained by different proteases. Plant Foods for Human Nutrition, 75(4), 518-524. http://dx.doi.org/10.1007/s11130-020-00841-z. PMid:32766942.
http://dx.doi.org/10.1007/s11130-020-008...
; Nwachukwu & Aluko, 2018aNwachukwu, I. D., & Aluko, R. E. (2018a). Antioxidant properties of flaxseed protein hydrolysates: influence of hydrolytic enzyme concentration and peptide size. Journal of the American Oil Chemists’ Society, 95(8), 1105-1118. http://dx.doi.org/10.1002/aocs.12042.
http://dx.doi.org/10.1002/aocs.12042...
, bNwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
; Perreault et al., 2017Perreault, V., Henaux, L., Bazinet, L., & Doyen, A. (2017). Pretreatment of flaxseed protein isolate by high hydrostatic pressure: impacts on protein structure, enzymatic hydrolysis and final hydrolysate antioxidant capacities. Food Chemistry, 221, 1805-1812. http://dx.doi.org/10.1016/j.foodchem.2016.10.100. PMid:27979166.
http://dx.doi.org/10.1016/j.foodchem.201...
; Silva et al., 2017Silva, F. G. D., Hernandez-Ledesma, B., Amigo, L., Netto, F. M., & Miralles, B. (2017). Identification of peptides released from flaxseed (Linum usitatissimum) protein by Alclase hydrolysis: antioxidant activity. Lebensmittel-Wissenschaft + Technologie, 76, 140-146. http://dx.doi.org/10.1016/j.lwt.2016.10.049.
http://dx.doi.org/10.1016/j.lwt.2016.10....
; Udenigwe & Aluko, 2010Udenigwe, C. C., & Aluko, R. E. (2010). Antioxidant and angiotensin converting enzyme-inhibitory properties of a flaxseed protein-derived high fischer ratio peptide mixture. Journal of Agricultural and Food Chemistry, 58(8), 4762-4768. http://dx.doi.org/10.1021/jf100149w. PMid:20218606.
http://dx.doi.org/10.1021/jf100149w...
, 2012Udenigwe, C. C., & Aluko, R. E. (2012). Multifunctional cationic peptide fractions from flaxseed protein hydrolysates. Plant Foods for Human Nutrition (Dordrecht, Netherlands), 67(1), 1-9. http://dx.doi.org/10.1007/s11130-012-0275-3. PMid:22327315.
http://dx.doi.org/10.1007/s11130-012-027...
; Wu et al., 2019Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017.
http://dx.doi.org/10.1016/j.tifs.2019.08...
).

5.1 Pre-treatment of flaxseed protein

Many food-grade hydrolytic enzymes, including trypsin, Flavourzyme®, alcalase, thermolysin, pronase, pepsin, ficin, papain, pancreatin, Thermoase®, and protease from Bacillus altitudinis, have been employed to produce flaxseed protein hydrolysates using controlled or limited hydrolysis technology (Hwang et al., 2016Hwang, C. F., Chen, Y. A., Luo, C., & Chiang, W. D. (2016). Antioxidant and antibacterial activities of peptide fractions from flaxseed protein hydrolysed by protease from Bacillus altitudinis HK02. International Journal of Food Science & Technology, 51(3), 681-689. http://dx.doi.org/10.1111/ijfs.13030.
http://dx.doi.org/10.1111/ijfs.13030...
; Karamać et al., 2016Karamać, M., Kosińskacagnazzo, A., & Kulczyk, A. (2016). Use of different proteases to obtain flaxseed protein hydrolysates with antioxidant activity. International Journal of Molecular Sciences, 17(7), 1027-1039. http://dx.doi.org/10.3390/ijms17071027. PMid:27367678.
http://dx.doi.org/10.3390/ijms17071027...
; Marambe et al., 2008Marambe, P. W. M. L. H. K., Shand, P. J., & Wanasundara, J. P. D. (2008). An in vitro investigation of selected biological activities of hydrolyzed flaxseed (Linum usitatissimum L.) proteins. Journal of the American Oil Chemists’ Society, 85(12), 1155-1164. http://dx.doi.org/10.1007/s11746-008-1293-z.
http://dx.doi.org/10.1007/s11746-008-129...
, 2011Marambe, H. K., Shand, P. J., & Wanasundara, J. P. D. (2011). Release of angiotensin I-converting enzyme inhibitory peptides from flaxseed (Linum usitatissimum L.) protein under simulated gastrointestinal digestion. Journal of Agricultural and Food Chemistry, 59(17), 9596-9604. http://dx.doi.org/10.1021/jf202000e. PMid:21776963.
http://dx.doi.org/10.1021/jf202000e...
; Nwachukwu & Aluko, 2018aNwachukwu, I. D., & Aluko, R. E. (2018a). Antioxidant properties of flaxseed protein hydrolysates: influence of hydrolytic enzyme concentration and peptide size. Journal of the American Oil Chemists’ Society, 95(8), 1105-1118. http://dx.doi.org/10.1002/aocs.12042.
http://dx.doi.org/10.1002/aocs.12042...
, bNwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
; Perreault et al., 2017Perreault, V., Henaux, L., Bazinet, L., & Doyen, A. (2017). Pretreatment of flaxseed protein isolate by high hydrostatic pressure: impacts on protein structure, enzymatic hydrolysis and final hydrolysate antioxidant capacities. Food Chemistry, 221, 1805-1812. http://dx.doi.org/10.1016/j.foodchem.2016.10.100. PMid:27979166.
http://dx.doi.org/10.1016/j.foodchem.201...
; Sarabandi & Jafari, 2020aSarabandi, K., & Jafari, S. M. (2020a). Fractionation of flaxseed-derived bioactive peptides and their influence on nanoliposomal carriers. Journal of Agricultural and Food Chemistry, 68(51), 15097-15106. http://dx.doi.org/10.1021/acs.jafc.0c02583. PMid:33290068.
http://dx.doi.org/10.1021/acs.jafc.0c025...
, bSarabandi, K., & Jafari, S. M. (2020b). Improving the antioxidant stability of flaxseed peptide fractions during spray drying encapsulation by surfactants: physicochemical and morphological features. Journal of Food Engineering, 286, 110131. http://dx.doi.org/10.1016/j.jfoodeng.2020.110131.
http://dx.doi.org/10.1016/j.jfoodeng.202...
; Udenigwe et al., 2012Udenigwe, C. C., Adebiyi, A. P., Doyen, A., Li, H., Bazinet, L., & Aluko, R. E. (2012). Low molecular weight flaxseed protein-derived arginine-containing peptides reduced blood pressure of spontaneously hypertensive rats faster than amino acid form of arginine and native flaxseed protein. Food Chemistry, 132(1), 468-475. http://dx.doi.org/10.1016/j.foodchem.2011.11.024. PMid:26434317.
http://dx.doi.org/10.1016/j.foodchem.201...
; Udenigwe & Aluko, 2010Udenigwe, C. C., & Aluko, R. E. (2010). Antioxidant and angiotensin converting enzyme-inhibitory properties of a flaxseed protein-derived high fischer ratio peptide mixture. Journal of Agricultural and Food Chemistry, 58(8), 4762-4768. http://dx.doi.org/10.1021/jf100149w. PMid:20218606.
http://dx.doi.org/10.1021/jf100149w...
; Wu et al., 2019Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017.
http://dx.doi.org/10.1016/j.tifs.2019.08...
). The digestibility of flaxseed protein is very important factor to affect the preparation of the hydrolysates. Many factors, for instance flaxseed ingredients (especially the mucilage and flaxseed oil), the pre-treatment methods, can significantly affect the digestibility of flaxseed protein. Thus, the pretreatment of raw material is assumed to be an important step for producing the hydrolysates (Franck et al., 2019Franck, M., Perreault, V., Suwal, S., Marciniak, A., Bazinet, L., & Doyen, A. (2019). High hydrostatic pressure-assisted enzymatic hydrolysis improved protein digestion of flaxseed protein isolate and generation of peptides with antioxidant activity. Food Research International, 115, 467-473. http://dx.doi.org/10.1016/j.foodres.2018.10.034. PMid:30599966.
http://dx.doi.org/10.1016/j.foodres.2018...
; Marie et al., 2019Marie, G. C. U., Perreault, V., Henaux, L., Carnovale, V., Aluko, R. E., Marette, A., Doyen, A., & Bazinet, L. (2019). Impact of a high hydrostatic pressure pretreatment on the separation of bioactive peptides from flaxseed protein hydrolysates by electrodialysis with ultrafiltration membranes. Separation and Purification Technology, 211, 242-251. http://dx.doi.org/10.1016/j.seppur.2018.09.063.
http://dx.doi.org/10.1016/j.seppur.2018....
; Perreault et al., 2017Perreault, V., Henaux, L., Bazinet, L., & Doyen, A. (2017). Pretreatment of flaxseed protein isolate by high hydrostatic pressure: impacts on protein structure, enzymatic hydrolysis and final hydrolysate antioxidant capacities. Food Chemistry, 221, 1805-1812. http://dx.doi.org/10.1016/j.foodchem.2016.10.100. PMid:27979166.
http://dx.doi.org/10.1016/j.foodchem.201...
). The mucilage and oils in flaxseed can prevent the digestive enzymes from hydrolyzing flaxseed protein, and thus lead to the decrease of flaxseed protein digestibility. Therefore, the digestibility of flaxseed protein can be improved after the mucilage and oil in flaxseed are removed. Marambe et al. (2013)Marambe, H. K., Shand, P. J., & Wanasundara, J. P. D. (2013). In vitro digestibility of flaxseed (Linum usitatissimum L.) protein: effect of seed mucilage, oil and thermal processing. International Journal of Food Science & Technology, 48(3), 628-635. http://dx.doi.org/10.1111/ijfs.12008.
http://dx.doi.org/10.1111/ijfs.12008...
reported the protein digestibility in flaxseed meal could reach 66.8% after the mucilage and oil were removed, compared to 12.6% for ground flaxseed with the mucilage and full-fat. Perreault et al. (2017)Perreault, V., Henaux, L., Bazinet, L., & Doyen, A. (2017). Pretreatment of flaxseed protein isolate by high hydrostatic pressure: impacts on protein structure, enzymatic hydrolysis and final hydrolysate antioxidant capacities. Food Chemistry, 221, 1805-1812. http://dx.doi.org/10.1016/j.foodchem.2016.10.100. PMid:27979166.
http://dx.doi.org/10.1016/j.foodchem.201...
improved the digestibility of flaxseed protein by high hydrostatic pressure technology, and also found antioxidant activity of protein hydrolysates was enhanced. Heating treatment such as home-style baking, boiling and extrusion process, also can improve the digestibility of flaxseed protein, which is due to the structural changes of flaxseed protein (Khan et al., 2015Khan, N. A., Booker, H., & Yu, P. (2015). Effect of heating method on alteration of protein molecular structure in flaxseed: Relationship with changes in protein subfraction profile and digestion in dairy cows. Journal of Agricultural and Food Chemistry, 63(4), 1057-1066. http://dx.doi.org/10.1021/jf503575y. PMid:25578477.
http://dx.doi.org/10.1021/jf503575y...
; Wang et al., 2008Wang, Y., Li, D., Wang, L. J., Chiu, Y. L., Chen, X. D., Mao, Z. H., & Song, C. F. (2008). Optimization of extrusion of flaxseeds for in vitro protein digestibility analysis using response surface methodology. Journal of Food Engineering, 85(1), 59-64. http://dx.doi.org/10.1016/j.jfoodeng.2007.06.033.
http://dx.doi.org/10.1016/j.jfoodeng.200...
). Khan et al. (2015)Khan, N. A., Booker, H., & Yu, P. (2015). Effect of heating method on alteration of protein molecular structure in flaxseed: Relationship with changes in protein subfraction profile and digestion in dairy cows. Journal of Agricultural and Food Chemistry, 63(4), 1057-1066. http://dx.doi.org/10.1021/jf503575y. PMid:25578477.
http://dx.doi.org/10.1021/jf503575y...
found that flaxseed protein solubility decreased from 56.5 to 25.9% after flaxseed protein was treated by moist heating processing, and led to the increase of the protein digestibility. Through the pre-treatment investigations for flaxseed protein, flaxseed protein hydrolysates showed better functional and nutraceutical values compared to untreated flaxseed protein.

5.2 Anti-hypertensive capacity

The most extensive studies may be the anti-hypertensive activity among all the activities of flaxseed protein hydrolysates. Many flaxseed protein hydrolysates are prepared using single enzyme, complex enzyme preparation or enzyme combination, which can inhibit the angiotensin I-converting enzyme or renin activity (Marambe et al., 2008Marambe, P. W. M. L. H. K., Shand, P. J., & Wanasundara, J. P. D. (2008). An in vitro investigation of selected biological activities of hydrolyzed flaxseed (Linum usitatissimum L.) proteins. Journal of the American Oil Chemists’ Society, 85(12), 1155-1164. http://dx.doi.org/10.1007/s11746-008-1293-z.
http://dx.doi.org/10.1007/s11746-008-129...
; Nwachukwu et al., 2014Nwachukwu, I. D., Girgih, A. T., Malomo, S. A., Onuh, J. O., & Aluko, R. E. (2014). Thermoase-derived flaxseed protein hydrolysates and membrane ultrafiltration peptide fractions have systolic blood pressure-lowering effects in spontaneously hypertensive rats. International Journal of Molecular Sciences, 15(10), 18131-18147. http://dx.doi.org/10.3390/ijms151018131. PMid:25302619.
http://dx.doi.org/10.3390/ijms151018131...
). Wu et al. (2009)Wu, J.P., Muir, A.D., & Aluko, R.E. (2009). AEC inhibitory peptides from plant materials. Patent No. US007566690B2. obtained the hydrolysates from DFM by the use of alcalase, thermolysin or the combination of both enzymes. The half-maximal inhibitory concentration (IC50) value of the hydrolysates generated by a combination of alcalase and thermolysin was 34.2 μg/mL, while IC50 value of the hydrolysates through alcalase, thermolysin, were 64.3, 37.1 μg/mL, respectively. The authors indicated the hydrolysates obtained by a combination of alcalase and thermolysin showed better anti-hypertensive ability than those obtained by single enzyme.

Arginine-rich hydrolysates obtained from flaxseed protein showed a potential anti-hypertensive ability (Wu et al., 2019Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017.
http://dx.doi.org/10.1016/j.tifs.2019.08...
). Udenigwe et al. (2009)Udenigwe, C. C., Lin, Y. S., Hou, W. C., & Aluko, R. E. (2009). Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions. Journal of Functional Foods, 1(2), 199-207. http://dx.doi.org/10.1016/j.jff.2009.01.009.
http://dx.doi.org/10.1016/j.jff.2009.01....
employed several proteases, such as pepsin, alcalase, trypsin, ficin, thermolysin, or pancreatin hydrolysis, to prepare flaxseed protein hydrolysates. The authors indicated IC50 values of the hydrolysates changed from 1.22 to 2.81 mg/mL. The obtained cationic peptide fraction of alcalase-hydrolysates exhibited the highest activity. The same group (Udenigwe & Aluko, 2010Udenigwe, C. C., & Aluko, R. E. (2010). Antioxidant and angiotensin converting enzyme-inhibitory properties of a flaxseed protein-derived high fischer ratio peptide mixture. Journal of Agricultural and Food Chemistry, 58(8), 4762-4768. http://dx.doi.org/10.1021/jf100149w. PMid:20218606.
http://dx.doi.org/10.1021/jf100149w...
) produced flaxseed protein hydrolysates by thermolysin and pronase, and evaluated the activity of flaxseed protein hydrolysates in spontaneously hypertensive rates. The results manifested that the cationic fraction of the hydrolysates possessed lower systolic blood pressure ability than flaxseed protein isolates. Flaxseed protein isolates could decrease blood pressure effectively within 4 h after feeding flaxseed protein hydrolysates, however the cationic hydrolysates only needed 2 h to reach the similar levels.

Marambe et al. (2011)Marambe, H. K., Shand, P. J., & Wanasundara, J. P. D. (2011). Release of angiotensin I-converting enzyme inhibitory peptides from flaxseed (Linum usitatissimum L.) protein under simulated gastrointestinal digestion. Journal of Agricultural and Food Chemistry, 59(17), 9596-9604. http://dx.doi.org/10.1021/jf202000e. PMid:21776963.
http://dx.doi.org/10.1021/jf202000e...
obtained the hydrolysates using the combination of pepsin-pancreatin under the simulated gastrointestinal digestion. The results indicated that anti-hypertensive activity of the hydrolysates obtained by pepsin-pancreatin was higher than that of pepsin-produced hydrolysates. In addition, the hydrolysis degree (43.95%) obtained in dynamic digestion was higher than that from pepsin hydrolysis (7.96%). Pancreatin is a mixture of enzymes including apancreatic amylase protease, pancreatic lipase, which has no specificity for the sequence of amino acids (Marambe et al., 2011Marambe, H. K., Shand, P. J., & Wanasundara, J. P. D. (2011). Release of angiotensin I-converting enzyme inhibitory peptides from flaxseed (Linum usitatissimum L.) protein under simulated gastrointestinal digestion. Journal of Agricultural and Food Chemistry, 59(17), 9596-9604. http://dx.doi.org/10.1021/jf202000e. PMid:21776963.
http://dx.doi.org/10.1021/jf202000e...
; Wu et al., 2019Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017.
http://dx.doi.org/10.1016/j.tifs.2019.08...
). So, the higher hydrolysis degree and smaller hydrolysates were easy to be obtained after flaxseed protein was treated by pancreatin (Karamać et al., 2016Karamać, M., Kosińskacagnazzo, A., & Kulczyk, A. (2016). Use of different proteases to obtain flaxseed protein hydrolysates with antioxidant activity. International Journal of Molecular Sciences, 17(7), 1027-1039. http://dx.doi.org/10.3390/ijms17071027. PMid:27367678.
http://dx.doi.org/10.3390/ijms17071027...
). Additionally, Udenigwe et al. (2012)Udenigwe, C. C., Adebiyi, A. P., Doyen, A., Li, H., Bazinet, L., & Aluko, R. E. (2012). Low molecular weight flaxseed protein-derived arginine-containing peptides reduced blood pressure of spontaneously hypertensive rats faster than amino acid form of arginine and native flaxseed protein. Food Chemistry, 132(1), 468-475. http://dx.doi.org/10.1016/j.foodchem.2011.11.024. PMid:26434317.
http://dx.doi.org/10.1016/j.foodchem.201...
employed the combination of pronase and trypsin to prepare the hydrolysates with anti-hypertensive activity. The obtained arginine-rich hydrolysates presented moderate anti-hypertensive and renin-inhibitory effects. Trypsin could specifically hydrolyze peptide bonds between carboxylic acid group of lysine or argnine, and thus the hydrolyasates with arginine residues were generally generated (Udenigwe et al., 2012Udenigwe, C. C., Adebiyi, A. P., Doyen, A., Li, H., Bazinet, L., & Aluko, R. E. (2012). Low molecular weight flaxseed protein-derived arginine-containing peptides reduced blood pressure of spontaneously hypertensive rats faster than amino acid form of arginine and native flaxseed protein. Food Chemistry, 132(1), 468-475. http://dx.doi.org/10.1016/j.foodchem.2011.11.024. PMid:26434317.
http://dx.doi.org/10.1016/j.foodchem.201...
; Wu et al., 2019Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017.
http://dx.doi.org/10.1016/j.tifs.2019.08...
).

In order to improve enzymatic hydrolysis efficiency and the recovery of flaxseed protein hydrolysates, Marie et al. (2019)Marie, G. C. U., Perreault, V., Henaux, L., Carnovale, V., Aluko, R. E., Marette, A., Doyen, A., & Bazinet, L. (2019). Impact of a high hydrostatic pressure pretreatment on the separation of bioactive peptides from flaxseed protein hydrolysates by electrodialysis with ultrafiltration membranes. Separation and Purification Technology, 211, 242-251. http://dx.doi.org/10.1016/j.seppur.2018.09.063.
http://dx.doi.org/10.1016/j.seppur.2018....
used the combination of high hydrostatic pressure and electrodialysis with ultrafiltration membranes to produce flaxseed protein hydrolysates. The results indicated that the hydrolysates in KCl fraction were rich in arginine, and could decrease blood pressure in rats with spontaneously hypertension.

5.3 Antioxidant capacity

The antioxidant ability of flaxseed protein hydrolysates highly depends on many factors, such as molecular weight of the hydrolysates, amino acid composition, the types of enzyme, pre-treatment methods for flaxseed protein (Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Nwachukwu & Aluko, 2018aNwachukwu, I. D., & Aluko, R. E. (2018a). Antioxidant properties of flaxseed protein hydrolysates: influence of hydrolytic enzyme concentration and peptide size. Journal of the American Oil Chemists’ Society, 95(8), 1105-1118. http://dx.doi.org/10.1002/aocs.12042.
http://dx.doi.org/10.1002/aocs.12042...
, bNwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068. PMid:29571469.
http://dx.doi.org/10.1016/j.foodchem.201...
; Udenigwe et al., 2009Udenigwe, C. C., Lin, Y. S., Hou, W. C., & Aluko, R. E. (2009). Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions. Journal of Functional Foods, 1(2), 199-207. http://dx.doi.org/10.1016/j.jff.2009.01.009.
http://dx.doi.org/10.1016/j.jff.2009.01....
). Logarušić et al. (2020)Logarušić, M., Radošević, K., Bis, A., Panić, M., Slivac, I., & Srček, V. G. (2020). Biological potential of flaxseed protein hydrolysates obtained by different proteases. Plant Foods for Human Nutrition, 75(4), 518-524. http://dx.doi.org/10.1007/s11130-020-00841-z. PMid:32766942.
http://dx.doi.org/10.1007/s11130-020-008...
investigated in vitro antioxidant abilities of flaxseed protein hydrolysates prepared by Alcalase, Neutrase and Protamex, respectively. The authors indicated that the obtained flaxseed protein hydrolysates from alcalase showed the strongest antioxidant ability, whereas those obtained by Neutrase and Protamex exhibited lower or no antioxidant ability at all. Udenigwe et al. (2009)Udenigwe, C. C., Lin, Y. S., Hou, W. C., & Aluko, R. E. (2009). Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions. Journal of Functional Foods, 1(2), 199-207. http://dx.doi.org/10.1016/j.jff.2009.01.009.
http://dx.doi.org/10.1016/j.jff.2009.01....
employed various proteases to produce flaxseed protein hydrolysates, and found that the hydrolysates generated by alcalase exhibited the highest DPPH· scavenging ability compared to other proteases hydrolysates. The reason for the difference was related to the specificity of proteases. In the same group, Udenigwe & Aluko (2010)Udenigwe, C. C., & Aluko, R. E. (2010). Antioxidant and angiotensin converting enzyme-inhibitory properties of a flaxseed protein-derived high fischer ratio peptide mixture. Journal of Agricultural and Food Chemistry, 58(8), 4762-4768. http://dx.doi.org/10.1021/jf100149w. PMid:20218606.
http://dx.doi.org/10.1021/jf100149w...
reported that the hydrolysates with a high-Fischer-ratio showed lower ·OH scavenging activity compared to those with low molecular weight hydrolysates. It might be attributed to the low phenylalanine content in the hydrolysates. However, the hydrolysates with high-Fischer-ratio showed higher O2· scavenging ability compared to the hydrolysates with low molecular weight. Similarly, Hwang et al. (2016)Hwang, C. F., Chen, Y. A., Luo, C., & Chiang, W. D. (2016). Antioxidant and antibacterial activities of peptide fractions from flaxseed protein hydrolysed by protease from Bacillus altitudinis HK02. International Journal of Food Science & Technology, 51(3), 681-689. http://dx.doi.org/10.1111/ijfs.13030.
http://dx.doi.org/10.1111/ijfs.13030...
reported that the hydrolysates with low molecular weight exhibited higher ABTS free radical-scavenging activity than high molecular weight hydrolysates, whereas the hydrolysates with high molecular weight presented the better reducing power ability compared to those of Vitamin E, Vitamin C, and BHA. Recently, Sarabandi & Jafari (2020a)Sarabandi, K., & Jafari, S. M. (2020a). Fractionation of flaxseed-derived bioactive peptides and their influence on nanoliposomal carriers. Journal of Agricultural and Food Chemistry, 68(51), 15097-15106. http://dx.doi.org/10.1021/acs.jafc.0c02583. PMid:33290068.
http://dx.doi.org/10.1021/acs.jafc.0c025...
also found the hydrolysis by Alcalase could significantly increase the release of antioxidant amino acids from DFM. The hydrolysates with low molecular weights (< 10 kDa) exhibited the highest scavenging capacities for DPPH- and ABTS+ free radicals.

Luna-Vital et al. (2015)Luna-Vital, D. A., Mojica, L., Mejía, E. G., Mendoza, S., & Loarca-Piña, G. (2015). Biological potential of protein hydrolysates and peptides from common bean (Phaseolus vulgaris L.): a review. Food Research International, 76, 39-50. http://dx.doi.org/10.1016/j.foodres.2014.11.024.
http://dx.doi.org/10.1016/j.foodres.2014...
reported that the excellent antioxidant ability of the hydrolysates was due to hydrophobic amino acids, such as glycine, phenylalanine, tryptophane, cysteine or alanine, in the N-terminus of the hydrolysates. Besides, in the study of Silva et al. (2017)Silva, F. G. D., Hernandez-Ledesma, B., Amigo, L., Netto, F. M., & Miralles, B. (2017). Identification of peptides released from flaxseed (Linum usitatissimum) protein by Alclase hydrolysis: antioxidant activity. Lebensmittel-Wissenschaft + Technologie, 76, 140-146. http://dx.doi.org/10.1016/j.lwt.2016.10.049.
http://dx.doi.org/10.1016/j.lwt.2016.10....
, flaxseed protein hydrolysates were obtained by the hydrolysis of alcalase, and showed notable antioxidant activity. The authors speculated that hydrophobic amino acids in the hydrolysates contributed to good antioxidant activity of the hydrolysates. Additionally, after flaxseed protein was treated by high hydrostatic pressure (HHP) before the hydrolysis, the antioxidant activity of the hydrolysates could be improved further. The reason was that the structure of flaxseed protein was destroyed by HHP treatment, and led to the more release of the antioxidant hydrolysates. Perreault et al. (2017)Perreault, V., Henaux, L., Bazinet, L., & Doyen, A. (2017). Pretreatment of flaxseed protein isolate by high hydrostatic pressure: impacts on protein structure, enzymatic hydrolysis and final hydrolysate antioxidant capacities. Food Chemistry, 221, 1805-1812. http://dx.doi.org/10.1016/j.foodchem.2016.10.100. PMid:27979166.
http://dx.doi.org/10.1016/j.foodchem.201...
reported that the hydrolysates from HHP-treated flaxseed protein after enzymatic hydrolysis showed a higher antioxidant capacity than non-pretreated hydrolysates. Franck et al. (2019)Franck, M., Perreault, V., Suwal, S., Marciniak, A., Bazinet, L., & Doyen, A. (2019). High hydrostatic pressure-assisted enzymatic hydrolysis improved protein digestion of flaxseed protein isolate and generation of peptides with antioxidant activity. Food Research International, 115, 467-473. http://dx.doi.org/10.1016/j.foodres.2018.10.034. PMid:30599966.
http://dx.doi.org/10.1016/j.foodres.2018...
carried out the hydrolysis of flaxseed protein by typsin under HHP, and indicated that the hydrolysis of flaxseed protein by typsin at 300 MPa for 5 and 10 min could improve the antioxidant activity of the hydrolysates by 39 and 55%, respectively, compared to untreated samples.

5.4 Other beneficial activities

Besides anti-hypertensive and antioxidant activities, many other beneficial activities of flaxseed protein hydrolysates including anti-inflammation activity, antibacterial activity, and anti-diabetic ability, have been investigated (Wu et al., 2019Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017.
http://dx.doi.org/10.1016/j.tifs.2019.08...
). The hydrolysates with low molecular weight generated by using proteases such as pepsin, ficin, and papain, could inhibit the production of lipopolysaccharide-induced NO in RAW 264.7 macrophages. It was indicated that the hydrolysates showed anti-inflammatory activity (Udenigwe et al., 2009Udenigwe, C. C., Lin, Y. S., Hou, W. C., & Aluko, R. E. (2009). Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions. Journal of Functional Foods, 1(2), 199-207. http://dx.doi.org/10.1016/j.jff.2009.01.009.
http://dx.doi.org/10.1016/j.jff.2009.01....
). Doyen et al. (2014)Doyen, A., Udenigwe, C. C., Mitchell, P. L., Marette, A., Aluko, R. E., & Bazinet, L. (2014). Anti-diabetic and antihypertensive activities of two flaxseed protein hydrolysate fractions revealed following their simultaneous separation by electrodialysis with ultrafiltration membranes. Food Chemistry, 145, 66-76. http://dx.doi.org/10.1016/j.foodchem.2013.07.108. PMid:24128450.
http://dx.doi.org/10.1016/j.foodchem.201...
obtained specific cationic hydrolysates from flaxseed protein, and found it had an anti-diabetic ability after being evaluated in L6 cells.

Hwang et al. (2016)Hwang, C. F., Chen, Y. A., Luo, C., & Chiang, W. D. (2016). Antioxidant and antibacterial activities of peptide fractions from flaxseed protein hydrolysed by protease from Bacillus altitudinis HK02. International Journal of Food Science & Technology, 51(3), 681-689. http://dx.doi.org/10.1111/ijfs.13030.
http://dx.doi.org/10.1111/ijfs.13030...
found that flaxseed protein hydrolysates with low molecular weight (< 1 kDa) obtained by protease, showed better antibacterial ability against E. coli BCRC11634 and P. aeruginosa BCRC10944 compared to other hydrolysates with different molecular weights. Xu et al. (2008aXu, Y., Hall, C. III, & Wolf-Hall, C. (2008a). Antifungal activity stability of flaxseed protein extract using response surface methodology. Journal of Food Science, 73(1), M9-M14. http://dx.doi.org/10.1111/j.1750-3841.2007.00576.x. PMid:18211360.
http://dx.doi.org/10.1111/j.1750-3841.20...
, bXu, Y., Hall, C. III, & Wolf-Hall, C. (2008b). Fungistatic activity of heat-treated flaxseed determined by response surface methodology. Journal of Food Science, 73(6), M250-M256. http://dx.doi.org/10.1111/j.1750-3841.2008.00806.x. PMid:19241553.
http://dx.doi.org/10.1111/j.1750-3841.20...
) reported that flaxseed protein had antifungal activities against Candida albicans, Alternaria solani, and Aspergillus flavus.

Flaxseed protein hydrolysates can inhibit nNOS activity, and exhibit calmodulin (CaM)-binding activity (Udenigwe & Aluko, 2012Udenigwe, C. C., & Aluko, R. E. (2012). Multifunctional cationic peptide fractions from flaxseed protein hydrolysates. Plant Foods for Human Nutrition (Dordrecht, Netherlands), 67(1), 1-9. http://dx.doi.org/10.1007/s11130-012-0275-3. PMid:22327315.
http://dx.doi.org/10.1007/s11130-012-027...
). Omoni & Aluko (2006aOmoni, A. O., & Aluko, R. E. (2006a). Effect of cationic flaxseed protein hydrolysate fractions on the in vitro structure and activity of calmodulin-dependent endothelial nitric oxide synthase. Molecular Nutrition & Food Research, 50(10), 958-966. http://dx.doi.org/10.1002/mnfr.200600041. PMid:16967519.
http://dx.doi.org/10.1002/mnfr.200600041...
, bOmoni, A. O., & Aluko, R. E. (2006b). Mechanism of the inhibition of calmodulin-dependent neuronal nitric oxide synthase by flaxseed protein hydrolysates. Journal of the American Oil Chemists’ Society, 83(4), 335-340. http://dx.doi.org/10.1007/s11746-006-1209-8.
http://dx.doi.org/10.1007/s11746-006-120...
) obtained flaxseed protein hydrolysates by the use of alcalase. The results showed that < 1 kDa peptide hydrolysates exhibited CaM-binding activity. Udenigwe & Aluko (2012)Udenigwe, C. C., & Aluko, R. E. (2012). Multifunctional cationic peptide fractions from flaxseed protein hydrolysates. Plant Foods for Human Nutrition (Dordrecht, Netherlands), 67(1), 1-9. http://dx.doi.org/10.1007/s11130-012-0275-3. PMid:22327315.
http://dx.doi.org/10.1007/s11130-012-027...
obtained cationic flaxseed protein hydrolysates with the inhibition of CaM dependent phosphodiesterase activity. It was indicated that cationic hydrolysates could potentially enhance its use in treating cardiovascular disease with many symptoms.

6 Potential applications of flaxseed protein in foods

At present, the potential applications of flaxseed protein in foods are relatively limited. Flaxseed protein concentrates (LINOPROT 55) and its applications in real food systems such as dairy products, pastries, and meat, have been studied by the Finnish company of Flaxseed protein Ltd (Rabetafika et al., 2011Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x.
http://dx.doi.org/10.1111/j.1365-2621.20...
). Glanbia Nutritionals is one of major manufacturers for flaxseed protein products ranging from the concentrates to protein blends (Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
). Some applications of flaxseed protein in foods are presented in Table 4 and 5 and Figure 1.

Table 4
Potential applications of flaxseed protein in foods.
Table 5
Commercially available flaxseed protein powder.
Figure 1
Flaxseed protein powders and flaxseed protein beverages. A: 70% content of protein; B: 85% content of protein; C: flaxseed protein instant powder; D: flax milk; E: flaxseed protein beverage.

Flaxseed proteins used as additives in many foods such as ice creams, meat emulsions, bakery products, sauces, have been studied (Table 4). Waszkowiak & Rudzinska (2014)Waszkowiak, K., & Rudzinska, M. (2014). Effect of flaxseed meal and extracts on lipid stability in a stored meat product. Journal of the American Oil Chemists’ Society, 91(6), 979-987. http://dx.doi.org/10.1007/s11746-014-2438-x. PMid:24882871.
http://dx.doi.org/10.1007/s11746-014-243...
determined effect of DFM on lipid oxidation in pork meatballs. The results showed that DFM could stabilize fatty acid composition in stored pork meatballs. Wang et al. (2010)Wang, B., Li, D., Wang, L., & Özkan, N. (2010). Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions. Journal of Food Engineering, 96(4), 555-561. http://dx.doi.org/10.1016/j.jfoodeng.2009.09.001.
http://dx.doi.org/10.1016/j.jfoodeng.200...
showed that flaxseed protein was a good ingredient to be used in meat and ice-cream products. It was attributed to good functionalities showed by flaxseed protein. Wei et al. (2018Wei, C. K., Thakur, K., Liu, D. H., Zhang, J. G., & Wei, Z. J. (2018). Enzymatic hydrolysis of flaxseed (Linum usitatissimum L.) protein and sensory characterization of Maillard reaction products. Food Chemistry, 263, 186-193. http://dx.doi.org/10.1016/j.foodchem.2018.04.120. PMid:29784306.
http://dx.doi.org/10.1016/j.foodchem.201...
, 2019Wei, C. K., Ni, Z. J., Thakur, K., Liao, A. M., Huang, J. H., & Wei, Z. J. (2019). Color and flavor of flaxseed protein hydrolysates Maillard reaction products: effect of cysteine, initial pH, and thermal treatment. International Journal of Food Properties, 22(1), 84-99. http://dx.doi.org/10.1080/10942912.2019.1573830.
http://dx.doi.org/10.1080/10942912.2019....
) investigated the enzymolysis process for producing flaxseed protein hydrolysates with different flavor characteristics. The results showed that flaxseed protein hydrolysates with molecular weight of 128-1000 Da contributed to meat-like flavor. It was indicated that flaxseed protein hydrolysates showed a potential application in food industry as flavor enhancers.

A partial replacement of wheat flour with flaxseed protein powder can improve the nutritional value of flour-based foods (Giacomino et al., 2013Giacomino, S., Peñas, E., Ferreyra, V., Pellegrino, N., Fournier, M., Apro, N., Carrión, M. O., & Frias, J. (2013). Extruded flaxseed meal enhances the nutritional quality of cereal-based products. Plant Foods for Human Nutrition (Dordrecht, Netherlands), 68(2), 131-136. http://dx.doi.org/10.1007/s11130-013-0359-8. PMid:23640296.
http://dx.doi.org/10.1007/s11130-013-035...
). The mucilage in flaxseed meal or flaxseed protein samples can significantly affect the characteristics of the foods (Gambuś et al., 2009Gambuś, H., Gambuś, F., Pastuszka, D., Wrona, P., Ziobro, R., Sabat, R., Mickowska, B., Nowotna, A., & Sikora, M. (2009). Quality of gluten-free supplemented cakes and biscuits. International Journal of Food Sciences and Nutrition, 60(Suppl. 4), 31-50. http://dx.doi.org/10.1080/09637480802375523. PMid:19330630.
http://dx.doi.org/10.1080/09637480802375...
; Marambe & Wanasundara, 2017Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1.
http://dx.doi.org/10.1016/B978-0-12-8027...
; Rabetafika et al., 2011Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x.
http://dx.doi.org/10.1111/j.1365-2621.20...
). Shearer & Davies (2005)Shearer, A. E. H., & Davies, C. G. A. (2005). Physicochemical properties of freshly baked and stored whole-wheat muffins with and without flaxseed meal. Journal of Food Quality, 28(2), 137-153. http://dx.doi.org/10.1111/j.1745-4557.2005.00004.x.
http://dx.doi.org/10.1111/j.1745-4557.20...
found that wheat flour substituted about 10-20% by flaxseed meal did not influence the texture and swelling of the foods during cooking process. In the study of Manthey et al. (2008)Manthey, F., Sinha, S., Wolf-Hall, C., & Hall, C. III (2008). Effect of flaxseed flour and packaging on shelf life of refrigerated pasta. Journal of Food Processing and Preservation, 32(1), 75-87. http://dx.doi.org/10.1111/j.1745-4549.2007.00166.x.
http://dx.doi.org/10.1111/j.1745-4549.20...
, the firmness of fresh pasta and macaroni incorporated 15% flaxseed meal was reduced due to the mucilage in flaxseed meal, but, the addition of flaxseed meal could prolong the shelf-life of the foods due to the antifungal ability of flaxseed protein. Wu et al. (2009)Wu, J.P., Muir, A.D., & Aluko, R.E. (2009). AEC inhibitory peptides from plant materials. Patent No. US007566690B2. also showed that the incorporation of flaxseed meal could improve the viscoelasticity of extruded pastes because of the interaction of starch, the mucilage, and protein. Bhise et al. (2015)Bhise, S., Kaur, A., & Aggarwal, P. (2015). Development of protein enriched noodles using texturized defatted meal from sunflower, flaxseed and soybean. Journal of Food Science and Technology, 52(9), 5882-5889. http://dx.doi.org/10.1007/s13197-014-1630-1. PMid:26345004.
http://dx.doi.org/10.1007/s13197-014-163...
developed the noodles using texturized defatted meal from flaxseed, sunflower, and soybean. The results of acceptability tests showed that the noodles with 10% texturized defatted meal of flaxseed and sunflower exhibited the highest overall scores. Drozlowska et al. (2020)Drozlowska, E., Lopusiewicz, L., Mezynska, M., & Bartkowiak, A. (2020). The effect of native and denaturated flaxseed meal extract on physiochemical properties of low fat mayonnaises. Journal of Food Measurement and Characterization, 14(2), 1135-1145. http://dx.doi.org/10.1007/s11694-019-00363-6.
http://dx.doi.org/10.1007/s11694-019-003...
investigated the effect of flaxseed meal extract on physiochemical properties of low fat mayonnaises. The oil phase was partially replaced by 5%, 10%, 15% of flaxseed meal extract. The results showed that the replacement could improve the stability of mayonnaise, indicating that flaxseed meal extract could be used as a fat replacer to manufacture mayonnaises with low fat content and healthy flaxseed protein.

Flaxseed meal is rich in flaxseed protein, which has also been investigated for the applications in the baking field (Table 4; Ganorkar et al., 2016Ganorkar, P. M., Patel, J. M., Shah, V., & Rangrej, V. V. (2016). Defatted flaxseed meal incorporated corn-rice flour blend based extruded product by response surface methodology. Journal of Food Science and Technology, 53(4), 1867-1877. http://dx.doi.org/10.1007/s13197-015-2134-3. PMid:27413213.
http://dx.doi.org/10.1007/s13197-015-213...
; Rodrigues et al., 2012Rodrigues, R. T., Fanaro, G. B., Duarte, R. C., Koike, A. C., & Villavicencio, A. L. C. H. (2012). A sensory evaluation of irradiated cookies made from flaxseed meal. Radiation Physics and Chemistry, 81(8), 1157-1159. http://dx.doi.org/10.1016/j.radphyschem.2012.02.001.
http://dx.doi.org/10.1016/j.radphyschem....
). Lipilina & Ganji (2009)Lipilina, E., & Ganji, V. (2009). Incorporation of ground flaxseed into bakery products and its effect on sensory and nutritional characteristics: a pilot study. Journal of Food Service, 20(1), 52-59. http://dx.doi.org/10.1111/j.1748-0159.2008.00124.x.
http://dx.doi.org/10.1111/j.1748-0159.20...
studied the applications of flaxseed meal in breads and muffins. The results showed that incorporation 30% and 50% of flaxseed meal into breads and muffins, respectively, could form the crust with a dark colour due to Maillard reaction between the mucilage and protein. According to Pohjanheimo et al. (2006)Pohjanheimo, T. A., Hakala, M. A., Tahvonen, R. L., Salminen, S. J., & Kallio, H. P. (2006). Flaxseed in bread making: effects on sensory quality, aging, and composition of bakery products. Journal of Food Science, 71(4), 343-348. http://dx.doi.org/10.1111/j.1750-3841.2006.00005.x.
http://dx.doi.org/10.1111/j.1750-3841.20...
, the breads made using flaxseed meal flour had lower firmness and higher moisture holding ability compared to flaxseed-free breads. The breads with high concentration of flaxseed meal had a lower crispness. The mucilage in flaxseed meal may be attributed to these characteristics (Lipilina & Ganji, 2009Lipilina, E., & Ganji, V. (2009). Incorporation of ground flaxseed into bakery products and its effect on sensory and nutritional characteristics: a pilot study. Journal of Food Service, 20(1), 52-59. http://dx.doi.org/10.1111/j.1748-0159.2008.00124.x.
http://dx.doi.org/10.1111/j.1748-0159.20...
; Rabetafika et al., 2011Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x.
http://dx.doi.org/10.1111/j.1365-2621.20...
). The consumer acceptability is one of important key factors to flaxseed protein-based products. Some sensory evaluation indicated that the maximum of 25 and 10% incorporation in cookies and breads, respectively, was suggested (Alpaslan & Hayta, 2006Alpaslan, M., & Hayta, M. (2006). The effects of flaxseed, soy and corn flours on the textural and sensory properties of a bakery product. Journal of Food Quality, 29(6), 617-627. http://dx.doi.org/10.1111/j.1745-4557.2006.00099.x.
http://dx.doi.org/10.1111/j.1745-4557.20...
; Hussain et al., 2006Hussain, S., Anjum, F. M., Butt, M. S., Khan, M. I., & Asghar, A. (2006). Physical and sensoric attributes of flaxseed flour supplemented cookies. Turkish Journal of Biology, 30, 87-92.). Rodrigues et al. (2012)Rodrigues, R. T., Fanaro, G. B., Duarte, R. C., Koike, A. C., & Villavicencio, A. L. C. H. (2012). A sensory evaluation of irradiated cookies made from flaxseed meal. Radiation Physics and Chemistry, 81(8), 1157-1159. http://dx.doi.org/10.1016/j.radphyschem.2012.02.001.
http://dx.doi.org/10.1016/j.radphyschem....
performed a sensory evaluation of irradiated flaxseed cookies. The sensory results showed that there was not significantly different between irradiated flaxseed cookies and control cookies.

Many flaxseed-based products have been also developed in our group, some of which are commercialized (Tang et al., 2016aTang, Z. X., Liang, J. Y., & Bian, J. Z. (2016a). Coarse cereal biscuits containing alpha-linolenic acid and a preparation method thereof. CN 201610762274: A., bTang, Z. X., Liang, J. Y., & Bian, J. Z. (2016b). Flaxseed milk tablets and a preparation method thereof. CN 201610757720: A., cTang, Z. X., Liang, J. Y., & Bian, J. Z. (2016c). Flaxseed soft sweets and a preparation method thereof. CN 201610755288: A., dTang, Z. X., Liang, J. Y., & Bian, J. Z. (2016d). Nutritious coarse cereal energy bar and a making method thereof. CN 201610754178: A., 2017Tang, Z. X., Liang, J. Y., & Bian, J. Z. (2017). Flaxseed kernel protein beverage and a preparation method thereof. CN 201710047917: A.; Tang & Bian, 2018aTang, Z. X., & Bian, J. Z. (2018a). Flaxseed nutritional food for lowing blood lipid and a preparation method thereof. CN 201811366312:A., bTang, Z. X., & Bian, J. Z. (2018b). Flaxseed nutritional food for strengthening brain and a production method thereof. CN 201811367137: A., cTang, Z. X., & Bian, J. Z. (2018c). Flaxseed protein beverage and a preparation method thereof. CN 201811252507: A., dTang, Z. X., & Bian, J. Z. (2018d). Nourishment enriched in proteins and flaxseed oil and a preparation method thereof. CN 201811252511.7.; Tang, 2019aTang, Z. X. (2019a). Flaxseed fat-reducing yogurt nutrition bar and a preparation method thereof. CN 201910603833.X., bTang, Z. X. (2019b). Flaxseed yogurt for women and a making method thereof. CN 201910814791.). Recently, we developed liquid flaxseed drinks based dehulled flaxseed meal enriched with flaxseed protein and flaxseed oil (Tang & Bian, 2018cTang, Z. X., & Bian, J. Z. (2018c). Flaxseed protein beverage and a preparation method thereof. CN 201811252507: A., dTang, Z. X., & Bian, J. Z. (2018d). Nourishment enriched in proteins and flaxseed oil and a preparation method thereof. CN 201811252511.7.). As many other plant protein drinks, dehulled flaxeed is treated by milling and homogenizing in order to obtain stable flaxseed protein-enriched beverage. It has been marketed since 2018. The shelf life of the obtained flaxseed protein-enriched beverage can reach more than 10 months. We also have developed flaxseed yogurt using dehulled flaxseed as raw material. Dehulled milled flaxseed and milk are co-fermented by Streptococcus thermophilus and Lactobacillus bulgaricus. This type of flaxseed yogurt is very beneficial for menopause women (Tang, 2019aTang, Z. X. (2019a). Flaxseed fat-reducing yogurt nutrition bar and a preparation method thereof. CN 201910603833.X., bTang, Z. X. (2019b). Flaxseed yogurt for women and a making method thereof. CN 201910814791.).

7 Conclusion

As other oilseed proteins, flaxseed protein possesses many functional characteristics, for example water/oil adsorption ability, emulsifying ability, foaming ability and stability. Regarding flaxseed protein hydrolysates, it also can provide several health promoting benefits, particularly anti-hypertensive and antioxidant activities. Therefore, it shows a potential utilization value as a functional additive in food industry. Some applications of flaxseed protein in food systems such as the emulsification, meat analogs, wheat flour substitute, muffins, breads, and ice cream, have been investigated. However, the development of flaxseed protein is still facing many challenges. At present, the development of large-scale production for flaxseed protein is highly desired. More extensive research on flaxseed protein and its hydrolysates, such as the studies regarding the structure modification technologies, the mechanisms for their health benefits, should be carried out. As the pursuing for healthy foods, we sure that more flaxseed protein-based products will be available in the future.

Acknowledgements

This work was supported by Scientific Innovation Teams in Tourism College of Zhejiang (No. 2021TDDS03) and Research Foundation of Education Department of Zhejiang (No.Y202147210).

  • Practical Application: This review provides the extraction, functionalities of flaxseed protein, discussing the preparation of flaxseed protein hydrolysates, with the aim to improve the applications of flaxseed protein in food industry.

References

  • Akbarbaglu, Z., Jafari, S. M., Sarabandi, K., Mohammadi, M., Heshmati, M. K., & Pezeshki, A. (2019). Influence of spray drying encapsulation on the retention of antioxidant properties and microstructure of flaxseed protein hydrolystates. Colloids and Surfaces. B, Biointerfaces, 178, 421-429. http://dx.doi.org/10.1016/j.colsurfb.2019.03.038 PMid:30908998.
    » http://dx.doi.org/10.1016/j.colsurfb.2019.03.038
  • Alpaslan, M., & Hayta, M. (2006). The effects of flaxseed, soy and corn flours on the textural and sensory properties of a bakery product. Journal of Food Quality, 29(6), 617-627. http://dx.doi.org/10.1111/j.1745-4557.2006.00099.x
    » http://dx.doi.org/10.1111/j.1745-4557.2006.00099.x
  • Arntfield, S. D. (2018). Proteins from oil-producing plants. In Y. D. Rada (Ed.), Proteins in food processing (pp. 187-221). UK: Woodhead publications. http://dx.doi.org/10.1016/B978-0-08-100722-8.00008-5
    » http://dx.doi.org/10.1016/B978-0-08-100722-8.00008-5
  • Bakowska-Barczak, A., Larminat, M. A., & Kolodziejczyk, P. P. (2020). The application of flax and hempseed in food, nutraceutical and personal care products. In R. M. Kozlowski & M. M. Talarczyk (Eds.), Handbook of natural fibers (pp. 557-590). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-818782-1.00017-1
    » http://dx.doi.org/10.1016/B978-0-12-818782-1.00017-1
  • Bekhit, A. E. A., Shavandi, A., Jodjaja, T., Birch, J., Teh, S., Ahmed, I. A. M., Al-Juhaimi, F. Y., Saeedi, P., & Bekhit, A. A. (2018). Flaxseed: composition, deoxification, utilization, and opportunities. Biocatalysis and Agricultural Biotechnology, 13, 129-152. http://dx.doi.org/10.1016/j.bcab.2017.11.017
    » http://dx.doi.org/10.1016/j.bcab.2017.11.017
  • Bhise, S., Kaur, A., & Aggarwal, P. (2015). Development of protein enriched noodles using texturized defatted meal from sunflower, flaxseed and soybean. Journal of Food Science and Technology, 52(9), 5882-5889. http://dx.doi.org/10.1007/s13197-014-1630-1 PMid:26345004.
    » http://dx.doi.org/10.1007/s13197-014-1630-1
  • Chung, M. W. Y., Lei, B., & Li-Chan, E. C. Y. (2005). Isolation and structural characterization of the major protein fraction from NorMan flaxseed (Linum usitatissimum L.). Food Chemistry, 90(1-2), 271-279. http://dx.doi.org/10.1016/j.foodchem.2003.07.038
    » http://dx.doi.org/10.1016/j.foodchem.2003.07.038
  • Conforti, F. D., & Davis, S. F. (2006). The effect of soya flour and flaxseed as a partial replacement for bread flour in yeast bread. International Journal of Food Science & Technology, 41(s2), 95-101. http://dx.doi.org/10.1111/j.1365-2621.2006.01410.x
    » http://dx.doi.org/10.1111/j.1365-2621.2006.01410.x
  • Dash, K. K., Kumar, A., Kumari, S., & Malik, M. A. (2021). Silver nanoparticle incorporated flaxseed-alginate composite films: effect of physicochemical, mechanical, and thermal properties. Journal of Polymers and the Environment, 29(11), 3649-3659. http://dx.doi.org/10.1007/s10924-021-02137-y
    » http://dx.doi.org/10.1007/s10924-021-02137-y
  • Dev, D. K., & Quensel, L. (1989). Functional properties of linseed protein products containing different levels of mucilage in selected food systems. Journal of Food Science, 54(1), 183-186. http://dx.doi.org/10.1111/j.1365-2621.1989.tb08597.x
    » http://dx.doi.org/10.1111/j.1365-2621.1989.tb08597.x
  • Doyen, A., Udenigwe, C. C., Mitchell, P. L., Marette, A., Aluko, R. E., & Bazinet, L. (2014). Anti-diabetic and antihypertensive activities of two flaxseed protein hydrolysate fractions revealed following their simultaneous separation by electrodialysis with ultrafiltration membranes. Food Chemistry, 145, 66-76. http://dx.doi.org/10.1016/j.foodchem.2013.07.108 PMid:24128450.
    » http://dx.doi.org/10.1016/j.foodchem.2013.07.108
  • Drozlowska, E., Lopusiewicz, L., Mezynska, M., & Bartkowiak, A. (2020). The effect of native and denaturated flaxseed meal extract on physiochemical properties of low fat mayonnaises. Journal of Food Measurement and Characterization, 14(2), 1135-1145. http://dx.doi.org/10.1007/s11694-019-00363-6
    » http://dx.doi.org/10.1007/s11694-019-00363-6
  • Food and Agriculture Organization – FAO. (2020). Retrieved from http://www.fao.org/faostat/zh/#data/QC
    » http://www.fao.org/faostat/zh/#data/QC
  • Franck, M., Perreault, V., Suwal, S., Marciniak, A., Bazinet, L., & Doyen, A. (2019). High hydrostatic pressure-assisted enzymatic hydrolysis improved protein digestion of flaxseed protein isolate and generation of peptides with antioxidant activity. Food Research International, 115, 467-473. http://dx.doi.org/10.1016/j.foodres.2018.10.034 PMid:30599966.
    » http://dx.doi.org/10.1016/j.foodres.2018.10.034
  • Gambuś, H., Gambuś, F., Pastuszka, D., Wrona, P., Ziobro, R., Sabat, R., Mickowska, B., Nowotna, A., & Sikora, M. (2009). Quality of gluten-free supplemented cakes and biscuits. International Journal of Food Sciences and Nutrition, 60(Suppl. 4), 31-50. http://dx.doi.org/10.1080/09637480802375523 PMid:19330630.
    » http://dx.doi.org/10.1080/09637480802375523
  • Ganorkar, P. M., Patel, J. M., Shah, V., & Rangrej, V. V. (2016). Defatted flaxseed meal incorporated corn-rice flour blend based extruded product by response surface methodology. Journal of Food Science and Technology, 53(4), 1867-1877. http://dx.doi.org/10.1007/s13197-015-2134-3 PMid:27413213.
    » http://dx.doi.org/10.1007/s13197-015-2134-3
  • Giacomino, S., Peñas, E., Ferreyra, V., Pellegrino, N., Fournier, M., Apro, N., Carrión, M. O., & Frias, J. (2013). Extruded flaxseed meal enhances the nutritional quality of cereal-based products. Plant Foods for Human Nutrition (Dordrecht, Netherlands), 68(2), 131-136. http://dx.doi.org/10.1007/s11130-013-0359-8 PMid:23640296.
    » http://dx.doi.org/10.1007/s11130-013-0359-8
  • Hall, C., Tulbek, M. C., & Xu, Y. (2006). Flaxseed. In S. L. Taylor (Ed.), Advance in food and nutrition research (pp. 1-97). Boston: Elsevier.
  • Hussain, S., Anjum, F. M., Butt, M. S., Khan, M. I., & Asghar, A. (2006). Physical and sensoric attributes of flaxseed flour supplemented cookies. Turkish Journal of Biology, 30, 87-92.
  • Hwang, C. F., Chen, Y. A., Luo, C., & Chiang, W. D. (2016). Antioxidant and antibacterial activities of peptide fractions from flaxseed protein hydrolysed by protease from Bacillus altitudinis HK02. International Journal of Food Science & Technology, 51(3), 681-689. http://dx.doi.org/10.1111/ijfs.13030
    » http://dx.doi.org/10.1111/ijfs.13030
  • Juodeikiene, G., Zadeike, D., Trakselyte-Rupsiene, K., Gasauskaite, K., Bartkiene, E., Lele, V., Viskelis, P., Bernatoniene, J., Ivanauskas, L., & Jakstas, V. (2020). Functionalisation of flaxseed proteins assisted by ultrasonication to produce coatings enriched with raspberries phytochemicals. Lebensmittel-Wissenschaft + Technologie, 124, 109180. http://dx.doi.org/10.1016/j.lwt.2020.109180
    » http://dx.doi.org/10.1016/j.lwt.2020.109180
  • Karaca, A. C., Low, N., & Nickerson, M. (2011). Emulsifying properties of canola and flaxseed protein isolates produced by isoelectric precipitation and salt extraction. Food Research International, 44(9), 2991-2998. http://dx.doi.org/10.1016/j.foodres.2011.07.009
    » http://dx.doi.org/10.1016/j.foodres.2011.07.009
  • Karamać, M., Kosińskacagnazzo, A., & Kulczyk, A. (2016). Use of different proteases to obtain flaxseed protein hydrolysates with antioxidant activity. International Journal of Molecular Sciences, 17(7), 1027-1039. http://dx.doi.org/10.3390/ijms17071027 PMid:27367678.
    » http://dx.doi.org/10.3390/ijms17071027
  • Kaushik, P., Dowling, K., McKnight, S., Barrow, C. J., Wang, B., & Adhikari, B. (2016). Preparation, characterization and functional properties of flax seed protein isolate. Food Chemistry, 197(Part A), 212-220. http://dx.doi.org/10.1016/j.foodchem.2015.09.106 PMid:26616943.
    » http://dx.doi.org/10.1016/j.foodchem.2015.09.106
  • Khan, N. A., Booker, H., & Yu, P. (2015). Effect of heating method on alteration of protein molecular structure in flaxseed: Relationship with changes in protein subfraction profile and digestion in dairy cows. Journal of Agricultural and Food Chemistry, 63(4), 1057-1066. http://dx.doi.org/10.1021/jf503575y PMid:25578477.
    » http://dx.doi.org/10.1021/jf503575y
  • Koca, A. F., & Anil, M. (2007). Effect of flaxseed and wheat flour blends on dough rheology and bread quality. Journal of the Science of Food and Agriculture, 8(6), 1172-1175. http://dx.doi.org/10.1002/jsfa.2739
    » http://dx.doi.org/10.1002/jsfa.2739
  • Krause, J. P., Schultz, M., & Dudek, S. (2010). Effect of extraction conditions on composition, surface activity and rheological properties of protein isolations from flaxseed (Linum usitativissimum L.). Journal of the Science of Food and Agriculture, 82(9), 970-976. http://dx.doi.org/10.1002/jsfa.1140
    » http://dx.doi.org/10.1002/jsfa.1140
  • Kuang, X., Kong, Y., Hu, X., Li, K., Guo, X., Liu, C., Han, L., & Li, D. (2020). Defatted flaxseed flour improves weight loss and lipid profile in overweight and obese adults: a randomized controlled trial. Food & Function, 11(9), 8237-8247. http://dx.doi.org/10.1039/D0FO00838A PMid:32966475.
    » http://dx.doi.org/10.1039/D0FO00838A
  • Lan, Y., Ohm, J. B., Chen, B., & Rao, J. (2020). Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids, 104, 105731. http://dx.doi.org/10.1016/j.foodhyd.2020.105731
    » http://dx.doi.org/10.1016/j.foodhyd.2020.105731
  • Langyan, S., Khan, F. N., Yadava, P., Alhazmi, A., Mahmoud, S. F., Saleh, D. I., Zuan, A. T. K., & Kumar, A. (2021). In silico proteolysis and analysis of bioactive peptides from sequences of fatty acid desaturase 3 (FAD3) of flaxseed protein. Saudi Journal of Biological Sciences, 28(10), 5480-5489. http://dx.doi.org/10.1016/j.sjbs.2021.08.027 PMid:34588858.
    » http://dx.doi.org/10.1016/j.sjbs.2021.08.027
  • Lei, B., Li-Chan, E. C. Y., Oomah, B. D., & Mazza, G. (2003). Distribution of cadmium-binding components in flax (Linum usitatissimum L.) seed. Journal of Agricultural and Food Chemistry, 51(3), 814-821. http://dx.doi.org/10.1021/jf0209084 PMid:12537463.
    » http://dx.doi.org/10.1021/jf0209084
  • Li, T., & Hao, J. (2013). A peeling method and machine for flaxseeds. CN: 201310630673: A.
  • Lim, C. W., Norziah, M. H., & Lu, H. F. S. (2010). Effect of flaxseed oil towards physico-chemical and sensory characteristic of reduced fat ice creams and its stability in ice creams upon storage. International Food Research Journal, 17, 393-403.
  • Lipilina, E., & Ganji, V. (2009). Incorporation of ground flaxseed into bakery products and its effect on sensory and nutritional characteristics: a pilot study. Journal of Food Service, 20(1), 52-59. http://dx.doi.org/10.1111/j.1748-0159.2008.00124.x
    » http://dx.doi.org/10.1111/j.1748-0159.2008.00124.x
  • Liu, J., Shim, Y. Y., Tse, T. J., Wang, Y., & Reaney, M. J. T. (2018). Flaxseed gum a versatile natural hydrocolloid for food and non-food applications. Trends in Food Science & Technology, 75, 146-157. http://dx.doi.org/10.1016/j.tifs.2018.01.011
    » http://dx.doi.org/10.1016/j.tifs.2018.01.011
  • Logarušić, M., Radošević, K., Bis, A., Panić, M., Slivac, I., & Srček, V. G. (2020). Biological potential of flaxseed protein hydrolysates obtained by different proteases. Plant Foods for Human Nutrition, 75(4), 518-524. http://dx.doi.org/10.1007/s11130-020-00841-z PMid:32766942.
    » http://dx.doi.org/10.1007/s11130-020-00841-z
  • Luna-Vital, D. A., Mojica, L., Mejía, E. G., Mendoza, S., & Loarca-Piña, G. (2015). Biological potential of protein hydrolysates and peptides from common bean (Phaseolus vulgaris L.): a review. Food Research International, 76, 39-50. http://dx.doi.org/10.1016/j.foodres.2014.11.024
    » http://dx.doi.org/10.1016/j.foodres.2014.11.024
  • Lv, B., & Huang, C.X. (2015). Flaxseed sprouted powder and a preparation method thereof. CN 201510030685: A.
  • Madhusudhan, K. T., & Singh, N. (1985a). Effect of detoxification treatment on the physicochemical properties of linseed proteins. Journal of Agricultural and Food Chemistry, 33(6), 1219-1222. http://dx.doi.org/10.1021/jf00066a051
    » http://dx.doi.org/10.1021/jf00066a051
  • Madhusudhan, K. T., & Singh, N. (1985b). Isolation and characterization of the major fraction (12S) of linseed proteins. Journal of Agricultural and Food Chemistry, 33(4), 673-677. http://dx.doi.org/10.1021/jf00064a026
    » http://dx.doi.org/10.1021/jf00064a026
  • Manthey, F., Sinha, S., Wolf-Hall, C., & Hall, C. III (2008). Effect of flaxseed flour and packaging on shelf life of refrigerated pasta. Journal of Food Processing and Preservation, 32(1), 75-87. http://dx.doi.org/10.1111/j.1745-4549.2007.00166.x
    » http://dx.doi.org/10.1111/j.1745-4549.2007.00166.x
  • Marambe, H. K., & Wanasundara, J. P. D. (2017). Protein from flaxseed (Linum usitatissimum L.). In S. R. Nadathur, J.P.D. Wanasundara & L. Scanlin (Eds.), Sustainable protein sources (pp. 133-144). UK: Academics Press. http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1
    » http://dx.doi.org/10.1016/B978-0-12-802778-3.00008-1
  • Marambe, H. K., Shand, P. J., & Wanasundara, J. P. D. (2011). Release of angiotensin I-converting enzyme inhibitory peptides from flaxseed (Linum usitatissimum L.) protein under simulated gastrointestinal digestion. Journal of Agricultural and Food Chemistry, 59(17), 9596-9604. http://dx.doi.org/10.1021/jf202000e PMid:21776963.
    » http://dx.doi.org/10.1021/jf202000e
  • Marambe, H. K., Shand, P. J., & Wanasundara, J. P. D. (2013). In vitro digestibility of flaxseed (Linum usitatissimum L.) protein: effect of seed mucilage, oil and thermal processing. International Journal of Food Science & Technology, 48(3), 628-635. http://dx.doi.org/10.1111/ijfs.12008
    » http://dx.doi.org/10.1111/ijfs.12008
  • Marambe, P. W. M. L. H. K., Shand, P. J., & Wanasundara, J. P. D. (2008). An in vitro investigation of selected biological activities of hydrolyzed flaxseed (Linum usitatissimum L.) proteins. Journal of the American Oil Chemists’ Society, 85(12), 1155-1164. http://dx.doi.org/10.1007/s11746-008-1293-z
    » http://dx.doi.org/10.1007/s11746-008-1293-z
  • Marie, G. C. U., Perreault, V., Henaux, L., Carnovale, V., Aluko, R. E., Marette, A., Doyen, A., & Bazinet, L. (2019). Impact of a high hydrostatic pressure pretreatment on the separation of bioactive peptides from flaxseed protein hydrolysates by electrodialysis with ultrafiltration membranes. Separation and Purification Technology, 211, 242-251. http://dx.doi.org/10.1016/j.seppur.2018.09.063
    » http://dx.doi.org/10.1016/j.seppur.2018.09.063
  • Martínez-Flores, H., Barrera, E., Garnica-Romo, M., Penagos, C., Saavedra, J., & Macazaga-Alvarez, R. (2006). Functional characteristics of protein flaxseed concentrate obtained applying a response surface methodology. Journal of Food Science, 71(8), 495-498. http://dx.doi.org/10.1111/j.1750-3841.2006.00147.x
    » http://dx.doi.org/10.1111/j.1750-3841.2006.00147.x
  • Mohamed, R. S., Fouda, K., & Akl, E. M. (2020). Hepatorenal protective effect of flaxseed protein isolate incorporated in lemon juice against lead toxicity in rats. Toxicology Reports, 7, 30-35. http://dx.doi.org/10.1016/j.toxrep.2019.12.001 PMid:31890606.
    » http://dx.doi.org/10.1016/j.toxrep.2019.12.001
  • Mridula, D., Barnwal, P., Gurumayum, S., & Singh, K. K. (2014). Effect of chemical pretreatment on dehulling parameters of flaxseed (cv. Garima). Journal of Food Science and Technology, 51(9), 2228-2233. http://dx.doi.org/10.1007/s13197-012-0699-7 PMid:25190888.
    » http://dx.doi.org/10.1007/s13197-012-0699-7
  • Mueller, K., Eisner, P., Yoshie-Stark, Y., Nakada, R., & Kirchhoff, E. (2010). Functional properties and chemical composition of fractionated brown and yellow linseed meal (Linum usitatissimum L.). Journal of Food Engineering, 98(4), 453-460. http://dx.doi.org/10.1016/j.jfoodeng.2010.01.028
    » http://dx.doi.org/10.1016/j.jfoodeng.2010.01.028
  • Nasrabadi, M. N., Goli, S. A. H., Doost, A. S., Roman, B., Dewettinck, K., Stevens, C. V., & Van Der Meeren, P. V. (2019). Plant based pickering stabilization of emulsions using soluble flaxseed protein and mucilage nano-assemblies. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 563, 170-182. http://dx.doi.org/10.1016/j.colsurfa.2018.12.004
    » http://dx.doi.org/10.1016/j.colsurfa.2018.12.004
  • Nie, C., Qin, X., Duan, Z., Huang, S., Yu, X., Deng, Q., Xiang, Q., & Geng, F. (2021). Comparative structural and techno-functional elucidation of full-fat and defatted flaxseed extracts: implication of atmospheric pressure plasma jet. Journal of the Science of Food and Agriculture, 102(2), 823-835. PMid:34232506.
  • Nwachukwu, I. D., & Aluko, R. E. (2018a). Antioxidant properties of flaxseed protein hydrolysates: influence of hydrolytic enzyme concentration and peptide size. Journal of the American Oil Chemists’ Society, 95(8), 1105-1118. http://dx.doi.org/10.1002/aocs.12042
    » http://dx.doi.org/10.1002/aocs.12042
  • Nwachukwu, I. D., & Aluko, R. E. (2018b). Physicochemical and emulsification properties of flaxseed (Linum usitatissimum L.) albumin and globulin fractions. Food Chemistry, 255, 216-225. http://dx.doi.org/10.1016/j.foodchem.2018.02.068 PMid:29571469.
    » http://dx.doi.org/10.1016/j.foodchem.2018.02.068
  • Nwachukwu, I. D., Girgih, A. T., Malomo, S. A., Onuh, J. O., & Aluko, R. E. (2014). Thermoase-derived flaxseed protein hydrolysates and membrane ultrafiltration peptide fractions have systolic blood pressure-lowering effects in spontaneously hypertensive rats. International Journal of Molecular Sciences, 15(10), 18131-18147. http://dx.doi.org/10.3390/ijms151018131 PMid:25302619.
    » http://dx.doi.org/10.3390/ijms151018131
  • Omoni, A. O., & Aluko, R. E. (2006a). Effect of cationic flaxseed protein hydrolysate fractions on the in vitro structure and activity of calmodulin-dependent endothelial nitric oxide synthase. Molecular Nutrition & Food Research, 50(10), 958-966. http://dx.doi.org/10.1002/mnfr.200600041 PMid:16967519.
    » http://dx.doi.org/10.1002/mnfr.200600041
  • Omoni, A. O., & Aluko, R. E. (2006b). Mechanism of the inhibition of calmodulin-dependent neuronal nitric oxide synthase by flaxseed protein hydrolysates. Journal of the American Oil Chemists’ Society, 83(4), 335-340. http://dx.doi.org/10.1007/s11746-006-1209-8
    » http://dx.doi.org/10.1007/s11746-006-1209-8
  • Oomah, B. D. (2001). Flaxseed as a functional food source. Journal of the Science of Food and Agriculture, 81(9), 889-894. http://dx.doi.org/10.1002/jsfa.898
    » http://dx.doi.org/10.1002/jsfa.898
  • Oomah, B. D., & Mazza, G. (1993). Processing of flaxseed meal: effect of solvent extraction on physicochemical characteristics. Lebensmittel-Wissenschaft + Technologie, 26(4), 312-317. http://dx.doi.org/10.1006/fstl.1993.1064
    » http://dx.doi.org/10.1006/fstl.1993.1064
  • Perreault, V., Henaux, L., Bazinet, L., & Doyen, A. (2017). Pretreatment of flaxseed protein isolate by high hydrostatic pressure: impacts on protein structure, enzymatic hydrolysis and final hydrolysate antioxidant capacities. Food Chemistry, 221, 1805-1812. http://dx.doi.org/10.1016/j.foodchem.2016.10.100 PMid:27979166.
    » http://dx.doi.org/10.1016/j.foodchem.2016.10.100
  • Pham, L. B., Wang, B., Zisu, B., & Adhikari, B. (2019a). Complexation between flaxseed protein isolate and phenolic compounds: effect on interfacial, emulsifying and antioxidant properties of emulsions. Food Hydrocolloids, 94, 20-29. http://dx.doi.org/10.1016/j.foodhyd.2019.03.007
    » http://dx.doi.org/10.1016/j.foodhyd.2019.03.007
  • Pham, L. B., Wang, B., Zisu, B., & Adhikari, B. (2019b). Covalent modification of flaxseed protein isolate by phenolic compounds and the structure and functional properties of the adducts. Food Chemistry, 293, 463-471. http://dx.doi.org/10.1016/j.foodchem.2019.04.123 PMid:31151635.
    » http://dx.doi.org/10.1016/j.foodchem.2019.04.123
  • Pham, L. B., Wang, B., Zisu, B., Truong, T., & Adhikari, B. (2020). Microencapsulation of flaxseed oil using polyphenol-adducted flaxseed protein isolate-flaxseed gum complex coacervates. Food Hydrocolloids, 107, 105944. http://dx.doi.org/10.1016/j.foodhyd.2020.105944
    » http://dx.doi.org/10.1016/j.foodhyd.2020.105944
  • Pohjanheimo, T. A., Hakala, M. A., Tahvonen, R. L., Salminen, S. J., & Kallio, H. P. (2006). Flaxseed in bread making: effects on sensory quality, aging, and composition of bakery products. Journal of Food Science, 71(4), 343-348. http://dx.doi.org/10.1111/j.1750-3841.2006.00005.x
    » http://dx.doi.org/10.1111/j.1750-3841.2006.00005.x
  • Rabetafika, H. N., Van Remoortel, V. V., Danthine, S., Paquot, M., & Blecker, C. (2011). Flaxseed proteins: food uses and health benefits. International Journal of Food Science & Technology, 46(2), 221-228. http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x
    » http://dx.doi.org/10.1111/j.1365-2621.2010.02477.x
  • Ribeiro, B. D., Barreto, D. W., & Coelho, M. A. (2013). Enzyme-enhanced extraction of phenolic compounds and proteins from flaxseed meal. ISRN Biotechnology, 2013, 521067. http://dx.doi.org/10.5402/2013/521067 PMid:25969774.
    » http://dx.doi.org/10.5402/2013/521067
  • Rodrigues, R. T., Fanaro, G. B., Duarte, R. C., Koike, A. C., & Villavicencio, A. L. C. H. (2012). A sensory evaluation of irradiated cookies made from flaxseed meal. Radiation Physics and Chemistry, 81(8), 1157-1159. http://dx.doi.org/10.1016/j.radphyschem.2012.02.001
    » http://dx.doi.org/10.1016/j.radphyschem.2012.02.001
  • Sa, A. G. A., Silva, D. G., Pacheco, M. T. B., Moreno, Y. M. F., & Carciofi, B. A. M. (2021). Oilseed by-products as plant-based protein sources: amino acid profile and digestibility. Future Foods, 3, 100023. http://dx.doi.org/10.1016/j.fufo.2021.100023
    » http://dx.doi.org/10.1016/j.fufo.2021.100023
  • Safdar, B., Pang, Z., Liu, X., Rashid, M. T., & Jatoi, M. A. (2020). Structural and functional properties of raw and defatted flaxseed flour and degradation of cyanogenic contents using different processing methods. Journal of Food Process Engineering, 43(6), e13406. http://dx.doi.org/10.1111/jfpe.13406
    » http://dx.doi.org/10.1111/jfpe.13406
  • Sammour, R. H. (1999). Proteins of linseed (Linum usitatissimum L.), extraction and characterization by electrophoresis. Botanical Bulletin of Academia Sinica, 40, 121-126.
  • Sammour, R. H., El-Shourbagy, M. N., Abo-Shady, A. M., & Abasary, A. M. (1994). The seed proteins of linseed (Linum usitativissimum L.). Bulletin of Botany Academia Sinica, 35, 171-177.
  • Sarabandi, K., & Jafari, S. M. (2020a). Fractionation of flaxseed-derived bioactive peptides and their influence on nanoliposomal carriers. Journal of Agricultural and Food Chemistry, 68(51), 15097-15106. http://dx.doi.org/10.1021/acs.jafc.0c02583 PMid:33290068.
    » http://dx.doi.org/10.1021/acs.jafc.0c02583
  • Sarabandi, K., & Jafari, S. M. (2020b). Improving the antioxidant stability of flaxseed peptide fractions during spray drying encapsulation by surfactants: physicochemical and morphological features. Journal of Food Engineering, 286, 110131. http://dx.doi.org/10.1016/j.jfoodeng.2020.110131
    » http://dx.doi.org/10.1016/j.jfoodeng.2020.110131
  • Sharma, M., & Saini, C. S. (2021). Postharvest shelf-life extension of fresh-cut guavas (Psidium guajava) using flaxseed protein-based composite coatings. Food Hydrocolloids for Health, 1, 100015. http://dx.doi.org/10.1016/j.fhfh.2021.100015
    » http://dx.doi.org/10.1016/j.fhfh.2021.100015
  • Shearer, A. E. H., & Davies, C. G. A. (2005). Physicochemical properties of freshly baked and stored whole-wheat muffins with and without flaxseed meal. Journal of Food Quality, 28(2), 137-153. http://dx.doi.org/10.1111/j.1745-4557.2005.00004.x
    » http://dx.doi.org/10.1111/j.1745-4557.2005.00004.x
  • Shevkani, K., Singh, N., Kaur, A., & Rana, J. C. (2015). Structural and functional characterization of kidney bean and field pea protein isolates: a comparative study. Food Hydrocolloids, 43, 679-689. http://dx.doi.org/10.1016/j.foodhyd.2014.07.024
    » http://dx.doi.org/10.1016/j.foodhyd.2014.07.024
  • Shi, J., Xiao, J., Liu, L., & Dong, X. (2021). Ultrasonic assisted oil-in-water emulsions stabilized by flaxseed protein isolate: influence of different oils. Journal of Dispersion Science and Technology, 1-12. http://dx.doi.org/10.1080/01932691.2021.1880923
    » http://dx.doi.org/10.1080/01932691.2021.1880923
  • Shim, Y. Y., Gui, B., Wang, Y., & Reaney, M. J. T. (2015). Flaxseed (Linum usitatissimum L.) oil processing and selected products. Trends in Food Science & Technology, 43(2), 162-177. http://dx.doi.org/10.1016/j.tifs.2015.03.001
    » http://dx.doi.org/10.1016/j.tifs.2015.03.001
  • Silva, F. G. D., Hernandez-Ledesma, B., Amigo, L., Netto, F. M., & Miralles, B. (2017). Identification of peptides released from flaxseed (Linum usitatissimum) protein by Alclase hydrolysis: antioxidant activity. Lebensmittel-Wissenschaft + Technologie, 76, 140-146. http://dx.doi.org/10.1016/j.lwt.2016.10.049
    » http://dx.doi.org/10.1016/j.lwt.2016.10.049
  • Slominski, B. A., Meng, X., Campbell, L. D., Guenter, W., & Jones, O. (2006). The use of enzyme technology for improved energy utilization from full-fat oilseeds. Part II: Flaxseed. Poultry Science, 85(6), 1031-1037. http://dx.doi.org/10.1093/ps/85.6.1031 PMid:16776472.
    » http://dx.doi.org/10.1093/ps/85.6.1031
  • Song, X., Zhang, L., Jing, C., Kang, Q., Wu, G., Jiang, W., & Yuan, H. (2017). Study on degumming process of flaxseed by enzymatic hydrolysis. Heilongjiang Nongye Kexue, 12, 67-69.
  • Tang, Z. X. (2019a). Flaxseed fat-reducing yogurt nutrition bar and a preparation method thereof. CN 201910603833.X.
  • Tang, Z. X. (2019b). Flaxseed yogurt for women and a making method thereof. CN 201910814791.
  • Tang, Z. X., & Bian, J. Z. (2018a). Flaxseed nutritional food for lowing blood lipid and a preparation method thereof. CN 201811366312:A.
  • Tang, Z. X., & Bian, J. Z. (2018b). Flaxseed nutritional food for strengthening brain and a production method thereof. CN 201811367137: A.
  • Tang, Z. X., & Bian, J. Z. (2018c). Flaxseed protein beverage and a preparation method thereof. CN 201811252507: A.
  • Tang, Z. X., & Bian, J. Z. (2018d). Nourishment enriched in proteins and flaxseed oil and a preparation method thereof. CN 201811252511.7.
  • Tang, Z. X., & Bian, J. Z. (2018e). Pregnant woman food containing alpha-linolenic acid and a preparation method thereof. CN 201811367386:A.
  • Tang, Z. X., Liang, J. Y., & Bian, J. Z. (2016a). Coarse cereal biscuits containing alpha-linolenic acid and a preparation method thereof. CN 201610762274: A.
  • Tang, Z. X., Liang, J. Y., & Bian, J. Z. (2016b). Flaxseed milk tablets and a preparation method thereof. CN 201610757720: A.
  • Tang, Z. X., Liang, J. Y., & Bian, J. Z. (2016c). Flaxseed soft sweets and a preparation method thereof. CN 201610755288: A.
  • Tang, Z. X., Liang, J. Y., & Bian, J. Z. (2016d). Nutritious coarse cereal energy bar and a making method thereof. CN 201610754178: A.
  • Tang, Z. X., Liang, J. Y., & Bian, J. Z. (2017). Flaxseed kernel protein beverage and a preparation method thereof. CN 201710047917: A.
  • Tang, Z. X., Shi, L. E., Wang, X. M., Dai, G. W., Cheng, L. A., Wan, Z. X., He, H., Wu, Q., Wang, Y. B., Jin, X. Y., Ying, R. F., & Huang, L. H. (2020). Whole flaxseed-based products and their health benefits. Food Science and Technology Research, 26(5), 561-578. http://dx.doi.org/10.3136/fstr.26.561
    » http://dx.doi.org/10.3136/fstr.26.561
  • Tang, Z. X., Ying, R. F., Lv, B. F., Yang, L. H., Xu, Z., Yan, L. Q., Bu, J. Z., & Wei, Y. S. (2021). Flaxseed oil: extraction, health benefits and products. Quality Assurance and Safety of Crops & Foods, 13(1), 1-19. http://dx.doi.org/10.15586/qas.v13i1.783
    » http://dx.doi.org/10.15586/qas.v13i1.783
  • Teh, S. S., Bekhit, A. E. A., Carne, A., & Birch, J. (2016). Antioxidant and ACE-inhibitory activities of hemp (Cannabis sativa L.) protein hydrolysates produced by the proteases AFP, HT, Pro-G, actinidin and zingibain. Food Chemistry, 203, 199-206. http://dx.doi.org/10.1016/j.foodchem.2016.02.057 PMid:26948606.
    » http://dx.doi.org/10.1016/j.foodchem.2016.02.057
  • Teh, S. S., Bekhit, E. D., Carne, A., & Birch, J. (2014). Effect of the defatting process, acid and alkali extraction on the physicochemical and functional properties of hemp, flax and canola seed cake protein isolates. Journal of Food Measurement and Characterization, 8(2), 92-104. http://dx.doi.org/10.1007/s11694-013-9168-x
    » http://dx.doi.org/10.1007/s11694-013-9168-x
  • Tirgar, M., Silcock, P., Carne, A., & Birch, E. J. (2017). Effect of extraction method on functional properties of flaxseed protein concentrates. Food Chemistry, 215, 417-424. http://dx.doi.org/10.1016/j.foodchem.2016.08.002 PMid:27542494.
    » http://dx.doi.org/10.1016/j.foodchem.2016.08.002
  • Udenigwe, C. C., & Aluko, R. E. (2010). Antioxidant and angiotensin converting enzyme-inhibitory properties of a flaxseed protein-derived high fischer ratio peptide mixture. Journal of Agricultural and Food Chemistry, 58(8), 4762-4768. http://dx.doi.org/10.1021/jf100149w PMid:20218606.
    » http://dx.doi.org/10.1021/jf100149w
  • Udenigwe, C. C., & Aluko, R. E. (2011). Another side of flaxseed proteins and peptides. Agro Food Industry Hi-Tech, 22, 50-53.
  • Udenigwe, C. C., & Aluko, R. E. (2012). Multifunctional cationic peptide fractions from flaxseed protein hydrolysates. Plant Foods for Human Nutrition (Dordrecht, Netherlands), 67(1), 1-9. http://dx.doi.org/10.1007/s11130-012-0275-3 PMid:22327315.
    » http://dx.doi.org/10.1007/s11130-012-0275-3
  • Udenigwe, C. C., Adebiyi, A. P., Doyen, A., Li, H., Bazinet, L., & Aluko, R. E. (2012). Low molecular weight flaxseed protein-derived arginine-containing peptides reduced blood pressure of spontaneously hypertensive rats faster than amino acid form of arginine and native flaxseed protein. Food Chemistry, 132(1), 468-475. http://dx.doi.org/10.1016/j.foodchem.2011.11.024 PMid:26434317.
    » http://dx.doi.org/10.1016/j.foodchem.2011.11.024
  • Udenigwe, C. C., Lin, Y. S., Hou, W. C., & Aluko, R. E. (2009). Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions. Journal of Functional Foods, 1(2), 199-207. http://dx.doi.org/10.1016/j.jff.2009.01.009
    » http://dx.doi.org/10.1016/j.jff.2009.01.009
  • Wanasundara, P. K. J. P. D., & Shahidi, F. (1997). Removal of flaxseed mucilage by chemical and enzymatic treatments. Food Chemistry, 59(1), 47-55. http://dx.doi.org/10.1016/S0308-8146(96)00093-3
    » http://dx.doi.org/10.1016/S0308-8146(96)00093-3
  • Wanasundara, P. K. J. P. D., & Shahidi, F. (2003). Flaxseed proteins: potential food applications and process-induced changes. In L. U. Thompson & S. C. Cunnane (Eds.), Flaxseed in human nutrition (pp. 387-403). Champaign: AOCS Press. http://dx.doi.org/10.1201/9781439831915.ch21
    » http://dx.doi.org/10.1201/9781439831915.ch21
  • Wanasundara, P. K. J. P. D., Wanasundara, U. N., & Shahidi, F. (1999). Changes in flax (Linum usitatissimum L.) seed lipids during germination. Journal of the American Oil Chemists’ Society, 76(1), 41-48. http://dx.doi.org/10.1007/s11746-999-0045-z
    » http://dx.doi.org/10.1007/s11746-999-0045-z
  • Wang, B., Li, D., Wang, L., & Özkan, N. (2010). Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions. Journal of Food Engineering, 96(4), 555-561. http://dx.doi.org/10.1016/j.jfoodeng.2009.09.001
    » http://dx.doi.org/10.1016/j.jfoodeng.2009.09.001
  • Wang, Y., Li, D., Wang, L. J., Chiu, Y. L., Chen, X. D., Mao, Z. H., & Song, C. F. (2008). Optimization of extrusion of flaxseeds for in vitro protein digestibility analysis using response surface methodology. Journal of Food Engineering, 85(1), 59-64. http://dx.doi.org/10.1016/j.jfoodeng.2007.06.033
    » http://dx.doi.org/10.1016/j.jfoodeng.2007.06.033
  • Waszkowiak, K., & Rudzinska, M. (2014). Effect of flaxseed meal and extracts on lipid stability in a stored meat product. Journal of the American Oil Chemists’ Society, 91(6), 979-987. http://dx.doi.org/10.1007/s11746-014-2438-x PMid:24882871.
    » http://dx.doi.org/10.1007/s11746-014-2438-x
  • Wei, C. K., Ni, Z. J., Thakur, K., Liao, A. M., Huang, J. H., & Wei, Z. J. (2019). Color and flavor of flaxseed protein hydrolysates Maillard reaction products: effect of cysteine, initial pH, and thermal treatment. International Journal of Food Properties, 22(1), 84-99. http://dx.doi.org/10.1080/10942912.2019.1573830
    » http://dx.doi.org/10.1080/10942912.2019.1573830
  • Wei, C. K., Thakur, K., Liu, D. H., Zhang, J. G., & Wei, Z. J. (2018). Enzymatic hydrolysis of flaxseed (Linum usitatissimum L.) protein and sensory characterization of Maillard reaction products. Food Chemistry, 263, 186-193. http://dx.doi.org/10.1016/j.foodchem.2018.04.120 PMid:29784306.
    » http://dx.doi.org/10.1016/j.foodchem.2018.04.120
  • Wu, J.P., Muir, A.D., & Aluko, R.E. (2009). AEC inhibitory peptides from plant materials. Patent No. US007566690B2.
  • Wu, S., Wang, X., Qi, W., & Guo, Q. (2019). Bioactive protein/peptides of flaxseed: a review. Trends in Food Science & Technology, 92, 184-193. http://dx.doi.org/10.1016/j.tifs.2019.08.017
    » http://dx.doi.org/10.1016/j.tifs.2019.08.017
  • Xu, Y., Hall, C. III, & Wolf-Hall, C. (2008a). Antifungal activity stability of flaxseed protein extract using response surface methodology. Journal of Food Science, 73(1), M9-M14. http://dx.doi.org/10.1111/j.1750-3841.2007.00576.x PMid:18211360.
    » http://dx.doi.org/10.1111/j.1750-3841.2007.00576.x
  • Xu, Y., Hall, C. III, & Wolf-Hall, C. (2008b). Fungistatic activity of heat-treated flaxseed determined by response surface methodology. Journal of Food Science, 73(6), M250-M256. http://dx.doi.org/10.1111/j.1750-3841.2008.00806.x PMid:19241553.
    » http://dx.doi.org/10.1111/j.1750-3841.2008.00806.x
  • Yang, J., Wen, C., Duan, Y., Deng, Q., Peng, D., Zhang, H., & Ma, H. (2021). The composition, extraction, analysis, bioactivities, bioavailability and application in food system of flaxseed (Linum usitatissimum L.) oil: a review. Trends in Food Science & Technology, 118, 252-260. http://dx.doi.org/10.1016/j.tifs.2021.09.025
    » http://dx.doi.org/10.1016/j.tifs.2021.09.025
  • Yoshie-Stark, Y., Müller, K., Kawarada, H., Futagawa, K., Nakada, R., & Tashiro, Y. (2011). Functional properties of linseed meal fractions: application as nutraceutical ingredient. Food Science and Technology Research, 17(4), 301-310. http://dx.doi.org/10.3136/fstr.17.301
    » http://dx.doi.org/10.3136/fstr.17.301
  • Yu, X., Huang, S., Nie, C., Deng, Q., Zhai, Y., & Shen, R. (2020). Effects of atmospheric pressure plasma jet on the physicochemical, functional, and antioxidant properties of flaxseed protein. Journal of Food Science, 85(7), 2010-2019. http://dx.doi.org/10.1111/1750-3841.15184 PMid:32529640.
    » http://dx.doi.org/10.1111/1750-3841.15184
  • Zardo, D. M., Dantas, A. P., Vanz, R., Wosiacki, G., & Nogueira, A. (2009). Intensity of red pigmentation in apples and its influence on phenolic compounds content and antioxidant activity. Food Science and Technology, 29(1), 148-154. http://dx.doi.org/10.1590/S0101-20612009000100023
    » http://dx.doi.org/10.1590/S0101-20612009000100023
  • Zheng, Y. I., Wiesenborn, D. P., Tostenson, K., & Kangas, N. (2003). Screw pressing of whole and dehulled flaxseed for organic oil. Journal of the American Oil Chemists’ Society, 80(10), 1039-1045. http://dx.doi.org/10.1007/s11746-003-0817-7
    » http://dx.doi.org/10.1007/s11746-003-0817-7
  • Zou, X., Chen, X., Hu, J., Wang, Y., Gong, D., Zhu, X., & Deng, Z. (2017). Comparisons of proximate compositions, fatty acids profile and micronutrients between fiber and oil flaxseeds (Linum usitatissimum L.). Journal of Food Composition and Analysis, 62, 168-176. http://dx.doi.org/10.1016/j.jfca.2017.06.001
    » http://dx.doi.org/10.1016/j.jfca.2017.06.001

Publication Dates

  • Publication in this collection
    07 Jan 2022
  • Date of issue
    2022

History

  • Received
    17 Apr 2021
  • Accepted
    16 Nov 2021
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