Characterization and Comparison of Volatile Compounds of Cage, Organic and Free-Range Systems EggsABSTRACT
Studies on consumer preferences show that eggs obtained in open areas such as free-range systems and organic systems have superior taste than cage chicken eggs. Moreover, it is emphasized that the odor characteristics of eggs obtained in different production systems are different, and this reveals the necessity of determining the relevant volatile compounds. This study aimed to characterize and compare the volatile compounds responsible for the taste and aroma of eggs obtained from cage, organic and free-range systems. 60 randomly selected eggs (20 from each group sample) were analyzed by the SPME-GC-MS device. Eight volatile compounds were detected in the free-range chicken eggs, 15 in the caged chicken eggs, and 11 in the organic chicken eggs. D-limonene and 2-Butanamine, 3,3-dimethyl- compounds were determined as the main volatile odor components in all three groups of chicken eggs. Alkanes, esters, amines, acids, alcohols, ketones, aldehydes and alkenes were determined among the volatile compound groups. Acid and aldehyde groups of volatile compounds were not detected in the free-range and organic chicken eggs, as well as the ester group in free-range chicken eggs. In this study, both volatile compound numbers and compound groups of eggs belonging to different production systems were found to be different. This causes the eggs to differ in taste and aroma.
Keywords:
Cage systems; Free-range systems; Odor compounds; Organic systems; SPME-GC-MS
INTRODUCTION
Poultry eggs are an excellent food source for humans, as they contain many nutrients such as proteins, fats, vitamins, minerals, and growth factors (Wang et al., 2014). For this reason, egg quality and content are on the agenda of both breeders and consumers, being continuously studied from different perspectives. In addition to these nutrients detected in eggs, special compounds responsible for the characteristic egg aroma and odor have also been determined by some researchers. Matiella & Hsieh (1991) identified thirty-eight compounds, including aldehydes, ketones, alcohols, furans, esters, benzene derivatives, alkanes, sulfur-containing compounds and a terpene. Warren et al. (1995) also found that sulfur and sweet notes were sensory characteristics that differed between samples with varying yolk-white ratios.
In recent years, both nutritional value and odor characteristics of eggs obtained in different production systems have become important research subjects. Küçükyılmaz et al. (2012) detected that the P and Zn contents of the edible part of eggs were lower in organic eggs. Moreover, the Mg content of the eggshell was higher and there was a significant decrease in the Zn content. They did not see any differences between eggs in both systems for Ca, Fe, and Cu values. Mugnai et al. (2013) observed that organic system eggs showed lower concentrations of polyunsaturated fatty acids (PUFA) n-6 and a higher percentage of PUFA n-3. Wang et al. (2014) noticed that the volatile components of seven different species (duck, free-range chicken, silky chicken, quail, pigeon, goose, and chicken) egg yolks included nitrogenous compounds, alcohols, esters, and alkenes. The main substances that helped to distinguish between the various egg species were 1-butanol, N-isopropylbenzamide, methylisourea hydrogen sulfate, pathalic acid butyl isohexyl ester, and ethyl acetate.
The most common system used in commercial egg production in the world is the conventional cage system. It is a system in which high-yielding hybrids are housed indoors, under artificial lighting and ventilation conditions, where more than one animal is housed in cages and fed with commercial feeds (Matt et al., 2011). It is considered advantageous due to its high productive capacity.
In recent years, alternative systems such as enriched or furnished cage systems, free-range systems, and organic systems have been developed as a result of the prohibition of the conventional cage system, as it would adversely affect animal welfare and would not satisfy the physiological and behavioral needs of chickens. Among these alternatives, the free-range system provides shelter for the animals at night in a closed shelter, while offering the possibility of going out for 8 hours a day during the day and roaming freely in a green area (Sarıca, 2017). Animals can thus manifest their natural behavior and benefit from the sun in the open air (Baykalır & Şimşek, 2014). Another alternative is the organic system, in which animals are supplied from organic farms, fed with completely organic feeds, are genetically unaltered, resistant to the environment, climatic conditions and diseases, and mostly used of indigenous or local breeds of animals. There are green areas with a maximum of 4 chickens per m², and animals can roam freely in the open area (Organic Agriculture Regulation, 2010). The difference from the free-range system is that it is controlled, certified, and completely organic. In recent years, although consumer preferences have rapidly shifted towards products produced more naturally as a result of increased awareness about animal welfare and the consumption of healthy products, the cage system is still widely used in the United States, Turkey, and developing countries in general (Bertechini, 2017; Sarıca, 2017). Studies have emphasized that the odor characteristics of eggs obtained in different production systems are also different (Küçükyılmaz et al., 2012; Mugnai et al., 2013; Wang et al., 2014), and this suggests that the fatty acid profile and the identification of volatile compounds may differ. Studies on consumer preference show that eggs obtained in free-range systems have better taste than cage chicken eggs.
The belief that eggs produced in free-range and organic systems are more natural, safe, healthy, nutritious, high quality, tasty, nature and animal-friendly are the factors affecting consumer preference (Young et al., 2005; Pellegrini & Farinello, 2009; Celik, 2013; Pettersson et al., 2016; Baba et al., 2017; Zakowska-Biemans & Tekien, 2017; Bray & Ankeny, 2017; Karaalp et al., 2017; Güney & Giraldo, 2019). Features such as taste, aroma and smell, depending on production methods, appear as sub-factors that affect consumers’ egg preferences (Rondoni et al., 2020). A study reported that 87.9% of its participants consumed organic products, and 62.1% of them first paid attention to the fact that they were hormone-free when purchasing organic products, and 14.8% of them gave importance to their taste (Merdan, 2018).
The determination of which volatile compounds are related to the egg flavor preferred by the consumers is made using different instrumental analysis methods, and these analyses help to identify the flavor compounds (Mahmud et al., 2020). The GC-MS method used for the characterization of volatile profiles is widely used to determine odor properties (Capone et al., 2013; Cheng et al., 2013). In egg products, GC-MS has also been used to identify strong odors in heated egg yolks (Agozzino et al., 2005), cooked eggs (Cerny & Guntz, 2004), and spray-dried egg powders (Goldberg et al., 2012). However, there are few studies on the volatile aroma compounds of raw eggs. Therefore, this study aimed to examine the volatile compounds of raw eggs from different production systems (cage, organic, and free-range).
MATERIALS AND METHODS
Egg Samples
A total of 90 chicken eggs belonging to different production systems (30 from cages, 30 from free-range and 30 from organic systems) were purchased from the market in Adana province, in Turkey. A total of 60 egg samples (20 from each group) were randomly selected for analysis, after separating broken, dirty and cracked ones. Egg samples were carefully washed with 75% ethanol, dried at room temperature, and stored in a refrigerator at +4 °C until analysis in the laboratory. They were subsequently taken out of the refrigerator on the day of analysis, broken, and mixed homogeneously with the help of a beater, thus being ready for analysis in the GC-MS device.
Analysis of egg volatiles
Volatile compound analyses were performed at Çukurova University - Central Research Laboratory in 2021. Volatile component analysis was determined by the Agilent Brand 7890B GC, 7010B MS system. With the Solid Phase Micro-Extraction (SPME) method, 3 g of sample was placed in 20 mL vials and kept at 38 °C for 45 minutes. Then, the volatile components were absorbed for 30 minutes with a Solid Phase Micro Extraction (SPME) apparatus 50/30 µm Divinylbenzene / Carboxene / Polydimethylsiloxane coated fiber. Then, DB-Wax (60 m x 0.25mm i.dx 0.25 μm, J&W Scientific-Folsom, USA) was injected into the capillary column by desorbing for 5 minutes. After the injection temperature was kept at 250 °C and the column temperature at 40 °C for 4 minutes, it was increased to 90 °C by increasing 3 °C per minute, and then to 130 °C by increasing 4 °C per minute. After waiting for 4 minutes at this temperature, the temperature was adjusted to 240 °C by increasing 5 °C per minute, and kept at this temperature for 8 minutes. Helium was used as the carrier gas. The electron energy is 70 eV, and the mass range is 30-600 m/z. The split ratio is 1:10.
Identification of the volatile components was performed by comparing the mass spectra obtained with the NIST 11 massspectral library and identifications. The content or intensity of volatile components was semi-quantified by peak areas in the total ion chromatogram.
Statistical analysis
The experimental data were analyzed using SPSS 17.0, and results are presented as the mean ± standard error of the mean. A comparison of the volatile compounds found in eggs of different production systems (cage, organic and free-range) was made using analysis of variance (ANOVA), followed by Tukey’s test.
RESULTS
Retention time, molecular weight, odor descriptions, formula, CAS number, and function of volatile compounds detected by the SPME-GC-MS device in the eggs of different production systems (cage, organic and free-range) are given in Table 1, Table 2, and Table 3.
It was observed that the retention time of volatile compounds starts in 3.14, 3.13, 3.14 and ends in 34.62, 64.32, 64.35 minutes in the free-range, cage and organic system chicken eggs, respectively.
As a result of the analysis, eight volatile compounds were detected in free-range chicken eggs, 15 in caged chicken eggs, and 11 in organic chicken eggs (Table 4). The fact that both the peak number and % ratios of egg components of the three groups (free-range, cage and organic) defined in Table 4 were different suggests that the eggs may have their own odor, which may be due to the mixing of the compounds at certain rates in each group.
Hexane; Thieno[2,3-c]furan-3-carbonitrile, 2-amino-4,6-dihydro-4,4,6,6-tetramethyl-; 2-Butanamine, 3,3-dimethyl-; 2-Heptanol, 6-methyl-; decane; D-limonene and Acetamide, 2-fluoro- were volatile compounds commonly detected in all three groups of eggs (free-range, cage, and organic) (Table 4). As a result of the statistical analysis, only the differences between the groups of Hexane compounds were found to be significant (p<0.05) (Table 4). Although propane, 2-isocyanato, 2-Isononenal, Octanoic acid, n-Decanoic acid and Acetic acid, [(aminocarbonyl)amino] oxo- compounds were detected in cage eggs, they were not detected in either free-range or organic eggs. Similarly, Propanenitrile, 2-hydroxy and 4-occten-3-one/Methylpent-4-enylamine compounds were not observed in free-range eggs, but they were observed in the cage and organic eggs.
Another volatile compound of egg, Benzeneethanamine, .alpha.-methyl-, (S)-: was observed only in free-range eggs and not in cage eggs and organic chicken eggs. Similarly, Cyclohexanone/2-Propenoic acid, the ethenyl ester compound was only detected in organic chicken eggs. Compounds found in only one egg group and not the others can have an effect on the unique odor of that group (Xiang et al., 2018). D-limonene and 2-Butanamine, 3,3-dimethyl- compounds were determined as the main volatile odor components in all three production systems chicken eggs (cage, organic and free-range), contributing over 50% in total.
Total GC-MS ion chromatogram of volatiles from free-range (a), cage (b) and organic system (c) chicken eggs.
When the total ion chromatogram of all three production system eggs was examined in Figure 1, it was observed that the first retention time was the same, and the first peaks occured in the 3rd minute on average. However, it was observed that the peak time and peak number of volatile compounds were different in all three chicken eggs.
As a result of the analysis, alkanes, esters, amines, acids, alcohols, ketones, aldehydes and alkenes were determined from compound groups. While all groups were found in caged chicken eggs (Figure 2a), there are six groups in organic chicken eggs (Figure 2b) and five groups in free-range chicken eggs (Figure 2c).
The compound groups observed to have the highest ratio in free-range, cage and organic chicken eggs were respectively alkenes (45.29, 45.50, 32.17) and amines (26.66, 24.05, 26.36). As shown in Figures 2a, 2b and 2c, the ester, acid and aldehyde groups were not detected in free-range chicken eggs, and the acid and aldehyde volatile compounds groups were not present in organic chicken eggs. The common compound groups of all three system eggs were amine, alkane, alcohol, alkene and ketone groups (Figure 3).
The ratio of alkenes is quite high in all three groups (Figure 4). Although the ratio of alkenes in free-range and cage eggs were similar (average 45%), this ratio was lower in organic chicken eggs (approximately 32%).
DISCUSSION
In this study, 15 recognized compounds were observed in the cage system eggs analysis results (Table 4). Xiang et al. (2018) identified 17 or 18 volatile compounds in raw shell eggs in their study named characterization and classification of volatiles from different breeds of eggs by SPME-GC-MS and chemometrics. We identified fewer compounds than Xiang et al. (2018), but Hexane was reported in both Table 4 and that study. However, in Table 4, it is understood that the ratio of the Hexane compound is determined at a lower rate.
Plagemann et al. (2011) found less volatile compounds in eggs with free-range systems (control) compared to eggs with feed supplementation (onion, cabbage, rapeseed oil). Similar to the results of Plagemann et al. (2011), less volatile compounds were detected in the free-range chicken eggs in our study.
In this study, the Benzeneethanamine compound was found at a rate of 1.80%, only in free-range chicken eggs. Contrary to our study, Wang et al. (2014) detected the Benzeneethanamine compound in the egg yolk of seven different species (duck, free-range chicken, silken chicken, quail, pigeon, goose, and chicken). The same researchers also reported that Benzeneethanamine compound was present at a ratio of 3.67% in chicken eggs and 2.403% in free-range chicken eggs; thus identifying more Benzeneethanamine compounds as a percentage than us. When Table 4 was examined, no acid group compound was detected in free-range chicken eggs, similar to the study of Wang et al. (2014). In addition, more acid, less ester, alkene and ketone compounds were detected in cage chicken eggs than Wang et al. (2014) found.
The alkene group was identified as having the highest rate in this study (Table 4). Xiang et al. (2018) reported in their study that the compound with the highest ratio in white Leghorn, Hy-line brown and Jing fen chicken eggs was the aldehyde group. Additionally, in this study, aldehyde group compounds were identified only in the cage system eggs (2-Isononenal at a rate of 4.31%) and not in other systems eggs. Aldehydes can be products of sugar reduction or lipid oxidation, and their odor characteristics can range from pungent to oily (Chen & Ho, 1999). Except for lower carbon aldehydes, which have unpleasant odors, all other aldehydes and ketones generally have a pleasant odor. As the size of the aldehyde and ketone molecules increases, the odor becomes less pungent and more fragrant (Anonymous, 2023). Most esters have a non-specific fruity odor (Basear & Demirci, 2007). The eggs of free range chickens did not contain esters. Acids have an intense smell and sour taste (Schrader et al., 2004). Organic and free-range system eggs do not contain acid, so their taste may be softer.
The qualitative and quantitative compositions of volatile substances affect the quality of eggs and their taste, which is very important for consumers (Sansone-Land et al., 2014). The presence of volatile compounds in different ratios and groups in all three chicken eggs can cause differences in the flavor and quality of the eggs, as stated by Sansone-Land et al. (2014).
In some studies, it has been reported that there are differences in the internal and external quality of free-range and cage chicken eggs (Küçükkoyuncu et al., 2017), as well as their nutritional content. For example, vitamins and minerals are higher and cholesterol is lower in free-range chicken eggs (Brower et al., 2013). In this study, it was observed that the acid, ester and aldehyde group volatile compounds were determined in cage chicken eggs but not in free-range chicken eggs. This is an indication that the nutrient content of eggs with different production systems may be different, as well as the odor compounds.
Commercial feeds given to chickens in the cage system in order to maintain good health and quality production contain grains obtained from vegetable production and additives such as oilseeds, food industry by-products, oilseed meal, vitamins, minerals, probiotics, prebiotics, organic acids, enzymes, antimicrobial and antioxidant effective herbal extracts (Kutlu & Şahin, 2017; Mixed Feed Industry Report, 2019). These feeds contain all the nutrients that animals need, since the animals do not have the opportunity to get extra food from outside, as free-range and organic chickens. In Table 4, the fact that the number of compounds in the cage system is higher than that of free-range and organic chicken eggs may be due to feed additives.
Plageman et al. (2011) experimented with adding cabbage, onion and rapeseed to the feed of laying hens and found that it affected the aroma of eggs. Similarly, Hammershoj & Steenfelds (2012) investigated the effects on egg quality of kale, basil and thyme as feed material in organic egg production. As a result of the study, feed additives were found to affect egg flavor. These studies showed that the foods eaten by the animals affected egg contents, volatile compounds and, accordingly, flavor. In the cage system, the animals cannot eat anything other than the feed placed in front of them, while in the free-range and organic systems, they can roam freely in the open area and eat different plants, seeds and insects (Plageman et al., 2011; Hammershoj & Steenfelds, 2012). Therefore, it is estimated that the flavor difference between the eggs of these chickens is due to the volatile compounds they contain. When Table 4 is examined, the fact that the number of compounds and compound groups in the production systems is different supports this information.
CONCLUSIONS
As a result of the analyzes carried out to determine the volatile compounds in chicken eggs belonging to different production systems, eight volatile compounds were detected in free-range chicken eggs, 15 in caged chicken eggs, and 11 in organic chicken eggs. The most volatile compound groups (alkanes, esters, amines, acids, alcohols, ketones, aldehydes and alkenes) were observed in caged chicken eggs. Besides, ester, acid and aldehyde groups were not detected in free-range chicken eggs, and acid and aldehyde group volatile compounds also were not present in organic chicken eggs either.
The taste and quality of eggs, an important aspect in costumer preferences, is shaped by many factors. The brought-up conditions of the chickens, the feeds used, and the storage conditions affect the egg quality and cause differences. Within the scope of this study, the difference in the number of egg volatile compounds, % ratios, and compound groups in the three different production systems supports this claim.
ACKNOWLEDGMENTS
The author would like to thank Serap Goncu and Ozgul Anitas for their support.
REFERENCES
- Agozzino P, Avellone G, Ceraulo L, et al. Volatile profiles of Sicilian prickly pear (Opuntia ficus indica) by SPME-GC/MS analysis. Italian Journal of Food Science 2005;1:341-348.
-
Ataman Kimya-9759. D-limonene [cited 2023 May 2023]. Available from: https://atamankimya.com/sayfalar.asp?LanguageID=1&cid=3&id=9&id2=9759
» https://atamankimya.com/sayfalar.asp?LanguageID=1&cid=3&id=9&id2=9759 -
Baba Y, Kallas Z, Realini C. Application of the analytical hierarchy process to evaluate consumer acceptance and preferences for omega-3 enriched eggs. British Food Journal 2017;119(7):1459-72. https://doi.org/10.1108/BFJ-06-2016-0261
» https://doi.org/10.1108/BFJ-06-2016-0261 - Basear KHC, Demirci F. Chemistry of essential oil, in flavors and fragrances. Heidelberg: Springer; 2007. p.43-86.
- Baykalir Y, Simsek ÜG. Breeding systems used in laying hens. Firat University Journal of Health Science 2014;28:93-98.
- Bertechini AG. Economic and cultural aspects of the table egg as an edible commodity. In: Hester PY. Egg innovations and strategies for improvements. London: Elsevier; 2017. p.223-30. ISBN 978-0-12-800879-9
-
Bray HJ, Anken RA. Happy chickens lay tastier eggs: Motivations for buying free-range eggs in Australia. Anthrozoös 2017;30(2): 213-26. https://doi.org/10.1080/08927936.2017.1310986
» https://doi.org/10.1080/08927936.2017.1310986 - Brintha S, Rajesh S, Renuka R, et al. Phytochemical analysis and bioactivity prediction of compounds in methanolic extracts of Curculigo orchioides Gaertn. Journal of Pharmacognosy and Phytochemistry 2017;6(4):192-197.
-
Brower S, Dorsey J, Malvetti K, et al. Taste and nutritional differences of non-factory farmed vs. factory farmed eggs and poultry [cited 2023 Aug 11]. Available from: https://rucore.libraries.rutgers.edu/rutgerslib/45132/PDF/1/play/
» https://rucore.libraries.rutgers.edu/rutgerslib/45132/PDF/1/play -
Capone S, Tufariello M, Francioso L et al. Aroma analysis by GC/MS and electronic nose dedicated to Negroamaro and Primitivo typical Italian Apulian wines. Sensors and Actuators B: Chemical 2013;179:259-69. https://doi.org/10.1016/j.snb.2012.10.142
» https://doi.org/10.1016/j.snb.2012.10.142 - Celik S. Who and why buy organic food? A field research. The Journal of Selcuk University Social Sciences Institute 2013;30:93-108.
-
Cerny C, Guntz R. Evaluation of potent odorants in heated egg yolk by aroma extract dilution analysis. European Food Research and Technology 2004;219:452-4. https://doi.org/10.1007/s00217-004-1000-8
» https://doi.org/10.1007/s00217-004-1000-8 -
Chemical Book. Propanenitrile, 2-hydroxy [cited 2023 Oct. 2023]. Available from: https://www.chemicalbook.com/CASEN_78-97-7.htm
» https://www.chemicalbook.com/CASEN_78-97-7.htm -
Chen J, Ho CT. Volatile compounds identified in preserved duck eggs, In: Shahidi F, Ho CT. Flavor chemistry of ethnic foods. Boston: Springer; 1999 p.263-8 [cited 2023 Jun 7]. https://doi.org/10.1007/978-1-4615-4783-9_25
» https://doi.org/10.1007/978-1-4615-4783-9_25 -
Cheng H, Qin ZH, Guo XF, et al. Geographical origin identification of propolis using GC-MS and electronic nose combined with principal component analysis. Food Research International 2013;51:813-22. https://doi.org/10.1016/j.foodres.2013.01.053
» https://doi.org/10.1016/j.foodres.2013.01.053 -
CS-471596. Methylpent-4-enylamine [cited 2023 Oct 2]. Available from: http://www.chemspider.com/Chemical-Structure.471686.html
» http://www.chemspider.com/Chemical-Structure.471686.html - Diep CN, Phuong YV, Linh NTT, et al. The diversity and antimicrobial activity of endophyte fungi isolated from the sponge at NGHE Island, Ha Tien Sea, Kien Giang Province, Vietnam. Ecology Environment and Conservation 2021;27(3):1074-1087.
-
Goldberg E, Gakhar N, Ryland D, et al. Fatty acid profile and sensory characteristics of table eggs from laying hens fed hempseed and hempseed oil. Journal of Food Science 2012;77(4):153-60. https://doi.org/10.1111/j.1750-3841.2012.02626.x
» https://doi.org/10.1111/j.1750-3841.2012.02626.x -
Güney OI, Giraldo L. Consumers' attitudes and willingness to pay for organic eggs A discrete choice experiment study in Turkey. British Food Journal 2019;122(2):67892. https://doi.org/10.1108/BFJ-04-2019-0297
» https://doi.org/10.1108/BFJ-04-2019-0297 -
Hammershoj M, Steenfeldt, S. The effects of kale (Brassica oleracea ssp. acephala), basil (Ocimum basilicum) and thyme (Thymus vulgaris) as forage material in organic egg production on egg quality. British Poultry Science 2012;53(2):245-56. https://doi.org/10.1080/00071668.2012.681770
» https://doi.org/10.1080/00071668.2012.681770 -
Karaalp M, Kaya H, Aksakal, V. Improvement possibilities of some nutritional and sensory properties of organically produced laying hen eggs. Turkish Journal of Agriculture - Food Science and Technology 2017;5(13):1802-9. http://orcid.org/0000-0002-1794-031X
» http://orcid.org/0000-0002-1794-031X -
Küçükkoyuncu E, Okur AA, Tahtabicen E, et al. Comparing quality of free range and battery cage eggs. European Poultry Science 2017;81:197. https://doi.org/10.1399/eps.2017.197
» https://doi.org/10.1399/eps.2017.197 -
Küçükyilmaz K, Bozkurt M, Yamaner Ç, et al. Effect of an organic and conventional rearing system on the mineral content of hen eggs. Food Chemistry 2012;132:989-92. https://doi.org/10.1016/j.foodchem.2011.11.084
» https://doi.org/10.1016/j.foodchem.2011.11.084 -
Kutlu HR, Sahin A. Recent studies and recommendations for future in poultry nutrition. Journal of Animal Production 2017;58(2):66-79. https://doi.org/10.29185/hayuretim.333882
» https://doi.org/10.29185/hayuretim.333882 -
Mahmud MMC, Shellie RA, Keast R. Unravelling the relationship between aroma compounds and consumer acceptance: Coffee as an example. Comprehensive Reviews in Food Science and Food Safety 2020;19:2380-420. https://doi.org/10.1111/1541-4337.12595
» https://doi.org/10.1111/1541-4337.12595 -
Matiella E, Hsieh TCY. Volatile compounds in scrambled eggs. Journal of Food Science 1991;56:387-90. https://doi.org/10.1111/j.1365-2621.1991.tb05286.x
» https://doi.org/10.1111/j.1365-2621.1991.tb05286.x - Matt D, Rembialkowska E, Luik A, et al. Quality of organic vs. conventional food and effects on health report. Tartu: Estonian University of Life Sciences; 2011. ISBN 978-9949-484-06-5
-
Merdan K. Determining the level of information and perspective of university students regarding genetically modified (transgenic) products: Gumushane University sample. Journal of Ufuk University Institute of Social Sciences 2018;4(8):174-88. https://doi.org/ 10.22573/spg.ijals.017.s12200078
» https://doi.org/ - Mixed feed industry report. Turkish feed manufacturers association compound feed industry report. Ankara: Poyraz Ofset Printing; 2019.
-
Mugnai C, Sossidou EN, Dal Bosco A, et al. The effects of husbandry system on the grass intake and egg nutritive characteristics of laying hens. Journal of the Science of Food and Agriculture 2013;94(3):459-67. https://doi.org/10.1002/jsfa.6269
» https://doi.org/10.1002/jsfa.6269 -
National Center for Biotechnology Information [NCBI- CID379]. PubChem Compound Summary for CID 379, Octanoic acid [cited 2023 Sep 19]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/Octanoic-acid
» https://pubchem.ncbi.nlm.nih.gov/compound/Octanoic-acid -
National Center for Biotechnology Information [NCBI-CID11381345]. PubChem Compound Summary for CID 11381345, Cyclopropaneoctanoic acid, 2-octyl-, methyl ester, (1R,2S) [cited 2023 Sep 16]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/methyl-8-_1R_2S_-2-octylcyclopropyl_octanoate
» https://pubchem.ncbi.nlm.nih.gov/compound/methyl-8-_1R_2S_-2-octylcyclopropyl_octanoate -
National Center for Biotechnology Information (NCBI-CID12542]. PubChem Compound Summary for CID [12542, Fluoroacetamide. 2023 [cited 2023 Sept 30]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/Fluoroacetamide
» https://pubchem.ncbi.nlm.nih.gov/compound/Fluoroacetamide -
National Center for Biotechnology Information [NCBI-CID2969]. PubChem Compound Summary for CID 2969, Capric Acid [cited 2023 Oct 1]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/Capric-Acid
» https://pubchem.ncbi.nlm.nih.gov/compound/Capric-Acid -
National Center for Biotechnology Information [NCBI-CID456. PubChem Compound Summary for CID 456, Oxaluric acid [cited 2023 Oct 7]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/Oxaluric-acid
» https://pubchem.ncbi.nlm.nih.gov/compound/Oxaluric-acid -
National Center for Biotechnology Information [NCBI-CID5324845]. PubChem Compound Summary for CID 5324845, (2R)-3,3-dimethylbutan-2-amine [cited 2023 May 28]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/2R_-3_3-dimethylbutan-2-amine
» https://pubchem.ncbi.nlm.nih.gov/compound/2R_-3_3-dimethylbutan-2-amine -
National Center for Biotechnology Information [NCBI-CID5825]. PubChem Compound Summary for CID 5825, Dextroamphetamine sulfate [cited 2023 Oct 2]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/Dextroamphetamine-sulfate
» https://pubchem.ncbi.nlm.nih.gov/compound/Dextroamphetamine-sulfate -
National Center for Biotechnology Information [NCBI-CID61277]. PubChem Compound Summary for CID 61277, Isopropyl isocyanate [cited 2023 Nov 9]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/Isopropyl-isocyanate
» https://pubchem.ncbi.nlm.nih.gov/compound/Isopropyl-isocyanate -
National Center for Biotechnology Information [NCBI-CID8058]. PubChem Compound Summary for CID 8058, n-HEXANE [cited 2023 Sep 1]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/n-HEXANE
» https://pubchem.ncbi.nlm.nih.gov/compound/n-HEXANE -
National Center for Biotechnology Information [NCBI-CID87291600]. PubChem Compound Summary for CID 87291600, 2-Isononenal [cited 2023 May 18]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/2-Isononenal
» https://pubchem.ncbi.nlm.nih.gov/compound/2-Isononenal -
National Center for Biotechnology Information [NCBI-CID96476]. PubChem Compound Summary for CID 96476, 6-Methyl-2-heptanol [cited 2023 Sep 29]. Available online: https://pubchem.ncbi.nlm.nih.gov/compound/6-Methyl-2-heptanol
» https://pubchem.ncbi.nlm.nih.gov/compound/6-Methyl-2-heptanol - Organic Agriculture Regulation. Regulation on the principles and practice of organic agriculture, Official Gazette 2010;(27676).
-
Pellegrini G, Farinello F. Organic consumers and new lifestyles an Italian country survey on consumption patterns. British Food Journal 2009;111(9):948-74. https://doi.org/10.1108/00070700910992862
» https://doi.org/10.1108/00070700910992862 -
Pettersson IC, Weeks CA, Wilson LRM, et al. Consumer perceptions of free-range laying hen welfare. British Food Journal 2016;118:1999-2013. https://doi.org/10.1108/BFJ-02-2016-0065
» https://doi.org/10.1108/BFJ-02-2016-0065 -
Physical properties of aldehydes and ketones [cited 2023 Apr 11]. Available from: https://www.perfumelounge.eu/fragrance-notes/aldehydes
» https://www.perfumelounge.eu/fragrance-notes/aldehydes -
Plagemann I, Zelena K, Krings U, et al. Volatile flavours in raw egg yolk of hens fed on different diets. Journal of the Science of Food and Agriculture 2011;91(11):2061-5. https://doi.org/10.1002/jsfa.4420
» https://doi.org/10.1002/jsfa.4420 -
Rondoni A, Asioli D, Millan E. Consumer behaviour, perceptions, and preferences towards eggs: A review of the literature and discussion of industry implications. Trends in Food Science and Technology 2020;106:391-401. https://doi.org/10.1016/j.tifs.2020.10.038
» https://doi.org/10.1016/j.tifs.2020.10.038 -
RW1586051. 4-occten-3-one [cited 2023 Oct 5]. Available from: http://www.thegoodscentscompany.com/data/rw1586051.html
» http://www.thegoodscentscompany.com/data/rw1586051.html -
Sansone-Land A, Takeoka GR, Shoemaker C F. Volatile constituents of commercial imported and domestic black-ripe table olives (Olea europaea). Food Chemistry 2014;149:285-95. https://doi.org/10.1016/j.foodchem.2013.10.090
» https://doi.org/10.1016/j.foodchem.2013.10.090 - Sarica M. Comparison of alternative egg production systems. 3th ed. Antalya: Egg Summit; 2017. p.41-50.
-
Schrader J, Etschmann MMW, Sell D, et al. Applied biocatalysis for the synthesis of natural flavour compounds - current industrial processes and future prospects. Biotechnology Letters 2004;26:463-72. https://doi.org/10.1023/B:BILE.0000019576.80594.0e
» https://doi.org/10.1023/B:BILE.0000019576.80594.0e -
TFE - The Free Encyclopedia. Decane; 2023a [cited 2023 oct 6]. Available from: https://en.wikipedia.org/wiki/Decane
» https://en.wikipedia.org/wiki/Decane -
TFE - The Free Encyclopedia. Cyclohexanone; 2023b [cited 2023 oct 13]. Available from,: https://en.wikipedia.org/wiki/Cyclohexanone
» https://en.wikipedia.org/wiki/Cyclohexanone -
TFE - The Free Encyclopedia. Vinyl acrylate; 2023c [cited 2023 oct 5]. Available from: https://eo.wikipedia.org/wiki/Vinila_akrilato
» https://eo.wikipedia.org/wiki/Vinila_akrilato -
Valduga E, Valério A, Treichel H, et al. Head Space Solid Phase Micro-Extraction (HS - SPME) of volatile organic compounds produced by Sporidiobolus salmonicolor (CBS 2636). Food Science and Technology 2010;30(4):987-92. https://doi.org/10.1590/S0101-20612010000400023
» https://doi.org/10.1590/S0101-20612010000400023 -
Wang Q, Jin G, Jin Y, et al. Discriminating eggs from different poultry species by fatty acids and volatiles profiling: Comparison of SPME-GC/MS, electronic nose, and principal component analysis method. European Journal of Lipid Science and Technology 2014;116(8):1044-53. https://doi.org/10.1002/ejlt.201400016
» https://doi.org/10.1002/ejlt.201400016 -
Warren M, Larick DK, Ball Jr, HH. Volatile and sensory characteristics of cooked egg yolk, white and their combinations. Journal of Food Science 1995;60:79-83. https://doi.org/10.1111/j.1365-2621.1995.tb05611.x
» https://doi.org/10.1111/j.1365-2621.1995.tb05611.x -
Xiang X, Jin G, Gouda M, et al. Characterization and classification of volatiles from different breeds of eggs by SPME-GC-MS and chemometrics. Food Research International 2018;116:767-77. https://doi.org/10.1016/j.foodres.2018.09.010
» https://doi.org/10.1016/j.foodres.2018.09.010 -
Young JE, Zhao X, Carey E, et al. Phytochemical phenolics in organically grown vegetables. Molecular Nutrition and Food Research 2005;49:1130-42. https://doi.org/10.1002/mnfr.200500080
» https://doi.org/10.1002/mnfr.200500080 -
Zakowska-Biemans S, Tekien A. Free range, organic? Polish consumers preferences regarding information on farming system and nutritional enhancement of eggs: a discrete choice-based experiment. Sustainability 2017;9(11):1-16. https://doi.org/10.3390/su9111999
» https://doi.org/10.3390/su9111999
-
Data availability statement
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Disclaimer/Publisher’s Note
The published papers’ statements, opinions, and data are those of the individual author(s) and contributor(s). The editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content.
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Publication Dates
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Publication in this collection
01 Nov 2024 -
Date of issue
2024
History
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Received
28 Oct 2023 -
Accepted
18 June 2024
