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Effect of Different Thermal and Non-Thermal Processing Methods on Chemical Composition, Quality Indicators and Apparent Nutrient Digestibility of Full-Fat Soybean

ABSTRACT

The aim of this research was to study the effect of thermal and non-thermal processing methods on chemical composition, quality indicators and apparent digestibility of soybean nutrients. For this, four processing methods (unprocessed, extruded, thermal, and gamma radiation) were applied on two soybean varieties (Katol & Caspian). Rations were formulated based on kinds of soybean (processed and unprocessed). The experiment was continued using 600 male Ross broiler chickens during 3 feeding phases (starter, grower, and finisher). Traits were measured and analyzed with the Lsmeans procedure by SAS software. The results showed the interaction effects of soybean varieties and processing methods were significant on the crude fiber, calcium, and phosphorus (p<0.05). The effect of soybean variety was significant on the crude protein, crude fiber, and phosphorus (p<0.05). Also, the effect of processing methods was significant on the dry matter, crude fiber, and phosphorus (p<0.05). The effect of soybean variety, processing methods, and their interaction were significant on urease activity, KOH protein solubility, and Protein dispersibility index (p<0.05). The results of the current study showed that the best soybean variety and the processing method is the Caspian and thermal, respectively.

Keywords:
Digestibility; Processing; Soybean; Thermal; Varieties

INTRODUCTION

The world production of processed feed is about one billion tons per year. A large part of the feed is processed in a form or another. Furthermore, even if the complete feed is not produced, many feed components are processed using feed processing techniques before the feed is consumed. As a result, the feed processing effect on the feed nutritional value is important to take into consideration. Before the particle size reduction and digestibility of feed ingredients increase, they are ground (Wondra et al., 1995Wondra KJ, Hancock JD, Behnke KC, Hines RH, Stark CR. Effects of particle size and pelleting on growth performance, nutrient digestibility, and stomach morphology in finishing pigs. Journal of Animal Science 1995;73(3):757-763.). Also, maybe feed ingredients are processed by thermal method to reduce the effect of the anti-nutritional factors, but heating effects on energy and nutrient digestibility may be negative or positive (Herkelman et al., 1992Herkelman KL, Cromwell GL, Stahly TS, Pfeiffer TW, Knabe DA. Apparent digestibility of amino acids in raw and heated conventional and low-trypsin-inhibitor soybeans for pigs. Journal of Animal Science 1992;70(3):818-826.). Examples of processing techniques include expander processing, pelleting, and extrusion (Lundblad et al., 2011Lundblad KK, Issa S, Hancock JD, Behnke KC, McKinney LJ, Alavi S, et al. Effects of steam conditioning at low and high temperature, expander conditioning and extruder processing prior to pelleting on growth performance and nutrient digestibility in nursery pigs and broiler chickens. Animal Feed Science and Technology 2011;169(3-4):208-217.). The soybean is by far the most important oilseed crop in the world. Its crude protein content with the high content of essential amino acids and the oil content is 38% and 18%, respectively. Also, the fiber content of soybean is low. Soybean is used as a protein source in animal feed (Garnsworthy and Wiseman, 2009Garnsworthy PC, Wiseman J. Recent advances in animal nutrition 2008. Nottingham: Nottingham University Press; 2009.). If the soybean oil is not extracted, it is known as full-fat soybean. There are important points in the use of full-fat soybeans in chicken rations. Other than eliminating the oil extraction cost, the high-energy rations can be formulated (Simovic et al., 1972Simovic R, Bilanski W, Summers J. Heat treatment of full-fat soybeans. Canadian Journal of Animal Science 1972;52(1):183-188.).

The use of raw soybeans in chicken rations was limited by the presence of heat-labile trypsin inhibitors and other anti-nutritional factors (Offiong, 1984Offiong SA. Evaluation of the nutritive value of full-fat soybean for chickens [thesis]. Zaria, (NGR): Department of Animal Science, Ahmadu Bello University;1984.). These factors make growth depression and pancreatic hypertrophy in many animals (Birk, 1988). It was shown that growth depression is caused by the combined effect of essential amino acids loss (especially amino acids contained sulfur) and decreased intestinal proteolysis (caused by trypsin inhibitors) in raw soybeans (Tan-Wilson & Wilson, 1986Tan-Wilson AL, Wilson KA. Relevance of multiple soybean trypsin inhibitor forms to nutritional quality. In: Friedman M., editor. Nutritional and toxicological significance of enzyme inhibitors in foods. Boston: Springer; 1986. p.391-411.). To improve the nutritional value of full-fat, soybean should be treated by heat before using it in the chicken ration. Some of the heat processing methods of full-fat soybean are extrusion, micronization, and jet Sploding (Marty & Chavez, 1993Marty BJ, Chavez ER. Effects of heat processing on digestible energy and other nutrient digestibilities of full-fat soybeans fed to weaner, grower and finisher pigs. Canadian Journal of Animal Science 1993;73(2):411-419.). Researchers documented that with the increase in the cooking duration of soybean, apparent digestibility and retention of dietary dry matter, nitrogen, and ether extract increased (Vandergrift et al., 1983Vandergrift WL, Knabe DA, Tanksley Jr TD, Anderson SA. Digestibility of nutrients in raw and heated soyflakes for pigs. Journal of Animal Science 1983;57(5):1215-1224..; Balloun, 1980Balloun SL. Soybean meal in poultry nutrition. Sainnt Louis: American Soybean Association; 1980.; and Kaankuka et al., 1996Kaankuka FG, Balogun TF, Tegbe TSB. Effects of duration of cooking of full-fat soya beans on proximate analysis, levels of antinutritional factors, and digestibility by weanling pigs. Animal Feed Science and Technology 1996;62(2-4):229-237.). A study reported that ileal digestibility of dry matter, gross energy, and nitrogen were greatest and lowest for extruded and roasted soybean, respectively (Kim et al., 2000Kim IH, Hancock JD, Hines RH. Influence of processing method on ileal digestibility of nutrients from soybeans in growing and finishing pigs. Asian-Australasian Journal of Animal Sciences 2000;13(2):192-199.). The nutritional quality of soybean can be increased by processing methods of toasting, cooking, extruding, salt treatment, fermentation, germination pressure cooking, cooking, soaking, and urea treatment (Akande & Fabiyi, 2010Akande KE, Fabiyi EF. Effect of processing methods on some antinutritional factors in legume seeds for poultry feeding. International Journal of Poultry Science 2010;9(10):996-1001.; Milczarek et al., 2017Milczarek A, Osek M, Kwiecien M, Pachnik M. Influence of raw or extruded soybean seeds in broiler chicken mixtures on rearing parameters, slaughter value and liver histological image. Medycyna Weterynaryjna 2017;73(12):764-769.).

Therefore, this study aimed to investigate the effect of different thermal and non-thermal processing methods on chemical composition, quality indicators and apparent digestibility of nutrients of soybean.

MATERIALS AND METHODS

Chicken

In the present study, 600 male broiler chickens of Ross 308 were randomly distributed into 8 treatments with 5 replicates per treatment, in a total of 15 birds per treatment. The experiment started with one-day-old chicks, which were randomly assigned into groups with similar mean body weights, with a starting average weight of 42 g. The experimental rations were maintained until the age of 42 days. Birds were given ad libitum access to water and feed. The chickens were fed the isocaloric and isonitrogenous starter, grower and finisher rations formulated according to Aviagen recommendations for Ross 308 broiler chickens. The basal ration is presented in table 1. The amount used of processed and unprocessed soybean varieties in the starter, grower, and finisher rations were 5, 10 and 15%, respectively. In each ration, soybean meal is replaced with the full-fat soybean.

Table 1
Composition of starter, grower and finisher rations (%).

Processing methods of soybean rations

All thermal and non-thermal processing was performed at the Nutrition Laboratory of the agriculture faculty of Islamic Azad University, Qaemshahr Branch. For the heat processing, samples of 1.5 kg were placed into the center of trays and then distributed homogeneously over the tray’s surface to achieve uniformity during treatment. After the thermal processing, the soybean was cooled in a different tray. Then, it was transferred into plastic bags and stored at a suitable temperature (25ºC, 60% humidity). In this experiment two soybean varieties were used (Katol & Caspian). The soybean samples were wet extruded at 145, 155 and 165°C for 15s by an extruder system (Yemmak Co. Turkey). Soybean seeds were irradiated with the 1, 2, 4, and 10 kGy doses of gamma radiation. The dose rate was 228Gy/min (Štajner et al., 2007Štajner D, Milošević M, Popović BM. Irradiation effects on phenolic content, lipid and protein oxidation and scavenger ability of soybean seeds. International Journal of Molecular Sciences 2007;8(7):618-627.).

Apparent nutrient digestibility

On day 15 a digestibility trial was carried out on the chickens. Weighed quantities of rations were supplied, and excreta were collected over 72 h in plastic sheeting placed under the wire mesh of the cage by the total collection method. Excreta samples were oven dried (70ºC for 20 h), weighed, ground and stored in airtight Kilner jars (Apata, 2008Apata DF. Growth performance, nutrient digestibility and immune response of broiler chicks fed diets supplemented with a culture of Lactobacillus bulgaricus. Journal of the Science of Food and Agriculture 2008;88(7):1253-1258.). Duplicate samples of rations and dried excreta were analyzed for proximate components using Association of official analytical chemists (1990) methods. Then, the values were used to compute apparent nutrient digestibility (such as dry matter, crude ash, crude fat, crude fiber, and crude protein).

With the combination of factors’ levels under study, eight treatments were studied as follows:

1) control, un-processed soybean with Katol soybean, 2) extruded soybean with Katol soybean, 3) thermal soybean with Katol soybean, 4) gamma soybean with Katol soybean, 5) control, un-processed soybean with Caspian soybean, 6) Extruded soybean with Caspian soybean, T) thermal soybean with Caspian soybean and 8) Gamma soybean with Caspian soybean.

Quality indicators

Urease activity was determined according to the AOCS (1997) official procedure. Two hundred milligrams of full-fat soybean sample was incubated in 10.0 ml of phosphate buffered urea solution at 300 C for 30 minutes, after which the increase in pH was recorded from 7.00.

KOH protein solubility determination

Protein solubility was determined in potassium hydroxide as follows: 1.5 g (± .001 g) of a full-fat soybean sample, ground in a Udy mill (Udy Corporation, Boulder, CO), so it would pass through a 0.5 mm screen, mixed with 75 ml of 0.2% (0.036 normal, pH= 12.5) potassium hydroxide, then stirred for 20 min on a magnetic plate. The mixture was centrifuged at 2700 rpm for 15 min. The supernatant was decanted, avoiding centrifugation, and filtered through glass wool. About 40 mL were recovered in a 50 mL beaker. Fifteen milliliters, in duplicate from a single filtrate, was transferred to Kjeldahl tubes giving a 0.3-g aliquot of the original sample (1.5 g x 15 mL per 75 ml). Twelve-and-a-half ml of concentrated H2SO4, 2 Kjeltabs, and 2 ml of 30 % H2O2 were added to each tube. Total nitrogen was determined by the Kjeldahl method, and the protein content was calculated. For the original samples, the crude protein content was also determined. Protein solubility was determined as a percentage of the total protein soluble in the 2 % solution of potassium hydroxide (Araba & Dale, 1990Araba M, Dale NM. Evaluation of protein solubility as an indicator of overprocessing soybean meal. Poultry Science 1990;69(1):76-83.).

Protein dispersibility index (PDI) determination

The PDI for the full-fat soybean was determined according to method AOCS (1997). For this, a 20 g sample was weighed, and processed for 10 min at 8500 rpm in distilled water (pH= 7.0) at 25°C. The mixture was centrifuged for 10 min at 1400 rpm and room temperature (24°C), and the supernatant nitrogen was determined. Results were expressed as the percentage of dispersible protein respect to the protein content of the original sample.

Statistical analysis

The main and interactions effects of the soybean varieties (Katol and Caspian) and its processing methods (unprocessed, extruded, thermal, and gamma radiation) were studied in a 2×4 factorial experiment in form of completely randomized design. Data analysis was done with the Lsmeans procedure by SAS package (2001).

The statistical model was as follows:

y i j k = µ + A i + B j + ( A B ) i j + e i j k

Where yijk= the value of each observation, µ= mean effect, Ai= effect of soybean varieties (Katol and Caspian), Bj= processing methods of soybean (unprocessed, extruded, thermal, and gamma radiation), (AB)ij= interaction effect of soybean varieties and processing methods of soybean, and eijk= residual effects.

RESULTS AND DISCUSSION

As shown in table 2, the effect of soybean variety was significant on crude protein, crude fiber, and phosphorus (p<0.01). Also, the effect of processing methods was significant on dry matter, crude fiber, and phosphorus (p<0.01). The interaction effect of soybean variety and processing methods was significant on crude fiber, calcium, and phosphorus (p<0.05). The highest and the lowest amount of crude fiber were in Katol soybean without processing and extruded Caspian soybean, respectively. The highest and lowest calcium was in thermal Katol soybean and extruded Caspian soybean respectively. The highest and lowest phosphorus was in thermal Caspian soybean and extruded Katol soybean respectively. In soybean variety, the highest and the lowest crude protein and phosphorus content were found in Caspian and Ketal, and the highest and lowest amount of raw fiber was found in Katol and Caspian, respectively. The highest and the lowest amount of dry matter and phosphorus were observed in thermal processing and gamma as well as the highest and the lowest crude fiber, respectively, without processing and heat treatment, respectively. Results of Maidala et al. (2013Maidala A, Udoma UD, Egbo LM. Effects of different processing methods on the chemical composition and antinutritional factors of soybean [Glycine max (L.) Merrill]. Pakistani Journal of Nutrition 2013;12(12):1057-1060.) and Milczarek et al. (2017Milczarek A, Osek M, Kwiecien M, Pachnik M. Influence of raw or extruded soybean seeds in broiler chicken mixtures on rearing parameters, slaughter value and liver histological image. Medycyna Weterynaryjna 2017;73(12):764-769.) showed in their studies that there was an increase in crude protein, crude fiber and crude fat of differently processed soybeans. There was a decrease in the nitrogen-free extract, calcium, and phosphorus of differently processed soybean. The chemical compositions and functional properties of the full-fat soybean were influenced by processing and soybean variety. Suitable processing techniques may enhance the utilization of soybean (Ukwuru, 2003Ukwuru MU. Effect of processing on the chemical qualities and functional properties of soy flour. Plant Foods for Human Nutrition 2003;58(3):1-11.). When comparing Full-fat soybean (FFSB) with the extruded FFSB product, it seems likely that the high residence time during micronization in combination with the lack of any extra moisture may have resulted in more severe destruction of protein as expressed by the lower available lysine (Zarkadas & Wiseman, 2005Zarkadas LN, Wiseman J. Influence of processing of full fat soya beans included in diets for piglets:II. Digestibility and intestinal morphology. Animal Feed Science and Technology 2005;118(1-2):121-137.).

Table 2
Effect of experimental treatments on chemical composition of ration’s soybean (%).

The effect of processing methods was significant on apparent nutrient digestibility factors such as crude protein, ether extract, and ash (p<0.05) (Table 3). Interaction effect of soybean variety and processing methods was significant on dry matter, crude protein, and ether extract (p<0.05) (Table 3). The results of a study on broiler chickens showed that the apparent digestibility of nutrients was affected by the dietary treatments in raw and roasted soybeans (Rocha et al., 2014Rocha C, Durau JF, Barrilli LNE, Dahlke F, Maiorka P. The effect of raw and roasted soybeans on intestinal health, diet digestibility, and pancreas weight of broilers. Journal of Applied Poultry Research 2014;23(1):71-79.), that was consistent with the results of this study. Parsons et al. (1992Parsons CM, Hashimoto K, Wedekind KJ, Han Y, Baker DH. Effect of overprocessing on availability of amino acids and energy in soybean meal. Poultry Science 1992;71(1):133-140.) evaluated the effects of over-heating on the availability of soybean meal amino acids in broilers and found that the true digestibility of several amino acids decreased as autoclaving time increased from 0 to 40 min. In a study, digestibility of dry matter, Neutral Detergent Fiber (NDF), and crude protein did not differ in ground soybean and roasted soybean (Andrade et al., 2015Andrade VR, Leonel FDP, Villela SDJ, Carvalho JDC, Araújo RP, Carvalho JMD, et al. JT. Soybean in different forms of processing in the feeding of crossbred cows on brachiaria grass pastures. Revista Brasileira de Zootecnia 2015;44(2):37-43.). Zhang et al. (1993Zhang YE, Parsons CM, Weingartner KE, Wijeratne WB. Effects of extrusion and expelling on the nutritional quality of conventional and Kunitz trypsin inhibitor-free soybeans. Poultry Science 1993;72(12):2299-2308.) reported that extruding significantly increases the digestibility of soybeans. Lichovnikova et al. (2004Lichovnikova M, Zeman L, Kracmar S, Klecker D. The effect of the extrusion process on the digestibility of feed given to laying hens. Animal Feed Science and Technology 2004;116(3-4):313-318.) showed that extrusion processing significantly increased the apparent digestibility of crude fat and crude protein in the poultry. Extrusion can not only reduce anti-nutrients in full-fat soybean to a large extent, but also, using the high pressure it produces, can pressure the seed and, by breaking down, digestible nutrients, and the metabolizable energy of the seeds to improve (Perilla et al., 1997Perilla NS, Cruz MP, De Belalcazar F, Diaz GD. Effect of temperature of wet extrusion on the nutritional value of full-fat soyabeans for broiler chickens. British Poultry Science 1997;38(4):412-416.). In general, heating improves the digestibility of proteins by inactivating enzyme inhibitors and denaturing the protein that may expose new sites for enzyme attack (Camire et al., 1990Camire ME, Camire A, Krumhar K. Chemical and nutritional changes in foods during extrusion. Critical Reviews in Food Science & Nutrition 1990;29(1):35-57.). Danicke et al. (1998Danicke S, Kracht W, Jeroch H, Zachmann R, Heidenreich E, Löwe R. Effect of different technical treatments of rapeseed on the feed value for broilers and laying hens. Archives of Animal Nutrition 1998;51(1):53-62.) found that increasing the temperature of the thermal treatments resulted in an increase in crude fat digestibility. Dahlin and Lorenz (1993Dahlin K, Lorenz K. Protein digestibility of extruded cereal grains. Food Chemistry 1993;48(1):13-18.) observed a beneficial effect of extrusion on protein digestibility of cereal-grain in vitro. The result of a study showed that roasted full-fat soybeans had no effect on nutrient digestibility of dry matter. crude protein, and crude fiber, which was consistent with the results of this study (Hamilton & McNiven, 2000Hamilton RM, McNiven MA. Replacement of soybean meal with roasted full-fat soybeans from high-protein or conventional cultivars in diets for broiler chickens. Canadian Journal of Animal Science 2000;80(3):483-488.).

Table 3
Effect of experimental treatments on apparent nutrient digestibility of soybean (%).

The effect of soybean variety, processing methods, and interaction of them were significant on urease activity, KOH protein solubility, and protein dispersibility index (p<0.05) (Table4). Protein quality indicators show that some of the samples may be over-processed or less processed. According to Batal et al. (2000Batal AB, Douglas MW, Engram AE, Parsons CM. Protein dispersibility index as an indicator of adequately processed soybean meal. Poultry Science 2000;79(11):1592-1596.), the protein differentiation index (PDI) of 45% for soybeans is suitable for thermal processing, which results in good growth performance in broiler chickens. Batal and et al. (2000) reported that the PDI index was an appropriate response to heat soybean, while Dudley-Kash (2001) stated that the PDI index could show better soybean quality than other indicators.

Table 4
Effect of experimental treatments on quality indicators of soybean.

In conclusion, the thermal method and the use of soybean Caspian improved the quality indicators of soybean measured in this study. The apparent digestibility of dry matter, crude protein and crude fiber in the extruded process showed better results. The thermal processing in comparison with others has the best result on soybean, especially on Caspian variety. In general, Caspian soybeans and thermal processing methods are recommended for replacing soybean meal in broiler chickens.

ACKNOWLEDGMENTS

We are grateful to the Islamic Azad University-Qaemshahr Branch, Iran for support.

REFERENCES

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  • Lichovnikova M, Zeman L, Kracmar S, Klecker D. The effect of the extrusion process on the digestibility of feed given to laying hens. Animal Feed Science and Technology 2004;116(3-4):313-318.
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  • Perilla NS, Cruz MP, De Belalcazar F, Diaz GD. Effect of temperature of wet extrusion on the nutritional value of full-fat soyabeans for broiler chickens. British Poultry Science 1997;38(4):412-416.
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  • Vandergrift WL, Knabe DA, Tanksley Jr TD, Anderson SA. Digestibility of nutrients in raw and heated soyflakes for pigs. Journal of Animal Science 1983;57(5):1215-1224.
  • Wondra KJ, Hancock JD, Behnke KC, Hines RH, Stark CR. Effects of particle size and pelleting on growth performance, nutrient digestibility, and stomach morphology in finishing pigs. Journal of Animal Science 1995;73(3):757-763.
  • Zarkadas LN, Wiseman J. Influence of processing of full fat soya beans included in diets for piglets:II. Digestibility and intestinal morphology. Animal Feed Science and Technology 2005;118(1-2):121-137.
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Publication Dates

  • Publication in this collection
    20 Dec 2019
  • Date of issue
    2019

History

  • Received
    06 July 2019
  • Accepted
    24 Sept 2019
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