Progress 10/01/01 to 09/30/04
Outputs
Glycinin-rich and beta-conglycinin-rich products are prepared by soy protein fractionation. Optimized conditions of 45C and 10:1 water-to-flake ratio were compared with previous conditions of 20C and 15:1 water-to-flake ratio and a soy protein isolate process at pilot scale using commercial defatted flakes. Optimized conditions yielded more beta-conglycinin with higher isoflavone and saponin concentrations, but fraction purity was diminished by glycinin contamination. Bench-scale data demonstrated that increased phytochemical extraction did not translate into increased concentrations in product fractions. Emulsifying properties were generally best for the 45C process intermediate and beta-conglycinin fractions. Beta-Conglycinin formed the firmest gels. These and other data suggest varied application suitabilities for these unique protein products. A 5 mM sodium sulfite improved yield & purity over control and the functional properties were improved for beta-conglycinin
but poorer for glycinin. A 2-step process replacing sodium chloride with calcium chloride maintained purities and improved beta-conglycinin yields in white flaks. Specialty soybeans (high sucrose/low stachyose; high oleic acid, Prolina or high cysteine) required additional processing modification for pilot plant purification of storage proteins. A phytase treatment during protein fractionation showed promise. Extraction temperature and pH affect protein solubilization from soy flakes and influence isoflavone and saponin partitioning and profile during isolate production. Soy slurry and process fractions resulting from extraction conditions of 25 or 60C and pH 8.5, 9.5, or 10.5 were investigated. High temperature and pH increased isoflavone and saponin extraction and substantially altered their profiles. Sample neutralization prior to extraction increased quantified isoflavone concentration of dried soy slurry, while neutralizing the isolate fraction dramatically increased quantified
saponin concentrations. Analytical extraction pH should receive careful consideration when analyzing a soy sample for isoflavones and saponins.
Impacts
Soy protein extraction procedures can be altered to improve soybean protein (glycinin and b-conglycinin) yields and alter their health protective phytochemical composition. Bitter taste thresholds for soy phytochemicals are lower in less processed soy products than in heated products. Therefore higher consumption of less processed soy protein products may yield greater health benefits without negative taste problems.
Publications
- Rickert, D.A., Johnson, L.A., Murphy, P.A. 2004. Improved Fractionation of Glycinin and β-Conglycinin and Partitioning of Phytochemicals. J. Agric. Food Chem. 52:1726-1734.
- Rickert, D.A., Johnson, L.A., Murphy, P.A. 2004. Functional Properties of Improved Glycinin and β-Conglycinin Fractions. J. Food Sci. 69:303-311.
- Rickert, D.A., Meyer, M.A., Hu, J., Murphy, P.A. 2004. Effect of Extraction pH and Temperature on Isoflavone and Saponin Partitioning and Profile during Soy Protein Isolate Production. J. Food Sci. 69:C623-C631.
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Progress 01/01/03 to 12/31/03
Outputs
Optimized conditions of 45 degrees C and 10:1 water-to-flake ratio were compared with previous conditions of 20 degrees C and 15:1 water-to-flake ratio and a soy protein isolate process at pilot scale. Optimized conditions yielded more beta-conglycinin with higher isoflavone and saponin concentrations, but fraction purity was diminished by glycinin contamination. Viscosity, solubility, gelling, foaming, and emulsification characteristics of the fractionated proteins and a soy protein isolate produced from the same defatted soy white flakes were compared. Emulsifying properties were generally best for the 45 degrees C process intermediate and beta-conglycinin fractions. beta-Conglycinin formed the firmest gels. These data suggest varied application suitabilities for these unique protein products. Two soybean varieties, Prolina A-1191 and A233HO, were compared with commercial soy flakes for differences in protein fractionation properties. Glycinin and b-conglycinin
contents were different among 3 types that affected protein fractionation in unexpected ways. Prolina and control were similar while A233HO, a high oleic variety, had reduced amounts of b-conglycinin. Wu process (Wu method, JAOCS 48:2702, 2000) did not work well with all varieties due to protein composition differences. Taste panels determined bitter flavor thresholds for isoflavones and saponins in water and in cow's milk. Bitter thresholds were highest in milk for extracts of soy protein isolate. DDMP-conjugated saponins and the malonyl-b-glucoside isoflavones have more off-flavor and/or are more bitter than other saponins and isoflavones found in soy. Furthermore, it would seem that less processed or heat treated soy products would have more off flavor or bitter flavor caused by isoflavones and saponins.
Impacts
Soy protein extraction procedures can be altered to improve soybean protein (glycinin and b-conglycinin) yields and alter their health protective phytochemical composition. Bitter taste thresholds for soy phytochemicals are lower in less processed soy products than in heated products. Therefore higher consumption of less processed soy protein products may yield greater health benefits without negative taste problems.
Publications
- Jung, S., Rickert, D.A., Deak, D., Aldin, E., Recknor, J., Johnson, L.A.., Murphy, P.A. 2003. Comparison of Kjeldahl and Dumas Nitrogen Methods for Protein Content Determination in Soy Products. J. Amer. Oil Chem. 80(12):1169-1173.
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Progress 01/01/02 to 12/31/02
Outputs
Laboratory-scale optimization of extraction pH and temperature, solvent/flake ratio and use of ethanol have been optimized for glycinin and b-conglcyinin fractionation and phytochemical retention. Pilot plant fractionations have been completed using solvent to flake ratio of 10/1, pH of 8.5 and extraction temperature of 45C. Ethanol use did not optimize to protein and phytochemical extraction rates. Increasing protein solubilization pH to 10.5 at 60C decreased the isoflavone/saponin in soy protein isolate by 2X. Neutralization prior to phytochemical analysis improves accuracy. Yields and mass balances and protein functionalities are being evaluated comparing optimized method with our previous published method and soy isolate production. Two soybean varieties (high methionine and high oleic) were evaluated for their protein fractionation rates using our standard extraction protocol (Wu method, JAOCS 48:2702, 2000). Yields ranged from 110-200% glycinin and 20-120%
b-conglcyinin depending on initial individual protein concentrations. Evaluation of solubilization of very denatured soy proteins and optimization of ionic strength and reducing strength in protein extract are in process. Taste panels have been completed to determine bitter flavor thresholds for isoflavones and saponins in water and in cow's milk. Thresholds were highest in milk for extracts of soy protein isolate.
Impacts
Soy protein extraction protocols can be altered to improve glycinin and b-conglycinin protein yields and alter phytochemical distribution in the products. These results suggest specific protein products and associated phytochemicals can be derived by appropriate selection of extraction and processing conditions. Taste thresholds established for bitter flavor of phytochemicals will set upper limit of phytochemicals in design of soy protein products to enhance health.
Publications
- No publications reported this period
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