92D-14 |
Production of soy protein concentrate by ultrafiltration and comparison of its functionality with conventional acid-precipitated protein products |
H. KIM1, B. K. Kim2, and K. C. Rhee1. (1) Food Protein R&D Ctr., Texas A&M Univ., Cater-Mattil Hall, 2476 TAMU, College Station, TX 77843-2476, (2) Dept. of Food Engineering, Dan Kook Univ., San-29, Anseo-Dong, Cheonan, 330-714, South Korea Recover proteins using ultrafiltration (UF) process is an attractive alternative to conventional acid-precipitation method. The mild processing condition which leads to less protein denaturation maybe one of major virtues of this method. This research is directed to identify such assumptions of the products. Full-fat soybean flour, previously dry-heated (170C, 2min) before grinding was dispersed into d-water (1:7) at 60C. A series of operations including pH adjustment (8.0), agitation (250rpm, 30min), sonication (40dB, 20min), homogenization (3min), and centrifugation (3,000xg, 15min) were followed. For the membrane processing, a benchtop system (QSM-02S, A/G Technology Co., MA) equipped with UF cartridge (NMWC 100,000) was used. Acid-precipitated proteins (at pH 4.5) were obtained following the identical procedures as above except the use of hexane-defatted soybean meal. Samples consisted of protein extracts from: full-fat flour and UF retentate (FM); defatted flour and UF retentate (DM); defatted flour and acid-precipitation (DA). Protein contents ranged from 63.5%(FM) to 71.9%(DA) and all the products were closer to commercial SPC in definition. Nitrogen solubility values ranked as FM (97.8%) > DM (93.2%) > DA (85.9%), according to protein denaturation. In appearance, DA was distinct in greenish tint from others with lower "a" values. Emulsion capacity was highest in DA (105.0mL) as compared to FM (91.1mL) and DM (97.5mL) while emulsion stability was in the opposite direction. Both foaming capacity and stability from DA were the highest. Heat coagulations were higher in FM and DM than DA. Amino acid patterns followed the typical one of soy proteins. However relatively low glycine, alanine, and arginine contents in DA were noteworthy. The SDS-PAGE electrophoretic patterns were almost comparable among samples. All samples were comparable in their functional properties. However, if toasting/desolventization which is a customary practice in industry is considered, a membrane-recovered protein is expected to provide better functions in emulsion protein-food products.
Session 92D, Quality Assurance: General
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