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Co-processing Soy Proteins and Milk Proteins with Commercial Ultrafiltration Membranes
This research was funded by the American Soybean Association, St. Louis, MO. Appreciation Is expressed to Carolyn J. Hines and Billie B. Hefti for technical assistance in obtaining analytical data and to the Grain Processing Corporation, Muscatine, IA for conducting PER tests.
ABSTRACT
Ultrafiltration (UF) membranes were used to co-process soy protein extract and skim milk seeking to produce soy-milk food ingredients with protein efficiency ratios (PERs) of 2.5 or higher. Extracts from two commercial soy flours and ground soybeans were blended with commercial skim milk before and after ultrafiltration. Protein blends of 67% soy-33% milk, 50% soy-50% milk and 33% soy-67% milk were processed. Soy-milk products possessed high nitrogen solubility and light color. Lysine contents of soy-milk products ranged from 7.34–6.82%. PERs ranged from 2.36 for 33% soy-67% milk to 1.47 for UF soy isolate without milk. Soy and milk proteins exhibited some synergistic effects, but none of the soy-milk PERs reached the 2.5 level.