Production and functional characteristics of protein concentrates

Abstract

Protein concentrates derived from common dry beans (Phaseolus vulgaris L.) may improve world protein resources, reduce on-site preparation time and expense and provide improved nutrition. Several different methods have been studied for the production of these concentrates, including alkali extraction and isoelectric precipitation, ultrafiltration, air-classification and salt extraction under high salt concentrations. Recent studies using solid-solid dry roasting, pin milling and air-classification resulted in the following percent mass fractions: hull/fiber (10%), coarse/starch (70%) and fine/protein (20%). Results indicated that the protein fractions were approximately 45–50% protein, low in raffinose and stachyose and hadtrypsin inhibitor activity reduced to about half of that of raw beans. Nitrogen Solubility Index (NSI) ranged from 33–70% and was associated with the thermal conditions applied during dry roasting. The flours had a bland flavor without the bitter off-flavors which have traditionally limited the use of dry beans in formulated foods. Most minerals and phytic acid tended to be associated with protein flour; however, although iron may have been bound to phytic acid, its absorption by anemic rats was not hindered by the presence of endogenous phytic acid. These flours produced acceptable products when incorporated into cookies, doughnust, quick breads and leavened doughs.