PREPARATION AND PROPERTIES OF PROTEIN ISOLATE FROM HEXANE ACETIC-ACIDTREATED COMMERCIAL SOYBEAN-MEAL

Protein isolates were prepared from commercial soy meal treated with h exane containing 3% acetic acid at 28 and 58 degrees C. The sensory, p hysicochemical, and functional characteristics of the spray-dried isol ates were determined. The yield of isolate on the protein basis for co ntrol meal was 66%, while that of isolate from treated meals decreased by 12-18.2%. The trypsin inhibitor activity (52 TIU/mg of protein) of isolates was reduced significantly compared to that of its correspond ing meal (138 TIU/mg of protein). Sensory evaluation studies showed a 66% reduction in beany flavor in treated isolates. In gel electrophore sis, the isolate from treated meal at 58 degrees C showed dissociation and aggregation, and fluorescence measurements indicated quenching du e to unfolding of the protein molecule. At pH 7.0, the nitrogen solubi lity of isolate from the meal treated at 58 degrees C was higher (95%) compared to that of other isolates (82-85%). Higher fat absorption va lues for both treated isolates but superior emulsifying properties onl y in isolate from meal treated at 58 degrees C were observed. However, there was no change in foaming capacity values. Use of higher tempera ture (58 degrees C) for extraction had a beneficial effect in terms of improved functionalities.