EFFECTS OF THERMAL-TREATMENT OF SOY PROTEIN ISOLATE ON THE CHARACTERISTICS AND STRUCTURE-FUNCTION RELATIONSHIP OF SOLUBLE AND INSOLUBLE FRACTIONS

Aqueous dispersions (5-15% w/w) of native soy protein isolate were thermally treated at 80 and 100 degrees C for 30 min. At 100 degrees C, both 7S and 11S proteins were totally denatured, while at 80 degrees C, the 7S protein was totally denatured but the 11S protein was not, the denaturation degree of which was only partial and dependent on the extent of isolate denaturation. The different behaviors were reflected in the degree of aggregation, which in turn determined the yields and structural characteristics (denaturation degree, molecular weight distribution, superficial hydrophobicity, Mg2+ induced aggregation) of soluble and insoluble fraction obtained from treated isolates. A study was then performed on the effects of such structural changes on some functional properties (solubility, water imbibing, gelling and foaming properties) of soluble and insoluble fractions and, consequently, those of the total isolate.