Solubility, emulsion stability and gelation of isolated soy proteins and their 7S and 1 IS fractions from three stages of seed maturity were studied. The pH-solubility profile was similar irrespective of maturation and sixmonth storage. The 1 IS protein was more soluble in the acidic pH range than the 7S protein. Oil-in-water emulsion stability of isolated soy protein from mature soybeans was higher than that from the immature ones. This is due to the fact that there was more 7S fraction in the mature soybeans, and 7S protein was found to form a more stable emulsion than that formed from 1 IS protein. The result suggests that isolated soy protein from mature soybeans would serve as a better emulsifying agent. Heat-induced soy protein gels became weaker as the soybeans became more mature. This can be attributed to the higher content in the immature soybeans of 11S fraction which gives a stronger gel than 7S fraction in the protein from immature soybeans.KEY WORDS: Disulfide content, effect of pH and storage, effect of salt, emulsion stability, gel strength, heat-induced gel, isolated soy proteins, NSI, 7S/11S ratio, soybean maturation.

Hack and Williams 82 soybeans from four maturation stages wcrc studied for storage stability and process quality. As compared to mature beans, trypsin inhibitor, ureasc and lipoxygenasc (LA) activities were lower in immature seeds, but free fatty acid (FFA) was higher and oil was greener. During storage for six months, LA dccrcased and FFA increased at a faster rate in immature than in mature soybeans. Crude oil and protein contents were similar, regardless of maturation or storage time. Both 7S and 11s proteins incrcascd with maturation but the 7S/llS ratio decreased. There was no change in protein during storage.

Bound wafer associated with freeze-dried 7S and 11s proteins was characterized by applying both sorption isotherm and proton pulsed NMR techniques. Over the a, range 0.10 to 0.97, the water binding capacity of the 7s protein was superior to that of the 11s protein.There was no significant difference in sorption capacity between unheated and heated proteins. The isotherms showed a biphasic linear relation so that two states of bound water, namely polymer and capillary water, were distinguished. NMR data followed isotherm data. The NMR mobility of the polymer water was less than that of the capillary water, as expected. However, high mobility was not related to high moisture content in the capillary water region.