Functional Properties of Soy Protein Isolate from Heat Treated Soybean

Effects of heat treatment on functional properties of soy protein were examined. Soy protein isolate (SPI) was prepared from Korean soybean varieties, Manli and Taekwang, subjected to heat treatment at for 30, 60, 90, and 120 min. pH-solubility results of SPI showed typical U-shape profiles with minimum solubility at pH 4-5 of isoelectric points of soy proteins, longer heat treatments showing slightly higher solubility. Water absorption, emulsifying activity, emulsion stability, and emulsion capacity of SPI increased, while oil absorption decreased, with heating time in Manli variety. Manli and Taekwang showed the highest emulsion capacities after 90-and 60-min heat treatments, respectively. Foam expansion of all SPIs increased with heating time up to 90 min. Texture profile analysis showed heat treatment up to 90 min significantly increased hardness, adhesiveness, springiness, gumminess, and chewiness, whereas significantly decreased cohesiveness of SPI gels (p