Effect of heat treatment on the release of off-flavor compounds in soy protein isolate.

The effects of different heat treatment conditions (65℃ for 30 min, 75℃ for 15 min, and 95℃ for 2, 15 and 30 min) on the evolution of off-flavor compounds in soy protein isolate (SPI) were investigated in terms of lipid oxidation, Maillard reaction and protein structural characteristics. Higher off-flavor concentrations were observed in control and 65℃ treated SPI due to lipoxygenase-mediated enzymatic lipid oxidation. Protein structure played an important role in the release of off-flavors above 65℃. When heated from 75℃ to 95℃ for 2 min, Maillard reaction occurred, glycinin was completely denatured, the particle size increased and the small molecular weight soluble aggregates were formed, resulting in an increase in the content of partial off-flavors. The off-flavor content decreased with time at 95℃, accompanied by the formation of larger molecular weight soluble aggregates. This finding provides practical implications for the beany removal through the SPI structural regulation.