Effects of Heating Temperature and Cooling Rate on Denaturation of Soymilk Protein

In order to evaluate the effects of heating and cooling on soymilk protein, raw soymilk, which was squeezed before heating, was heated to 80, 100 or 115 degrees C and then cooled at room temperature or -5 degrees C. The surface SH content of the soymilk proteins decreased with increasing heating temperatures. Furthermore, the SH content of the soymilk that was cooled rapidly at -5 degrees C was higher than that of the soymilk that was cooled slowly at room temperature. The surface hydrophobicity of the soymilk proteins was increased by heating, and the hydrophobicity was slightly higher as a result of cooling at -5 degrees C compared with cooling at room temperature. The raw soymilk was first heated at 115 degrees C (first heating) and then 80 degrees C (second heating). After cooling in an ice bath, decreases in both the SH content and the hydrophobicity of the resulting soymilk were observed as a result of the second heating. This denaturation behavior is different from that of a protein solution prepared from defatted soybeans.