DECREASE IN THE GEL STRENGTH OF TOFU CAUSED BY AN ENZYME REACTION DURING SOYBEAN GRINDING AND ITS CONTROL

The effect of soybean grinding temperature on the firmness of tofu was investigated. The firmness of tofu decreased with increasing grinding temperature between 0-degrees-C and 50-degrees-C, this being related to the content of sulfhydryl (SH) groups in soymilk. It could, therefo re, be presumed that the decrease in firmness depended upon the decrea se in SH content, which was of enzymatic nature and closely correlated with the peroxide value. These facts suggested that the decrease in S H content was caused by a lipid oxidative reaction of lipoxygenases in soybean. When the soybean was ground at a low temperature and in a ni trogen atmosphere to inhibit the action of lipoxygenase, the soymilk w as rich in SH content and formed firmer tofu.