Chemical and biochemical evaluation of grains, soymilk and tofus of normal soybean and lipoxygenase-free soybeans

The objective was to evaluate the chemical composition and biochemical aspects of normal, normal bleached and lipoxygenase-free soybean cultivars and the processing effect of the respective soymilk and tofu. Chemical composition of normal and lipoxygenase-free soybean cultivars did not differ (p > 0.05). Changes in the chemical ascribed to the thermal treatment (98 degrees C/5 minutes) to which the normal soybean was submitted and to the grain soaking phase. In this phase it was evident that some hydrosoluble substances, leached to the grain maceration water, being that the bleaching of the normal soybean in the beginning of the processing reduced the content of some minerals in the soymilk and tofu. The soybean processing evidenced the losses of isoflavones in the tofu, in order of 38% in the normal soybean tofu, 31% in the bleached soybean tofu and 56% in lipoxygenase-free tofus. The thermal process used to obtain tofu was sufficient to eliminate the activity of the trypsin inhibitors by 79% in the normal soybean tofu, 81% in the bleached soybean tofu and 82% in lipoxygenase-free tofus.