Soybeans are subject to storage and shipping after harvest. During this period of time, the physical and biochemical characteristics of soybeans change to various degrees, depending upon the initial soybean moisture and storage/ shipping conditions, including various humidities and temperatures. Inappropriate storage will lead to product quality defects as well as major economic losses. The changes in soybean characteristics may include darkening in surface color, increase in hydration time, reduction in solid and protein solubility, decrease in phytate content, isoflavone structural conversions, changes in protein structures, sugar pattern and lipid oxidation. The coagulant requirement per unit weight of soymilk for tofu making is reduced by improper storage. The yield and quality of soymilk and tofu are also negatively affected by severe storage conditions. Significant correlations were found among quality attributes, including color parameters (Hunter L, a, b, and AE), solid extractability (as expressed by soymilk solids content), soymilk pH and protein content, tofu yield, hardness and protein content. We have developed simple statistical equations and kinetic models, which can be used to monitor soybean quality and predict quality changes of soybeans during storage.
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