Abstract: To address the problem of quality deterioration in soybeans imported from Brazil to China during storage and transportation, this study systematically explored the effects of different storage temperatures (25, 30, 35, and 40 ℃) on their biochemical characteristics and storage quality. Electrical conductivity, malondialdehyde (MDA) content, crude fat quality, and catalase (CAT), peroxidase (POD) and polyphenol oxidase (PPO) activities were measured. Electrical conductivity and crude fatty acid value were selected as indicators sensitive to storage conditions based on coefficients of variation. Kinetic models for predicting quality changes in Brazilian soybeans during storage were established based on the sensitive indicators. The results showed that with increasing storage temperature or storage period, electrical conductivity, MDA content, crude fat acidity, and peroxide value (PA) increased significantly, while crude fat content and enzyme activities such as CAT decreased significantly. Correlation and coefficient of variation analyses indicated that both electrical conductivity and crude fat acid value were significantly correlated with storage time and temperature and showed significant changes during storage. The changes in electrical conductivity and crude fat acid value conformed to zero-order kinetic models, and the kinetic constants increased with increasing storage temperature, indicating decreased stability of Brazilian soybeans. The activation energies for electrical conductivity and crude fat acid value were 49.24 and 67.14 kJ/mol, respectively, suggesting that electrical conductivity changes more readily than crude fat acid value during storage. A kinetic model was developed to describe electrical conductivity as a function of storage temperature and time. This model enables the prediction of the safe storage period of soybeans based on storage conditions or the estimation of the storage temperature required to achieve a specific storage period, providing a theoretical basis for predicting quality changes in Brazilian soybeans during storage and for formulating scientific storage protocols.

Key words: Brazilian soybeans; storage; temperature; quality changes; kinetic analysis