Effect of the denaturation degree of defatted soy flakes on structural properties and storage stability of produced protein isolate

The objective of this study was to reveal the influence of different denatured material on the storage stability of soy protein isolate(SPI),as well as its relationship with the structural properties. SPI that prepared from soybeans was considered to be the control. Three SPI samples were extracted from defatted soy flakes(with denaturation degrees of 72.6%,29.4%,1.8%,separately) and stored(37℃) for 10 weeks. The storage stability was evaluated by tracking protein solubility during storage and the initial structural properties were then determined. Results showed that,the control exhibited the highest protein solubility(93%) at the initial state of storage,and the least decline after 10-wk storage. The highest denaturation degrees of the defatted flakes,the lowest initial solubility was found in the resulted SPI,SPI with higher initial solubility showed faster decline rate during storage,reduced to the same level after 10 weeks. Furthermore,SPI that extracted from high-denatured material displayed high aggregation or dissociation degree,which was harmful to the protein solubility of short-time(≤6wk) stored sample. When the samples shared similar denaturation degree and the initial solubility,SPI with higher level of aggregation or dissociation exhibited higher rate of solubility decline after long-time(>6wk) storage. In addition,disulfide linkage was the main covalent bond mediated in protein aggregation,and some other covalent bond was also found in high denatured sample.