Effects of moisture and temperature during grain storage on the functional properties and isoflavone profile of soy protein concentrate

- Protein concentrate was obtained from soybeans stored under different conditions.
- Storage of soybeans with 12% moisture at 11 °C preserves the functional properties.
- Storage of soybeans at 32 °C reduced the protein extraction yield.
- Storage of soybeans at 32 °C reduced the solubility of the protein concentrate.
- Storage of soybeans at 32 °C increased the proportion of isoflavones in aglycone form.

The objective of this study was evaluate the effects of moisture and temperature during grain storage on the functional properties and isoflavone profile of soy protein concentrate. The protein concentrate was extracted from soybeans on the first day of storage and after 12 months of storage, at 12 and 15% moisture and at temperatures of 11, 18, 25, and 32 °C. The protein concentrate obtained from grains stored at 32 °C showed decreased extraction yield (51.6% with 15% of moisture) and protein solubility (24.8% with 15% of moisture) with increased emulsifying capacity (52.2% with 12% of moisture) and foam formation, compared with sample obtained at the start of the storage period. The isoflavone profile showed a decrease in the concentrations of glycosylated, malonyl, and acetyl isoflavones and a corresponding increase in the concentrations of aglycone isoflavones, with the magnitude of these changes increasing with increasing storage temperature and moisture content.