Electron beam irradiation induced aggregation behaviour, structural and functional properties changes of rice proteins and hydrolysates

This study observed that the solubility of rice protein was improved by electron beam irradiation-assisted enzymolysis with a 1.9-fold and 10-fold increase relative to nonirradiated hydrolysate and protein, followed by the enhanced emulsifying properties. The emulsifying activity and stability of hydrolysates at irradiation dose of 75 kGy increased by 145% and 204% of that of nonirradiated samples, respectively. Additionally, the storage and loss modulus of protein and hydrolysates during thermal gelation process were increased by electron beam irradiation. Meanwhile, the mechanisms of aggregation and structural changes of rice proteins and hydrolysates under irradiation were illustrated by subunit composition, secondary structure, tertiary structure and morphological characterization. Atomic force microscopy showed that greater protein aggregation and cross-linking of peptides appeared after irradiation. The increased beta-sheet and decreased surface hydrophobicity proved that hydrophobic aggregates of irradiated proteins formed through hydrogen bonding and hydrophobic interactions. Conversely, soluble aggregates of hydrolysates involved the exposure of hydrophobic and sulfhydryl groups and formation of some noncovalent interactions via exposed reactive resides. This study clarified the relationship between aggregation behavior, structural changes and functional properties, which will provide a feasible method to improve the quality of rice protein in food industry.