Effect of cold and hot enzyme deactivation on the structural and functional properties of rice dreg protein hydrolysates

This study explored the effect of three different enzyme deactivation treatments: 4 °C slow cold deactivation (RDPH-(4 °C)), −18 °C rapid cold deactivation (RDPH-(−18 °C)) and 100 °C water bath (RDPH-(100 °C)), compared to that without enzyme deactivation (RDPH-(control)) on the structural and functional properties of rice dreg protein hydrolysates (RDPHs). The RDPHs from the different enzyme deactivation methods led to significant differences in the degree of hydrolysis, surface hydrophobicity, average particle size, intrinsic fluorescence and emulsion stability. FTIR analysis revealed that the strength of RDPH-(100 °C) spectrum peaks decreased significantly. All samples showed high solubility (>85%) and potent antioxidant capacity: DPPH (~90%), ABTS (~99%), and reducing power (0.86–1.03). Among the hydrolysates evaluated, the RDPH-(100 °C) led to the lowest reducing power and hydroxyl radical scavenging activity. Results reported here will be instrumental for the development of rice protein-based products and in the optimization and scale up of manufacturing process.