Abstract: Objective: The purpose of this study was to explore the impact of dry heating time on the Maillard reaction between rice bran polysaccharide (RBP) and whey protein isolate (WPI) in order to develop a new emulsifier for the preparation of nanoemulsions encapsulating lipid-soluble substances. Methods: The changes in absorbance at 294 nm (A294 nm), browning degree, color and free amino acid content were monitored during the Maillard reaction under dry heating condition, and the molecular mass, particle size, emulsifying activity and emulsion stability, and microstructure of the reaction product were characterized. Meanwhile, the Maillard reaction product was used to prepare soybean oil nanoemulsion. Results: As indicated by the changes in A294 nm, browning degree, color difference and free amino acid content, the Maillard reaction took place, and the color of the product became darker with an increase in reaction time. The molecular mass of the reaction product was 17 kDa, and a uniform particle size distribution was observed at 12 h of reaction. The Maillard reaction significantly improved the emulsifying activity and emulsion stability of WPI (P < 0.05). Nanoemulsion containing WPI-RBP complex at 12 h of reaction was more stable than the one containing WPI and showed uniform particle size distribution, and it could resist the negative impact of acid and salt ions. Conclusion: The Maillard reaction between WPI and RBP effectively improve the emulsifying properties of WPI, and the reaction product can be used as a new emulsifier in the food field.

Key words: rice bran polysaccharide; whey protein isolate; Maillard reaction; characterization; stability