Pyrazine yield and functional properties of rice bran protein hydrolysate formed by the Maillard reaction at varying pH.

Abstract

Interest in plant-based protein sources has grown rapidly. Rice bran contains excellent quality protein, but it is still rare in the market, due to its poor functional properties and undesirable odors. Therefore, we studied the Maillard reaction at different pHs on the formation of pyrazines and improved functional properties of rice bran protein hydrolysate. Protein from rice bran was extracted and hydrolyzed, using alcalase, at 55°C for 4h. Fructose was added, and the pH of the hydrolysate was adjusted to pHs between 7.0 and 10.0, before spray drying. Five pyrazines were detected in the hydrolysate powder, with the highest yield at pH 9 ( p < 0.05). The highest odor active value came from 2-ethyl-3,5-dimethylpyrazine (26.26), which contributed coffee,nutty and caramel aromas, followed by 2,5-dimethylpyrazine (9.2) and 2-ethyl-5-methylpyrazine (5.0). Increased pH led to a darker color (L* = 58.5) and redder (a* = 11.7) and yellower (b* = 13.8) powder. Key functional properties-solubility, water and oil binding capacity and emulsion stability index and foaming capacity-were increased with pH ( p < 0.05). The optimum pH for pyrazine formation and improved properties of enzymatic rice bran protein hydrolysate was pH 9.0.