Effects of rice bran milling fractions on the eating quality, starch digestion properties, and flavor characteristics of steamed bread.

Three rice bran fractions (BF1, BF2, and BF3) were obtained through sequential milling. Increasing the degree of milling was found to significantly reduce the content of total dietary fiber, total phenolics, and total flavonoids in rice bran. Steamed bread (SB) was prepared by replacing wheat flour with rice bran at substitution levels of 5%, 10%, and 15%. Notably, substitution levels above 10% increased the hardness of SB, and imparted a distinct bran off-flavor. In contrast, 5% substitution enhanced the antioxidant activity and reduced the starch hydrolysis rate. Among all samples, the BF1-5% group exhibited the most pronounced effects, with the estimated glycemic index reducing from 97.53 to 81.97. Furthermore, the BF1-5% and BF2-5% groups showed significantly higher concentrations of characteristic volatile compounds (e.g., 3-methyl-1-butanol, 2-methylpropanoic acid, ethyl acetate). These findings indicated that substituting wheat flour with BF1-5% can significantly enhance the nutritional value, functional properties, and sensory quality of SB.