Abstract: For a better understanding of the difference in functional components and functions among different parts of highland barley bran, the contents of protein, β-glucan and polyphenol, antioxidant activity, and alkyl radical intensity in highland barley bran with various milling rates were compared. The results showed that the contents of total protein, albumin, globulin, glutenin, free polyphenol, bound polyphenol, free flavone, bound flavone and condensed tannin first increased and then decreased with increasing milling rate. Protein mainly existed in bran flour with a milling rate of 17.74% and 19.22%. Bran flour with 9.7% milling rate had the highest phenol content, and the trend in antioxidant activity was consistent with that in the content of phenols. The contents of β-glucan and gliadin increased from outside to inside, and reached the highest value at a milling rate of 25.99%. Alkyl radical intensity was significantly higher at 1.54%–5.84% milling rates than at 7.67%–25.99% milling rates, indicating a higher susceptibility to oxidation. The findings of this study provide a theoretical basis for the deep processing of different layers of highland barley bran.

Key words: highland barley bran; layered grinding; functional components; antioxidant activity; alkyl radical