Objective  The study investigated the effects of various proteases on the enzymatic hydrolysis of protein from Hongqu glutinous rice wine grains, followed by a functional evaluation of the resulting enzymatic hydrolysate. The purpose was to provide theoretical support for the development and preparation of protein peptides derived from Hongqu glutinous rice wine grains protein.

  Method  Purified Hongqu glutinous rice wine grains were utilized as the raw material, employing various proteases, including alcalase, trypsin, animal protease, papain, bromelain, pepsin, compound enzyme preparation F106, and yeast extract enzyme, for enzymatic hydrolysis. The enzymatic hydrolysis rate, 1,1-diphenyl-2-picrylhydrazyl (DPPH), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) free radical scavenging antioxidant ability, xanthine oxidase (XOD), and angiotensin-converting enzyme (ACE) inhibitory activity, along with other biological activity functions, were described.

  Results  The peak proteolytic rates for animal protease and trypsin were (71.43±1.03)% and (70.20±0.32)%, respectively. Among the hydrolysates, those derived from pepsin, alcalase and yeast extract enzyme exhibited the best DPPH free radical scavenging antioxidant capacity. The median effective concentration(EC₅₀) of peptides were (2.78±0.34) mg·mL⁻¹, (3.02±0.03) mg·mL⁻¹ and (3.24±0.65) mg·mL⁻¹, respectively. The hydrolysates of pepsin and alcalase exhibited superior ABTS scavenging and XOD inhibition capabilities. The protein of peptides EC₅₀ values were (1.54±0.07) mg·mL⁻¹, (6.45±0.27) mg·mL⁻¹, (10.71±0.06) mg·mL⁻¹, and (17.68±0.04) mg·mL⁻¹, respectively, while their half inhibitory indices of XOD were (1.28±0.01) and (1.78±0.03), respectively. Alcalase and papain hydrolysate showed themostoptimal ACE inhibitory activity. The EC₅₀ of the peptides were (0.27±0.01) mg·mL⁻¹ and their half inhibition indices were (118.40±2.53) and (98.35±1.95), respectively.

  Conclusion  The peptides derived from the protein of Hongqu glutinous rice wine grains exhibit different biological activities after enzymatic hydrolysis by various proteases. Among them, the XOD inhibitory activity of pepsin enzymatic hydrolysis is stronger, and the ACE inhibitory activity of alcalase and papain enzymatic hydrolysis is better.