Study on Preparation of Whole Grain Polypeptides by Semi-solid Enzymatic Hydrolysis and Their Antioxidant and ACE Inhibitory Activities

Cereal polypeptides were prepared by semi-solid enzymatic hydrolysis with oat and buckwheat as substrates and their antioxidant and hypotensive abilities were studied, liquid enzymatic hydrolysis was used as the control group. Kjeldahl method was used to determine the content of peptides in the enzymatic hydrolysate, reducing antioxidant power (FRAP), hydroxyl radical scavenging capacity, and Angiotensin I converting enzyme (ACE) activity inhibition experiments were used to determine the antioxidant and blood-pressure lowering properties of enzymatic products. The results showed that the hydroxyl radical scavenging rates of 1 mg/mL oat and buckwheat polypeptide (semi-solid enzymolysis group) were 61.34% and 69.33%, the total antioxidant capacity was equivalent to (0.53±0.03) mmol/L and (0.48±0.01) mmol/L FeSO₄, and the inhibition rates of ACE were 80.27% and 77.60%, respectively. Based on the peptide content, antioxidant and ACE inhibitory activity of the enzymatic hydrolysis products, the optimum technological parameters of semi-solid enzymatic hydrolysis was as follows: oats with the enzymatic hydrolysis time 3 h, enzyme added 3.75%, and buckwheat with enzymatic hydrolysis time 1 h, enzyme added 2.50%.At the optimum enzymatic hydrolysis parameter, the content of polypeptides in the enzymatic hydrolysis products of oat and buckwheat was 7.03% and 6.35%, respectively. The yield of polypeptide and antioxidant and ACE inhibition ability of semi-solid enzymatic hydrolysis group were significantly higher than those in liquid enzymatic hydrolysis group. The semi-solid enzymatic hydrolysis process can not only improve the efficiency of hydrolysis, but also improve the antioxidant and ACE inhibitory activity of cereal peptide. It also can provides theoretical support for high-value processing of grain and application of functional food ingredients.