茶渣多肽制备及其对羟自由基的清除能力

Preparation and Hydroxyl Free Radical Scavenging Activity of Tea Residue Polypeptides

分别以酸性蛋白酶、中性蛋白酶、碱性蛋白酶以及复合蛋白酶水解茶渣粗蛋白制备茶渣多肽,并对多肽的羟自由基清除能力进行考察。通过单因素试验证明:复合蛋白酶的效果最好,其最佳水解工艺条件为粗蛋白液质量分数0.5%、加酶量600U/g、温度55℃、pH8.0、水解5h,在此条件下,多肽对羟自由基的清除能力达27.3%;碱性蛋白酶的效果也较好,其最佳工艺为蛋白液质量分数0.5%、加酶量400DU/g、pH8.5、温度50℃、时间1.0h,在此条件下,多肽对羟自由基的清除能力达25.3%,与前者的清除能力没有显著差异,但用时少4h;利用碱性蛋白酶作为酶源制得茶渣多肽粗品中含有蛋白质、多肽、游离氨基酸分别为28.4%、11.0%、1.5%,其对羟自由基的半清除率IC50为8.432mg/mL,相同条件下VC的IC50为0.897mg/mL。

In order to establish an enzymatic method to hydrolyze crude tea residue protein to prepare tea residue polypeptides with higher hydroxyl free radical scavenging activity, the effects of enzymes （acidic protease, neutral protease, alkaline protease and protamex）, substrate concentration, enzyme dosage, temperature, pH, hydrolysis time on hydroxyl free radical scavenging activity were studied. Protamex was the best enzyme for the preparation of tea residue polypeptides with hydroxyl free radical scavenging activity, followed by alkaline pmtease and the optimal substrate concentration, enzyme dosage, hydrolysis temperature, pH and hydrolysis time were 0.5%, 600 U/g, 55 ℃, 8.0 and 5 h for protamex hydrolysis, and 0.5%, 400 DU/g, 8.5, 50 ℃ and 1.0 h for alkaline protease hydrolysis, resulting in a hydroxyl free radical scavenging rate of 27.3% and 25.3%, respectively. Compared with protamex hydrolysis, alkaline protease hydrolysis resulted in a decrease in time consumption by 4 h despite showing no significant difference in hydroxyl free radical scavenging capacity. The polypeptide sample obtained by alkaline protease hydrolysis contained 28.4% protein, 11.0% polypeptide and 1.5% free amino acids and indicated an IC50 of 8.432 mg/mL against hydroxyl free radicals compared with 0.897 mg/mL for vitamin C .