响应面法优化超声辅助酶解制备藏系羊胎盘肽工艺及抗氧化能力分析

以藏系羊胎盘为原料，选取水解度、肽得率和抗氧化能力为指标，在蛋白酶种类筛选、双酶组合方案确定的基础上，通过单因素试验和响应面试验优化超声波辅助复合酶解制备羊胎盘肽的工艺条件，并分析其氨基酸组成和分子质量分布。结果表明，木瓜蛋白酶和中性蛋白酶同步复合酶解效果优于其他蛋白酶组合，水解度和肽得率分别为37.24%和13.54%。响应面优化结果显示各因素对水解度影响的主次顺序为：超声时间＞超声温度＞酶解时间＞超声功率；优化后的最优工艺参数为超声时间16.5 min、超声温度25.5 ℃、超声功率438 W、酶解时间4.9 h，该最优条件下的水解度为55.22%，肽得率为18.52%，抗氧化能力（Trolox当量）为1.08 mmol/L。藏系羊胎盘肽中富含谷氨酸、甘氨酸和天冬氨酸等，分子质量低于2 000 Da的肽比例为95.02%，绝大多数为小分子低聚寡肽。可见，超声波辅助酶解制备羊胎盘肽的工艺不仅能有效改善酶解效果，还能制得具有良好抗氧化能力的小分子肽。

Peptides from Tibetan Sheep Placental Protein: Optimization of Ultrasound-Assisted Enzymatic Preparation Using Response Surface Methodology and Antioxidant Activity Evaluation

In this paper, we optimized the conditions for ultrasound-assisted enzymatic preparation of peptides from Tibetan sheep placental protein (TSPP) using a combination of one-factor-at-a-time method and response surface methodology (RSM). Degree of hydrolysis (DH), peptide yield (PY) and antioxidant capacity were considered as the response variables. Six proteases and their binary combinations were screened for their suitability for the hydrolysis of TSPP preceding the optimization. Furthermore, the amino acid composition and molecular mass distribution of the hydrolysate prepared under the optimized conditions were determined. The results indicated that the simultaneous addition of papain and neutral protease was found to be the best hydrolysis scheme. The effects of sonication time, temperature, hydrolysis time and ultrasonic power on DH decreased in that order. The optimal hydrolysis parameters were obtained as follows: sonication time 16.5 min, temperature 25.5 ℃, ultrasonic power 438 W, and hydrolysis time 4.9 h, resulting in DH, PY and antioxidant capacity of 55.22%, 18.52% and 1.08 mmol/L Trolox equivalent, respectively. The resulting hydrolysate was rich in glutamic acid, aspartic acid and glycine and peptides below 2 000 Da accounted for 95.02% of the total peptides, the majority of which were small oligopeptides. In conclusion, the ultrasound-assisted enzymatic hydrolysis process could not only had improved hydrolysis efficiency but also produce small peptides with excellent antioxidant activity.