Preparation Of Antioxidant Peptides Derived From Hairtail Protein

The imbalance of free radicals inside human body can cause irreversible oxidative damage, accelerate human aging and induce many diseases. External antioxidants can help people maintain the balance of free radicals inside body. Hairtail has high protein content and nutritional value, which makes it a very appropriate material for preparation of antioxidant peptides. For long time, due to the backwardness of processing and recycling means on hairtail, it results in low utilization and resource waste. Meanwhile it will cause environment pollution due to great loss of nutrients.Using hairtail protein as resource in this paper, the hydrolytic conditions were optimized and the antioxidant activities were assessed, then several methods were used to separate and purify the peptides. It provided a new way for preparation of antioxidant peptides and theoretical basis for deeply processing of hairtail protein.Controlled enzymatic technology, response surface methodology and orthogonal tests were used to optimize hydrolytic conditions, then the enzymatic hydrolysates with high antioxidant activity were obtained. The results showed that the optimum conditions for scavenging activity on DPPH free radicals was1:3(liquid-material ratio), enzyme addition1.65%, hydrolyzing for3.80h at48℃. For hydroxyl free radicals, it was1:2(liquid-material ratio), enzyme addition1.60%, hydrolyzing for5.50h at50℃.Scavenging activity under the above conditions were60.13%and58.73%respectively. For reducing ability, the optimum condition was1:6(liquid-material ratio), enzyme addition0.60%, hydrolyzing for5.00h at50℃.For ABTS+free radicals, it was1:20(liquid-material ratio), enzyme addition0.60%, hydrolyzing for120min at50℃.Reducing ability and scavenging activity on ABTS+free radicals under the above conditons were3.13and69.58%.For superoxide free radicals, the optimum condition was1:3(liquid-material ratio), enzyme addition3.20%, hydrolyzing for3.00h at50℃and the scavenging rate was47.31%.Hairtail protein was hydrolyzed by Alcalase2.4L, and a kinetic model for the hydrolysis was established. The result was as follows:at temperature50℃and pH8.0, the kinetic model formula was meanwhile inactivation constant for enzyme kd was57.410h-1. Compared with experiment result, the kinetic model fit well. It showed that the kinetic model had significant application value.Antioxidant peptides were isolated and purified by ultra filtration and consecutive chromatographic methods including ion-exchange chromatography, gel-filtration chromatography and reverse high-performance liquid chromatography. The purified antioxidant peptides on DPPH free radical scavenging rate was76.34%, which was27%higher compared with the crude hairtail peptides. It indicated that separation and purification methods could significantly improve antioxidant ability of hairtail peptides.