Study On The Preparation Of Shrimp Peptide(Metapenaeus Affinis) And Its Antioxidant And Anti-fatigue Activities

Antioxidant peptides of Metapenaeus affinis were prepared through controlled enzymatic technology. The antioxidant activities in vitro and in vivo of shrimp hydrolysates(SH) were evaluated, as well as their anti-fatigue activities in vivo. And then several isolation and separation technologies were used to purify the SH and ESI-MS/MS was used to identify the amino acid sequence of SH. Besides, the impacts of the processing and storage ways to the antioxidant activities of SH were also evaluated in this study.The assays of protein recovery, degree of hydrolysis, reducing power and scavenging activities of DPPH radical were used to evaluate the eight hydrolysates of four shrimps which were hydrolysis by two enzymes. The hydrolysates of Metapenaeus affinis using papain were chosen and a resonance surface analysis was chosen to optimize the hydrolysates. The enzymatic hydrolysis process was optimized based on DPPH radical scavenging activities and oxidative free radical absorbance capacity(ORAC). The optimal enzymatic hydrolysis conditions were enzyme dosage 1000 U/g, enzymatic hydrolysis time 2.7h and liquid-to-solid ratio 1:0.5. The actual DPPH radical scavenging activity and the ORAC value of SH was 81.6 ± 0.4 % and 750.75 ± 40.7 μmol trolox/g, respectively, without significant difference compared with the predicted value(p>0.05).The antioxidant activities of shrimp hydrolysates(SH) were assessed. The results indicated that SH could scavenge DPPH radical(IC50 value was 2.87 ± 0.03 mg/m L) and ABTS radical(IC50 value was 1.10 ± 0.02 mg/m L), enhance the reducing power(0.316 ± 0.004 at 4 mg/m L) promote the oxygen radical absorbance capacity(ORAC) value(750.75 ± 40.72 μmol Trolox /g). Besides, the anti-fatigue activity and antioxidant activity experiments in vivo showed that SH significantly prolonged the swimming time, increased the liver glycogen, reduced the blood urea nitrogen(BUN) levels and improved the activities of GSH-Px and CAT compared to the control group(p<0.05).SH was isolated and purified by HP-20 macroporous resins chromatography, Sephadex G-25 gel filtration chromatography and RP-HPLC. Through the analysis of ESI-MS/MS, the peptides was identified as Gly-Phe-Trp(408.18 Da) with great ORAC value, which was 11.1 times of that of GSH.The impacts of temperature, p H value, food ingredients, metal ions, drying techniques and storage ways to the antioxidant activities of SH were evaluated. The results showed that the effect of temperature to SH had no significant difference. The antioxidant activity of SH was slightly raised in the acidic condition, while it declined in alkaline condition. With the increase of glucose, the antioxidant activity of SH was descended. while the dose of sucrose and Na Cl was no significant effect on that of SH. Cu2+ and Zn2+ ions were significantly decrased the antioxidant activity, while Mg2+, Ca2+, K+ ions had no effect to the antioxidant activity. Spray drying and freeze drying also had no significant effect to the antioxidant activity. After 20 d freezing storage, the antioxidant activity of SH was stable. However, the antioxidant activity of SH was decrased quickly after 10 d cold storage.