Antioxidant and cryoprotective effects of a tetrapeptide isolated from Amur sturgeon skin gelatin

The peptide Pro-Ala-Gly-Tyr (PAGT) was isolated from Amur sturgeon skin gelatin and its antioxidant activity and cryoprotective effect in Japanese sea bass (Lateolabrax japonicus) mince was investigated. PAGT showed scavenging activity against DPPH, ABTS and hydroxyl radicals with no metal chelating activity. At a level of 25 ppm, PAGT prevented lipid oxidation in minced fish, but at higher levels it was ineffective. Low-field nuclear magnetic resonance (LF 1H NMR) detected three water pools in mince in the range of 1-10, 10-100 and 100-300 microsecond (ms), respectively. PAGT influenced water distribution in the mince. Mince with PAGT (25 ppm) had the highest T21 population, corresponding to a lower amount of water in T22 population after 6 freeze/thaw cycles (P < 0.05). Myosin and actin denaturation decreased in the presence of PAGT. Lipid oxidation in mince was impeded when PAGT was incorporated at 25 ppm as evidenced by the lower hydroperoxides from Fourier transform infrared (FTIR) spectra.