Gelatin hydrolysate in freeze–thawed shrimp model system: cryoprotective and antioxidative effects

The gelatin hydrolysate from Nile tilapia skin (TGH) produced by the hydrolysis of papaya latex enzymes for 0.5 (TGH-0.5), 1 (TGH-1), 2 (TGH-2), 3 (TGH-3) and 6 h (TGH-6) was used for determination of the degree of hydrolysis (DH), molecular weight distribution, and cryoprotective and antioxidative activities. The DH of gelatin hydrolysate ranged from 11.16 to 19.44%. TGH-0.5, TGH-1, TGH-2, TGH-3 and TGH-6 had the dominant peptides with MW of 3127 Da; 2325 and 2830 Da; 1658 and 1754 Da; 1206 and 1361 Da; 898, 1206, and 1361 Da, respectively. TGH-3 and TGH-6 showed the highest cryoprotective effect (P < 0.05). TGH showed an increase in DPPH and ABTS radical scavenging activities, FRAP, and chelating activity as the hydrolysis time increased (P < 0.05). The selected gelatin hydrolysate (TGH-3) could maintain the enthalpy of actin and myosin in the freeze–thawed shrimp more than the control and comparable to the mixed phosphate. Treating TGH-3 and the mixed phosphate could slow the lipid oxidation rate at the fifth freeze–thaw cycle and showed inhibition efficiency equivalent to the mixed phosphate. Therefore, gelatin hydrolysate could be an alternative additive substitute for mixed phosphate to inhibit the shrimp quality loss from ice formation, ice recrystallisation and lipid oxidation during frozen storage.