Gelatin hydrolyzed by papaya latex enzymes as an alternative cryoprotectant for frozen raw Pacific white shrimp (Penaeus vannamei)

Abstract The cryoprotective activity of gelatin hydrolyzed by papaya latex enzymes with the degree of hydrolysis (DH) of 5, 10, 15, and 20% was investigated. The cryoprotective activity of gelatin, as determined by thermal hysteresis, increased as DH increased up to 15% (9.14–16.60 °C) and decreased as DH of 20% (11.66 °C). The gelatin hydrolysate with DH of 15% (G15), which showed the highest thermal hysteresis, was subjected to fractionation and cryoprotective effect study in Pacific white shrimp. The fractionated peptide with the highest thermal hysteresis had a molecular weight of 1.7–4.2 kDa (18.81 °C). According to the study of the cryoprotective effect in Pacific white shrimp, the weight of shrimp gained 7.33% after soaking in the G15, which was significantly lower and higher than the weight gain of shrimp treated with mixed phosphates (16.12%) and distilled water (0.82%), respectively (P < 0.05). The shrimp treated with mixed phosphates and G15 had no exudate. The thawing loss of the shrimp treated with distilled water, mixed phosphates, and G15 after the different freeze-thaw cycles ranged from 7.43–9.25, 3.34–3.57, and 3.39–5.39%, respectively. The shrimp treated with G15 and mixed phosphate could retard shrimp quality loss from the freeze-thawing, as noticed by the lower reduction of exudate loss, thawing loss, freezable water content, Ca2+-ATPase activity, and the higher protein solubility than the treatment of water. Therefore, the gelatin hydrolysate could be a potential alternative cryoprotectant in frozen raw shrimp.