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

The cryoprotective activity of gelatin hydrolyzed by papaya latex enzymes at degrees of hydrolysis (DH) of 5%, 10%, 15%, and 20% were determined. The thermal hysteresis of gelati hydrolysate increased as DH increased up to 15% (2.31 - 4.19 degrees C) and decreased at DH of 20% (2.94 degrees C). The gelatin hydrolysate with 15%DH (G15), showing the highest thermal hysteresis, was subjected to fractionation and cryoprotective effect study in Pacific white shrimp. The fractionated peptide with the highest thermal hysteresis (5.19 degrees C) had a molecular weight of 1.7 - 4.2 kDa. After the soaking, G15 -treated shrimp showed significantly lower and higher weight gain (7.33%) than those treated with mixed phosphates (16.12%) and distilled water (0.82%), respectively. Mixed phosphatesand G15 -treated shrimp had lower alpha-glucosidase (AG) and beta -N-acetyl-glucosaminidase (NAG) activities in exudate and lower thawing loss than distilled water -treated shrimp. G15 -and mixed phosphates -treated shrimp also reduced freezable water content and maintained Ca 2+ -ATPase activity and protein solubility more effectively than distilled water -treated shrimp. Therefore, gelatin hydrolysate could be a potential alternative cryoprotectant in frozen raw shrimp.