Cryoprotective effect of gelatin hydrolysate from blacktip shark skin on surimi subjected to different freeze-thaw cycles

Abstract

The cryoprotective effects of gelatin hydrolysate from blacktip shark (Carcharhinus limbatus) skin with different degrees of hydrolysis (DHs:5, 10, 20 and 30%) and commercial cryoprotectant (sucrose/sorbitol blend, 3:1) on surimi from threadfin bream (Nemipterus spp.) subjected to 3 and 6 freeze-thaw cycles were investigated. Ca2+-ATPase, total sulfhydryl group content and solubility of all natural actomyosin (NAM) extracted from surimi decreased with increasing freeze-thaw cycles, while surface hydrophobicity and disulfide bond content increased (P < 0.05). Among all samples, the highest Ca2+-ATPase activity with the coincidental lowest surface hydrophobicity was observed in surimi added with gelatin hydrolysate having 10%DH after repeated freeze-thawing (P < 0.05). On the other hand, surimi without cryoprotectant showed the lowest Ca2+-ATPase and the highest surface hydrophobicity (P < 0.05). The similar solubility was obtained between samples added with commercial cryoprotectant and gelatin hydrolysate (10%DH) (P > 0.05). The results suggest that gelatin hydrolysate with 10%DH was able to prevent the denaturation of surimi protein comparably to commercial cryoprotectant. However, it exhibited the higher protective effect on denaturation of myosin heavy chain, especially globular head domain. Therefore, gelatin hydrolysate can be an alternative cryoprotectant with the lower sweetness in surimi products.