Assessment of gelatin hydrolysates from threadfin bream (Nemipterus hexodon) skin as a cryoprotectant for denaturation prevention of threadfin bream natural actomyosin subjected to different freeze-thaw cycles

Gelatin hydrolysates prepared from threadfin bream skin (GH) using lizardfish stomach pepsin (GHLP) with different degrees of hydrolysis (DHs: 10-40%) were studied as a potential alternative to commercial cryopro-tectant (sucrose/sorbitol blend; SuSo, 1:1) used in frozen surimi. The characteristics of threadfin bream natural actomyosin (NAM) containing 8% GHLP with different DHs or SuSo were compared to control NAM before and after freeze-thaw treatment. After 3 and 6 freeze-thaw cycles, all present cryoprotectants retarded the protein changes. Among all samples, the highest Ca2+-ATPase activity, total sulfhydryl and solubility with the coinci-dental lowest disulfide bond content were observed in NAM added with GHLP having 20% DH after repeated freeze-thawing. Also, GHLP could prevent lipid oxidation in NAM as shown by the lower TBARS value. When cryoprotective properties of GHLP with 20% DH and GH prepared by papain (GHP) (DHs: 10-40%) were compared, the cryoprotectant properties of GHLP were similar to that of GHP. However, GHP with 10% DH exhibited a higher protective effect on protein denaturation. Hence, both GHLP and GHP with suitable DH can be a new generation cryoprotectant with the lower sweetness in surimi products.

Automated summary

This study investigated the potential of gelatin hydrolysates prepared from threadfin bream skin using lizardfish stomach pepsin as an alternative cryoprotectant in frozen surimi. The results showed that the addition of gelatin hydrolysates with 20% degree of hydrolysis effectively retarded protein changes and prevented lipid oxidation. The cryoprotective properties of gelatin hydrolysates prepared with lizardfish stomach pepsin were similar to those prepared with papain.