The Influence Of Silver Carp Skin Gelatin Hydrolysate On The Quality Of Unwashed Fish Mince

Freshwater fish mince is prone to chemical deterioration during frozen storage,especially lipid oxidation and protein denaturation with a significant source of lipids and proteins.Due to possible toxicity and carcinogenic effects of synthetic antioxidants and sweetness of commercial cryoprotectant,the natural additives have gained increasing attention.Protein hydrolysate,mostly derived from by-products during aquatic products processing,have been demonstrated to exhibit antioxidative and cryoprotective effects in fish mince.The article aimed to investigate the influence of enzyme type and degree of hydrolysis on the antioxidant and cryoprotective effects of gelatin hydrolysate in unwashed fish mince.The results are as follows:(1)The basic component of pretreatment fish skin and the extraction of gelatin.After dealing with Na OH and ethyl acetate,pretreated fish skin contains moisture 74.2%,protein 25.4%,lipid 0.58%and ash 0.38%(wet base),and gelatin was extracted from silver carp skin with the yield 84.6%.(2)Gelatin was separately hydrolyzed by different proteases,including alcalase,papain and flavourzyme,and the influence of enzyme type on the antioxidant and cryoprotective effects of gelatin hydrolysate was evaluated.The gelatin hydrolysate prepared using flavourzyme had the greatest scavenging activity against DPPH·and reducing power,whereas the gelatin hydrolysate of alcalase showed the highest ferrous ion chelating activity.The addition of gelatin hydrolysate prepared using flavourzyme into unwashed mince lowered the TBARS and dityrosine,retarded the salt soluble protein decreasing,prevented Ca²⁺-ATPase losing and improved the ability of unwashed fish mince maintaining water as compared to the control during freeze-thaw cycles.(3)Influence of degree of hydrolysis on the antioxidant and cryoprotective effects of hydrolysate with flavourzyme,and the antioxidant and cryoprotective effects of different gelatin hydrolysate in unwashed fish mince were investigated.The gelatin hydrolysate with 32.6%DH had the greatest scavenging activity against DPPH·and ferrous ion chelating activity,and gelatin hydrolysate with 20.8%DH show the highest reducing power.The addition of gelatin hydrolysate with 20.8%DH into unwashed fish mince was the most effective to retard the salt soluble protein decreasing,prevent Ca²⁺-ATPase losing and improve the ability of fish mince maintaining water as compared to the control during freeze-thaw cycles.The hydrolysates with 20.8%DH and 32.6%DH had no significant difference in lowering TBARS and dityrosine.In summary,the the gelatin hydrolysate of flavourzyme with 20.8%DH and 32.6%DH are effective in preventing lipid oxidation and protein denaturation in unwashed fish mince and has potential application value.(4)Influence of hydrolysate on the gel properties of unwashed fish mince.The unwashed fish mince,to which a gelatin hydrolysate prepared using flavourzyme and sucrose blend(8g/100g mince,W/W,1:1)was added,had higher gel strength,hardness and chewiness when compared to the control,whereas it is inferior than the quality of unwashed fish mince only added with 8% sucrose.