Study On Low-Temperature Storage Quality Changes And Green Processing Technology Of Grass Carp(Ctenopharyngodon Idella)

Freshwater fish are recognized by consumers because of their affordable price and good taste.Grass carp(Ctenopharyngodon idella),as an important species in China's freshwater fish industry,is a fast-growing freshwater fish with high nutritional value.At present,due to the development of cold chain logistics,online shopping,and changes in consumer groups,the past fresh sales methods have been gradually replaced by cold chain logistics fish fillet products.Grass carp has high protein content and is susceptible to microbial contamination to cause spoilage and deterioration.Therefore,research on the use of appropriate green processing technology for grass carp sliced products has become an urgent problem to be solved.In this paper,grass carp is divided into grass carp fillets and heads.Two different storage methods,cold storage and frozen storage,are used,and the effect of new coating preservation methods on the quality of grass carp fillets under4?cold storage and different quick freezing are studied.The effect of different packaging methods and methods on the quality of grass carp head frozen storage at-18?.1.The effect of a new method of coating preservation on the quality of frozen grass carp fillets at 4?was studied.Three experiments were set up in the experiment of chitosan quaternary ammonium salt coating group,chitosan quaternary ammonium salt compound mint extract coating group and blank control group.With physical and chemical indexes,protein oxidation indexes,microbial and sensory indexes and correlation analysis to determinate the influence of the quality change of different coating materials to grass crap fillets of refrigeration.The two coating materials can effectively inhibit protein deterioration in the early stage of storage.According to the sensory score and the quality deterioration evaluation indicators,the chitosan quaternary ammonium salt compound mint extract coating group and the chitosan quaternary ammonium salt coating film can extend the shelf life of refrigerated grass carp fillets by 4.5 days and 3 days,respectively.The electronic nose combined with sensory(odor)score shows that both coatings can effectively inhibit the deterioration of the odor of grass carp fillets,while chitosan quaternary ammonium salt compound mint extract coating group was more significant.The use of chitosan quaternary ammonium salt as a coating material can effectively increase the shelf life of frozen grass carp fillets,and at the same time improve the characteristics of chitosan that is only soluble in dilute acid and insoluble in water and its limited antibacterial properties.Further extending the shelf life,at the same time helps to improve the coating material's inhibitory effect on fat oxidation and improve the inherent odor of grass carp.2.The effect of different freezing methods on the quality of frozen grass carp head was studied.Three groups of experiments were set:liquid nitrogen quick freezing group,flat plate quick freezing group and cold storage freezing group,parameters as physical and chemical indexes,protein oxidation indexes were collected.These indexes measures the effect of different freezing methods on the quality changes of frozen grass carp heads at-18?.The results showed that the two groups of quick-frozen groups had significant differences in physical and chemical indexes during the whole storage process and protein-related indexes in the early stage of storage compared with the cold storage freezing group(P<0.05).The liquid nitrogen quick-freezing group and flat-plate quick-freezing group were stored to the 16th week.Compared with fresh samples,the TBARS value of the cold storage group and the cold storage group increased by 63%,91%and130%(P<0.05),and the K value increased to 47.07%,53.74%and 64.62%(P<0.05).After 2 weeks of storage,the myofibrillar protein content in the liquid nitrogen quick-freezing group,flat-plate quick-freezing group,and cold storage freezing group decreased by 3.5%,7.0%,and 10.5%compared with fresh samples,respectively(P<0.05).After 4weeks of storage,Ca²⁺-ATPase activity decreased by 53.03%,70.48%and 72.82%,respectively(P<0.05).These results showed that compared with direct freezing in cold storage,quick freezing can effectively delay the deterioration of frozen grass carp heads,and the effect of liquid nitrogen quick freezing is better than that of flat quick freezing.3.The quality changes of flat-plate quick-frozen grass carp heads with different packaging methods were studied.Three groups of experiments were set:vacuum packaging group(VP),ice-plating combined with air packaging group(GAP),and air packaging group(AP),with physical and chemical indexes,protein oxidation indexes,microbial indexes collected to indicate the effects of different packaging methods on the quality changes of flat-frozen grass carp heads.The results showed that the TBARS values of the VP group,GAP group,and AP group increased by 98%,66%and 102%,respectively(P>0.05),compared with the TBARS value of fresh samples at 16 weeks of storage.At the 8th week of storage,the K values of the VP group,GAP group and AP group increased to 36.71%,49.74%and50.74%,respectively(P<0.05),and the myofibril protein content decreased by 12.37%,10.31%and 14.95%respectively compared with fresh samples(P<0.05).The total number of colonies in the VP group,GAP group,and AP group reached 4.56 lg(CFU/g)4.74 lg(CFU/g)and 4.77 lg(CFU/g),respectively,after storage until the 16th week.The VP group was significantly lower than the GAP group and AP group(P<0.05).These results illustrated that the combination of ice coating and air packaging and vacuum packaging can slow down the quality deterioration of grass carp heads caused by the extension of freezing time to varying degrees.Among them,the ice coating treatment has a significant effect on inhibiting fat oxidation,while the vacuum packaging has a better antibacterial effect.In sum,the paper adopts the refrigeration and freezing processing methods used in daily storage and transportation,and divides grass carp into two kinds of common products in the market,grass carp flakes and grass carp head.Comprehensive biological preservation,quick-freezing technology and common packaging methods in the market for systematic research to determine the appropriate green processing methods for grass carp,providing theoretical guidance and technical support for actual production and utilization.