Application Effect Evaluation Of Chitosan-Tea Polyphenols Coating On Dry-Cured Grass Carp

Cured fish is a traditional aquatic craft food in China,which is loved by consumers because of its unique flavor.Traditional cured fish often use natural fermentation and sun drying,which takes a long time and the quality is unstable.The lipid oxidation of cured fish continued during storage because of the high content of unsaturated fatty acids.Excessive lipid oxidation not only affects the quality of cured fish,but also accompanies the risk of food safety.In this study,using grass carp as raw material,dry-cured grass carp was made and the effect of different hot air drying temperature on the quality of grass carp was analyzed.Secondly,the effect of chitosan concentration on chitosan-tea polyphenols coating solution and film was discussed.Finally,chitosan-tea polyphenols coating solution was applied on the surface of cured grass carp,and the application effect of chitosan-tea polyphenols coating on grass carp was evaluated by tracking the relevant indexes of grass carp during storage.The results are as follows:1.The effects of different hot air drying temperatures at 35℃and 45℃on the quality of cured grass carp were studied.The results showed that with the final moisture content of45±1%as the standard,the drying time at 35℃was 20 h and the drying time at 45℃was15 h.After drying,there was no significant difference in whiteness and texture between the two groups(P>0.05).The p H value of cured grass carp dried at 45℃was significantly higher than that at 35℃,and the sensory quality was better than that at 35℃.2.To explore the effect of different chitosan concentrations on chitosan-tea polyphenols coating solution and film.The results showed that the concentration of chitosan was positively correlated with the viscosity of chitosan-tea polyphenols coating solution and the thickness of the composite film,and negatively correlated with the water vapor transmittance and oxygen transmittance of the composite film.The results of DPPH radical scavenging rate showed that the DPPH free radical scavenging rate of chitosan-tea polyphenols coating solution with different concentrations of chitosan was more than 90%,and there was no significant difference among the groups(P＞0.05).Fourier transform infrared spectroscopy showed that there was a strong combination between chitosan and tea polyphenols.Comprehensive analysis,1.50%is the best concentration of chitosan.3.Evaluate the application effect of chitosan-tea polyphenols coating on cured grass carp according to the dynamic analysis of related indexes during storage.Through the analysis of quality index,it was found that the L~*value and b~*value of cured fish were significantly lower than those of the control group during storage,but the a~*value changed little,and the whiteness value of the coating group at the end of storage was significantly lower than that of the control group.During storage,the rising rate of volatile base nitrogen and non-protein nitrogen in the coating group was lower than that in the control group,and the deterioration rate of sensory quality in the coating group was lower than that in the control group.Through the analysis of lipid oxidation index,it was found that the peroxide value,carbonyl value,diene value,thiobarbituric acid value,acid lipase activity and phospholipase activity of the coated wax grass carp were significantly lower than those of the control group during storage.On the 28th day of storage,the peroxide values of the control group and the coating group were 0.76 g/100g and 0.31 g/100g,respectively,and the inhibition rate of the coating group on the peroxide value of cured fish was 59.21%.The value of thiobarbituric acid increased at first and then decreased during storage.On the28th day,the values of thiobarbituric acid in control group and coating group were19.34±1.61 mg/kg and 16.06±0.98 mg/kg,respectively,and the coating group was 3.28mg/kg lower than control group.In summary,cured grass carp reached the requirement of water content after drying at45℃for 15 h,and the product quality was better.Chitosan-tea polyphenols composite coating solution of 1.50%chitosan concentration was suitable to be used as the coating solution of cured grass carp.Chitosan-tea polyphenols composite coating can delay the lipid oxidation rate of cured fish during storage and reduce the deterioration rate of product quality.This study provides a method and related theoretical basis for improving the stability of cured fish during storage.