Preparation And Analysis Of Pullulan Polysaccharide-antioxidant Coating And Its Effect On The Storage Quality Of Wet-cured Silver Carp

The cured fish has a unique aroma and high nutritional value,but it is prone to oxidation and deterioration during storage,leading to deterioration of quality.In this study,a pullulan polysaccharide(PU)-antioxidant edible film solution with good antioxidant and barrier properties was prepared,and coated on the surface of wet-cured silver carp to investigate the effect of the coating on the quality deterioration of the cured fish during storage.The main research content is as follows:1.Evaluate the antioxidant activity of five commonly used antioxidants: Namely tertbutylhydroquinone(TBHQ),butylated hydroxyanisole(BHA),propyl gallate(PG),tea polyphenols(TP)and rosemary extract(RE),from three aspects: lipase inhibition,lipoxygenase(LOX)inhibition and free radical scavenging.Lipase is the key enzyme in the hydrolysis of fish fat,and its sources include endogenous and exogenous(microbial lipase production,exogenous addition of lipase)two ways.Among the five antioxidants,PG and TP had good inhibitory activity on endogenous lipase of silver carp.TP had the best inhibitory effect on lipase produced by microorganisms(Staphylococcus xylosus,Sx-135),and PG and TP showed better inhibitory activity on exogenous addition of lipase.LOX is the key enzyme causing lipid oxidation.PG showed the highest LOX inhibition rate,and the LOX inhibition rate of PG at the concentration of 5 mg/m L was as high as 87.307±3.843%.The DPPH free radical scavenging activity of synthetic and natural antioxidants were ranked as follows: PG > TBHQ > BHA,RE > TP.After comprehensive evaluation,PG,TP and RE were selected from the five antioxidants for further study.2.Preparation,analysis and application effect evaluation of PU-antioxidant film(liquid):Five kinds of edible films(liquid)were prepared with PG,TP,RE,PG/TP(1:1),PG/RE(1:1)and PU,respectively.Through related performance tests,combined with the application effect study in fish oil and vegetable oil,the antioxidant and barrier properties of the five kinds of films(liquid)were comprehensively evaluated.The results show that adding RE and PG alone increases the pore space between the film matrix and reduces the barrier performance of PU film.However,PG/TP(1:1)incorporated with PU matrix through hydrogen bond and electrostatic interaction,improve the uniformity and compactness of the film,and make the film have good antioxidant activity and barrier performance.The comprehensive analysis shows that PU-PG/TP has high free radical scavenging rate,the best water and oxygen resistance,and can significantly inhibit the hydrolysis and oxidation rate of fish oil and vegetable oil.3.Effects of PU-PG/TP coating on storage quality of wet-cured silver carp: The PUPG/TP coating solution was applied to the surface of cured silver carp to evaluate the effect of coating on the deterioration of cured silver carp quality during storage.PU-PG/TP coating could reduce the peroxide value,diene value and carbonyl value,thiobarbituric acid value of cured silver carp during storage.After 28 days of storage,the peroxide value of the film coating group was only 34.950% of that of the control group.The lipase activity and LOX activity of the coating group were lower than those of the control group.The results showed that PU-PG/TP coating could effectively delay the lipid oxidation of cured silver carp during storage.In addition,film coating could delay the decline of p H value,moisture content and sensory score of the fish during the storage period.After 28 days of storage,the sensory score of the film coating group was 10.304% higher than that of the control group.In conclusion,the prepared PU-PG/TP film(liquid)has good antioxidant and barrier properties,and it can effectively inhibit the speed of lipid oxidation and improve the storage quality of cured silver carp.