Study On The Fresh Keeping Of Portuguese Oyster (Crassostrea Angulata) By Using The Compound Of Polysaccharide From Pullulan

Oysters are delicious and nutritious and are loved by consumers.Among them,the Portuguese oyster(Crassostrea angulata)is cultivated on a large scale in Fujian and its annual output exceeds 1.456 million tons.But due to its(Crassostrea angulata)soft texture and high moisture content,its shelf life is usually only 1 to 2 days,and its freshness rapidly drops down after leaving the water.Pullulan Polysaccharide is a water-soluble viscosity mucopolysaccharide that good at film formation and can block oxygen which can be used for preservation of aquatic products.However,there are fewer applications in actual production,it has not been applied to the preservation of oysters.In order to extend the shelf life of Crassostrea angulata,this experiment developed a pullulan Polysaccharide Based compound and applied it to the preservation of Crassostrea angulata.The experiment first studied the preservation effect of Crassostrea angulata,treated with different concentrations of pullulan Polysaccharide under refrigeration at 4?.By measuring the freshness index(volatile base nitrogen,thiobarbituric acid value)of Crassostrea angulata,the results showed that all the freshness index with the 1.5% pullulan Polysaccharide group was significantly better than blank group,so,the optimum concentration of the polysaccharide is1.0%.Next developed a pullulan Polysaccharide based compounding preservative of Crassostrea angulata.The 1.0% pullulan Polysaccharide and 0.1% bamboo leaf flavonoids,1.5% citric acid,and 0.6% tea polyphenols were separately compounded and stored at different temperatures(4?,-3?,-18?),measuring the freshness index at regular intervals and evaluate the effect of the compounding agent on the preservation of Crassostrea angulata.The results showed that compared with the control group,the shelf life of the compound group could be prolonged by34.05%~44.91% at 4?.The shelf life of the compound group was prolonged by 23.46% to55.18% at-3?.At-18 ? freezing conditions,the compound group can effectively delay the degradation of Crassostrea angulata protein and fat oxidation.Among them,the combination of1% pullulan Polysaccharide + 0.1% bamboo leaf flavonoids and 1% pullulan Polysaccharide +0.6% tea polyphenols had a better effect on retarding protein degradation and fat oxidation,respectively,1% Pullulan Polysaccharide + 1.5% citric acid reconstitution group had the best inhibitory effect on microbial reproduction.With the reduction of storage temperature,the freshness of Crassostrea angulata can be greatly extended.Among them,Crassostrea angulata loses water seriously at-18 ? in the frozen state,so the-3 ? micro-freezing condition is the best storage temperature.Comprehensive analysis confirmed that the tea polyphenols combination group had the best preservation effect on Crassostrea angulata,and all of its indexes were better than the control group.The pullulan Polysaccharide based compound developed in this study can play a positive role in the preservation of Crassostrea angulata at different temperatures and prolong the shelf life of Crassostrea angulata.It also provides a reference for future research on the application of pullulan polysaccharide in the preservation of aquatic products.