Study On Preservation Of Cold Fresh Pork By Polyvinyl Alcohol Film

For prolonging the shelf life of cold fresh pork,this study started with the selection of preservative suitable for cold fresh meat,first selected E.coli and S.aureus as experimental strains of spoilage bacteria of cold fresh pork,studied the inhibition effect of citric acid,chitosan and potassium sorbate on the two experimental bacteria,and then added a certain amount of chitosan,potassium sorbate and citric acid with polyvinyl alcohol(PVA)as the base film preparation solution.PVA film,PVA/chitosan film,PVA/chitosan/citric acid film,PVA/potassium sorbate film and PVA/ potassium sorbate/citric acid film were prepared.The addition amount of chitosan in PVA/chitosan film was determined by single factor test,and the physical properties of PVA/chitosan/citric acid film with different content of citric acid were investigated on the basis of PVA/chitosan film.Under the same experimental conditions,potassium sorbate with the same amount of chitosan was added to the basis solution of PVA to make PVA/potassium sorbate film.On this basis,different contents of citric acid were added to investigate the comprehensive properties of the PVA/potassium sorbate/citric acid film and find out the optimum film ratio.The changes of sensory,included PH,volatile base nitrogen(TVB-N),methemoglobin,acid value and colony count of pork wrapped in film at 0-4? were determined:1.Chitosan,potassium sorbate and citric acid all have some inhibitory effects on E.coli and S.aureus,and their effect is to inhibit the growth and expansion of hyphae.The inhibition effect of two kinds of films soluted withcitric acid was better than that of single chitosan and potassium sorbate preservation solution.2.The best ratio of PVA/chitosan/citric acid film is: 8wt%PVA,the addition of chitosan is 2% of PVA mass,and the addition of citric acid is 7% of PVA mass.3.Under the same conditions,the effect of three films on pork preservation is: PVA/potassium sorbate/citric acid film ? PVA/potassium sorbate film ?PVA/chitosan/citric acid film.4.The morphology and structure of the film were examined by IR and SEM.The analysis shows that a certain amount of chitosan and citric acid can be uniformly dispersed in the PVA/chitosan/citric acid film,and a certain amount of potassium sorbate and citric acid can be uniformly dispersed in the PVA/potassium sorbate/citric acid film.Both film materials have good compatibility and the surface is uniformly dispersed without obvious bubbles.5.Wrapped pork with PVA/chitosan/citric acid film and PVA/potassium sorbate/citric acid film can form a certain confined space and reduce the loss of water,and chitosan and potassium sorbate have a good inhibitory effect on spoilage the bacteria of pork.Both films can inhibit the growth of pork spoilage bacteria,and protect the environment from the infection of other bacteria.