Study On Absorbent Film Prepared By Corn Straw For The Preservation Of Cold-fresh Meat

At present, the proportion of the tray cold-fresh meat sold in the domestic supermarket in the consumption of fresh meat is increasing year by year. But there will be a lot of extract juice soaking from the cold-fresh meat in the long period of storage and this would affect the sensory quality of the cold-fresh meat, make the relative humidity of the microenvironment in the packaging tray reach to 96%, cause a lot of fluid to gather in the surface of the cold-fresh meat, which is called'sweating', with the sensory quality reduced. At the meanwhile, it's so easy for microbe to breed that the shelf life of the cold-fresh meat reduces and the time of the cold-fresh meat as the first-class fresh meat is 3 to 4 days.Corn straw as an agricultural by-product contains a lot of cellulose, which can be used as functional materials. This thesis tried to extract cellulose from corn straw in the way of chemical-bio combined degumming and had gained short-track cellulose Fibers whose purity were over 97%. Then they were made into super absorbent polymer (SAP), which had a inverse suspension polymerization and could satisfy the meet of absorpting fresh meat extract juice which was a complex electrolyte. It could be seen that the cellulose SAP formed gel after absorpting the extract juice from the SEM photograph. The extract juice was in the three-dimensional structure of modified cellulose polymer and the absorption rate to simulated blood was up to 104g/g. At the meanwhile, cellulose SAP could reach saturated absorption in 20 minutes from its initial absorption rate 35g/g·min-1. but as the extract juice soaked slowly from the cold-fresh meat in its storage, the soaking rate in 12h was 2.8×10-5 g/g·min-1, the super absorbent polymer as a film met the condition fully. The biodegradability of the cellulose SAP was tested using spore bacillus and it was found that the SAP certainly had biodegradability and it could be degraded about 15% in 30 days. This provided the basis for continued development.As two antimicrobial finishing agents to fibrous materials, chitosan-citric acid and chitosan-Ag+ were prepared to nap the artificial cellulose fibre, which was achieved by modifying the corn straw cellulose by sulfonation. It was found that the antimicrobial effect of fibre dealed with the antimicrobial finishing agent of low molecular weight (11,000) chitosan was better than the antimicrobial finishing agent of high molecular weight (190,000) chitosan and both had a good antimicrobial effect when the usage of antimicrobial finishing agent was 6% and 8%. Loose corn straw cellulose was processed into outer cellulose-based film by the technics of meal pulp flow into network which was used as handi wrap of the tray cold-fresh meat after rolling and combining organically with SAP, antimicrobial fibre and cellulose-based film.As the film which contains the cellulose SAP had absorpted the fresh meat extract juice, too large relative humidity (RH%=97) in packaging tray could be avoided and the humidity would be maintained at the appropriate level(RH%=87), which would not lead to the'sweating'of the cold-fresh meat caused by too high humidity in micro-environment of packaging. It could be seen from the determination of the cold-fresh meat's freshness degree that the quality of the tray cold-fresh meat could be better maintained after adding the film to the tray and it would not lead to the decline of cold-fresh meat'sensory quality because of the soaking of fresh meat extract juice in its long storage in freezer, which could maintain the cleanliness of the shelves and make the cold-fresh meat be sold well. The time of the cold-fresh meat as the first-class fresh meat is 6 to 7 days and the time of the cold-fresh meat as the second-class fresh meat is 2 to 3 days, generally, it would become inferior meat after 12 days. But it would become inferior meat after 9 days if the film wasn't added into the tray and the time of the cold-fresh meat as the first-class fresh meat is generally 3 to 4 days. So, comparing with the tray cols-fresh meat without adding the film, the time of the cold-fresh meat as the first-class meat with adding the film had extended 3 days.