Studies On Performance Of Chitosan Based Activity Packaging Films And Applications In Food Storage

With increasing concerns on food safety and food packagings, active food packagingshave been developed in recent years to ensure safety of foods, maintain food quality andextend shelf life of foods. Currently, one of the research hotpoints for active packagings is toprepare food packagings by using natural renewable and biodegradable materials and endowthe packagings new functions through adding functional additives, such as antioxidants,antibacterial agents and nutrition, etc.Chitosan, a natural carbohydrate copolymer yielded from deacetylation of chitin, is abiodegradable, biocompatible, and non-toxic polysaccharide. Due to its antimicrobialactivity, chitosan has a great potential for applications in food packaging. Although chitosanis a promising biopolymer for active food packaging, it does not have significant antioxidantactivity and has narrow antibacterial spectrum. These weaknesses limit its applications.Improvements of antioxidant activity and antibacterial activity could expand applications ofchitosan in active food packagings.In this thesis, tea polyphenols (TP) and honeysuckle flowers extract (HFE) were used asadditives, chitosan/TP films, chitosan/HFE films and chitosan/TP/HFE composite films wereprepared through casting method aiming at enhancing the antioxidant activity andantimicrobial activity of chitosan films. The properties related to food packaging of theprepared chitosan based films were characterized. The prepared chitosan based films wereapplied to storages of soybean oil and spiced beef to investigate their actual effectiveness.The results of this study could provide basic data and technical support for developingchitosan based active food packagings.Chitosan films incorporated with different amounts of TP were prepared. The results showed that the antioxidant activity of the chitosan/TP films increased with increasing of TPconcentration, but the antioxidant activity of the chitosan/TP films declined with time due tooxidation of phenolic compounds in the films. After the addition of TP, moisture barrierperformance of the chitosan/TP films was significantly increased. With increasing of TPconcentration, the antimicrobial activity, mechanical properties and transparence of thechitosan/TP films decreased, while swelling ratio and solubility increased. Meanwhile, theincorporation of TP gave rise to the films red-brown appearance.Chitosan films incorporated with different amounts of HFE were prepared. The resultsindicated that the ability to inhibit Escherichia coli of the chitosan/HFE films wassignificantly enhanced. After the addition of HFE, antioxidant activity and moisture barrierperformance of the chitosan/HFE films were significantly increased. But, the antioxidantactivity of the chitosan/HFE films was lower than that of the chitosan/TP films. Withincreasing of HFE concentration, mechanical properties, swelling ratio, and transparence ofthe chitosan/HFE film declined, while solubility increased. Meanwhile, the incorporation ofHFE gave rise to the films taupe appearance.Chitosan films incorporated TP and HFE at different ratios were prepared. The resultsshowed that antioxidant activity of the chitosan/TP/HFE composite films increased withincreasing of TP proportion, while the antimicrobial activity of the chitosan/TP/HFEcomposite films increased with increasing of HFE proportion. When the ratio of TP to HFEwas1:1, the chitosan/TP/HFE composite films have higher tensile strength, elastic modulusand water vapor permeability as well as lower solubility. With decreasing of TP proportionand increasing of HFE proportion, elongation at break, swelling ratio, and transparence ofchitosan/TP/HFE composite films declined.The chitosan based films were used for soybean oil storage to investigate effectivenessof preserving soybean oil from oxidation. The results showed that the chitosan based filmscan effectively inhibit oxidation of soybean oil. The effectiveness of inhibiting oxidation forthe chitosan based films follows the order: chitosan/TP/HFE composite films> chitosan/TPfilms> chitosan/HFE films> chitosan film. Incorporation TP and HFE into chitosan has synergetic effect in enhancing antioxidant activity of chitosan. For the chitosan/TP/HFEcomposite films with different ratios of TP:HFE the effectiveness of inhibiting oxidationfollows the order:5:1>3:1>1:1>1:3>1:5, in which TP plays important role.The chitosan based films were used to preserve spiced beef. It was found that sampleswrapped with chitosan based composite films (chitosan/TP, chitosan/HFE, andchitosan/TP/HFE) showed lower changes in odor, discoloration, slime formation, overallacceptability and less microbial growth than those wrapped with chitosan film and controlone. The fresh-keeping effectiveness of chitosan based composite films follows the order:chitosan/TP/HFE composite films> chitosan/HFE film> chitosan/TP film> chitosan film.Incorporation TP and HFE into chitosan has synergetic effect in inhibiting microbial growthand extending the shelf life of the spiced beef. For the chitosan/TP/HFE composite filmswith different ratios of TP:HFE, the fresh-keeping effectiveness for spiced beef follows theorder:1:5>1:3>1:1>3:1>5:1, in which HFE plays important role.