Physicochemical properties of chitosan/zein/essential oil emulsion-based active films functionalized by polyphenols

This study aimed to develop chitosan/zein/essential oil emulsion-based active films functionalized individually by three different types of polyphenols (tea polyphenols, propolis flavones and grape proanthocyanidins). The nature of chemical interaction of these phenolic compounds with other components, zein and chitosan, in particular, and the effect of presence of these polyphenols on the physicochemical, antioxidative and antimicrobial properties of resulting films were evaluated. The water vapor barrier property, tensile strength and flexibility, water repellence and thermal stability of the films were found to be substantially improved in the presence of these phenolic compounds; particularly in the presence of propolis flavones. These polyphenols interacted with other components of films through covalent and hydrogen bonding and helped to form more compact and homogeneous film structure. The films containing phenolics also showed higher ability to inhibit growth of foodborne pathogens and spoilage bacteria. The phenolics containing films also showed strong free radical scavenging ability compared to the control films. The polyphenol containing films also reduced total viable counts, thiobarbituric acid reactive substances, total volatile basic nitrogen values and preserved the firmness of pork when packed in them. This study shows that polyphenol containing films can be suitably used to extend the shelf-life of pork.