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In this study, biodegradable films were developed based on chitosan (CH) enriched with thyme essential oil (TEO) with various additives including zinc oxide (ZnO), polyethylene glycol (PEG), nanoclay (NC) and calcium. Chloride (CaCl2) and to characterize post-harvest kale quality when refrigerated. The results show that incorporation of ZnO/PEG/NC/CaCl2 into CH based films significantly reduces water vapor transmission rate, increases tensile strength, and is water soluble and biodegradable in nature. In addition, CH-TEO-based films combined with ZnO/PEG/NC/CaCl2 were significantly effective in reducing physiological weight loss, maintaining total soluble solids, titratable acidity, and maintaining chlorophyll content, and showed lower a*, inhibiting microbial growth. , appearance and organoleptic qualities of cabbage are preserved for 24 days compared to LDPE and other biodegradable films. Our results show that CH-based films enriched with TEO and additives such as ZnO/CaCl2/NC/PEG are a sustainable, environmentally friendly, and effective alternative for preserving the shelf life of cabbages when refrigerated.
Synthetic polymeric packaging materials derived from petroleum have long been used in the food industry to ensure the quality and safety of various food products. The advantages of such traditional materials are evident due to the ease of production, low cost and excellent barrier properties. However, the massive use and disposal of these non-degradable substances will inevitably exacerbate an increasingly serious environmental pollution crisis. In this case, the development of environmental protection natural packaging materials has been rapid in recent years. These new films are non-toxic, biodegradable, sustainable and biocompatible1. In addition to being non-toxic and biocompatible, these films based on natural biopolymers can carry antioxidants and therefore do not cause any natural food contamination, including leaching of additives such as phthalates. Therefore, these substrates can be used as a viable alternative to traditional petroleum-based plastics as they have similar functionalities in food packaging3. Today, biopolymers derived from proteins, lipids and polysaccharides have been successfully developed, which are a series of new environmentally friendly packaging materials. Chitosan (CH) is widely used in food packaging, including polysaccharides such as cellulose and starch, due to its easy film forming ability, biodegradability, better oxygen and water vapor impermeability, and good mechanical strength class of common natural macromolecules. ,5. However, the low antioxidant and antibacterial potential of CH films, which are key criteria for active food packaging films, limits their potential6, so additional molecules have been incorporated into CH films to create new species with appropriate applicability.
Essential oils derived from plants can be incorporated into biopolymer films and can impart antioxidant or antibacterial properties to packaging systems, which is useful for extending the shelf life of foods. Thyme essential oil is by far the most studied and used essential oil due to its antibacterial, anti-inflammatory and antifungal properties. According to the composition of the essential oil, various thyme chemotypes were identified, including thymol (23-60%), p-cymol (8-44%), gamma-terpinene (18-50%), linalool (3-4%). %) and carvacrol (2-8%)9, however, thymol has the strongest antibacterial effect due to the content of phenols in it10. Unfortunately, the inclusion of plant essential oils or their active ingredients in biopolymer matrices significantly reduces the mechanical strength of the obtained biocomposite films11,12. This means that packaging materials and plasticized films containing plant essential oils must be subjected to additional hardening treatment to improve the mechanical properties of their food packaging.
Post time: Oct-25-2022