Document Type : Research Paper
Authors
1 Department of Agriculture, Islamic Azad University, Savadkooh branch, Savadkooh, Iran
2 Department of Agriculture, Savadkooh branch, Islamic Azad University, Savadkooh, Iran
Abstract
Background and objectives: Garlic (Allium sativum L.) has antimicrobial activity due to organic sulfur compounds such as thiosulfates, especially allicin. Considering the environmental hazards and the concern of the potential risk of synthetic additives, the fabrication and use of active biodegradable packaging containing herbal essential oils and extracts in the form of composite films and coatings in the food industry are considered. This study aimed to fabricate and evaluate the mechanical, physical and antimicrobial properties of an active composite film based on polyvinyl-alcohol/chitosan/nanoclay with 2% and 4% concentrations of garlic extract for its prospective applications in food packaging.
Methodology: First, solutions of polyvinyl alcohol (5%), chitosan (2%), nanoclay (4%) through the dissolution of a certain amount of material in solvents, as well as an aqueous extract of garlic, were separately prepared. Then, the films were fabricated using the casting method based on experimental treatments including films based on polyvinyl alcohol, polyvinyl alcohol/chitosan, polyvinyl alcohol /chitosan/nanoclay and polyvinyl alcohol/chitosan /nano clay (montmorillonite) containing concentrations of 2% and 4% garlic extract (5 treatments in total). The mechanical properties of the films include tensile strength (TS), elongation at break (EB), and Young's modulus (YM), which were determined using a texture analyzer, physical properties including thickness were measured using a digital micrometer, and solubility (WS), absorption humidity (WAC), water vapor permeability (WVP) were determined using ASTM standard assay, opacity using a spectrophotometer as well as antimicrobial properties of the film against S. aureus and E. coli using the diffusion disc method was evaluated on mullerhinton agar culture medium. The diameter of the inhibitory zone of bacterial growth was measured and considered as an indicator of the antimicrobial activity of the films. In a completely randomized design with 5 treatments and 3 replications, the data were analyzed using SPSS statistical software by one-way ANOVA. The means were compared using the test Duncan (p<0.05).
Results: The mechanical, physical and antimicrobial properties of the fabricated films were affected by the structural components of the films as well as the concentration of garlic extract. Tensile strength and Young's modulus (about 30 MPa and 0.14 MPa, respectively) were higher in active triple composite films containing garlic extract, at the same time, these films had the lowest value of elongation at break. The addition of chitosan and nano montmorillonite to polyvinyl alcohol-based film and fabricating composite film increased the thickness of the films, such that the triple composite films were thicker (0.17 mm) and more opacity. The lowest value of water absorption and solubility as well as water vapor permeability was seen in active triple composite films. Unlike most of the mechanical and physical properties of films, the antimicrobial effect of active composite films was directly affected by the concentration of garlic extract used. In general, the antimicrobial effect of garlic extract against gram-positive bacteria (S. aureus) was greater than gram-negative bacteria (E. coli). In concentrations of 2% and 4% of garlic extract, the diameter of the inhibitory zone of bacterial growth of Staphylococcus aureus was 21.6 and 26.55 mm, respectively, and Escherichia coli was 16.5 and 19.1 mm, respectively.
Conclusion: Active triple composite film (polyvinyl alcohol/chitosan/montmorillonite) containing 4% garlic extract with lower WVP value, and higher value of TS, TM, and thickness can prevent moisture exchange of food, maintaining the integrity of the packaged product, delaying the spoilage process, thereby, extend the shelf life of the products. Therefore, the enrichment of polyvinyl alcohol/chitosan/nanoclay triple composite biodegradable film with garlic extract can make it a potentially recommendable option for new food packaging with longer storage.
Keywords
Main Subjects
)