Natural Plant Products as Preservatives in Active Food Packaging

Abstract

Spoilage of food is common amongst both developing and industrialized nations. Contaminated food would result in a waste of food resource, can cause serious illnesses, and financially burden food manufacturing companies. The aim of this project is to improve shelf life of food products by preventing fungal growth using plant-based preservatives incorporated into active packaging. We started with literature review on a wide range of plant-based extracts and essential oils known to have antimicrobial activities. Based on the cost and availability of these products, seventeen potential preservatives were obtained for testing. Initial screening for antifungal activity followed standard protocols published for antimicrobial susceptibility testing (AST) using a broth microdilution assay. This method provided inhibition cut-off values and fungicidal values against target fungal strains. Thermal stability profiles were obtained for all plant samples using thermogravimetric analysis (TGA), as heat treatment is unavoidable in the process that manufactures food packaging. Results from AST and TGA provided a baseline to select five potential preservatives for heat treatment. To ensure these five samples were still active post-treatment, they were re-tested with the AST protocol. Finally, the two best candidates were selected to be incorporated into polyethylene plastic films. A standard protocol for plastic testing was followed to determine whether antifungal activities were still present for films. Alongside this test, chemical and mechanical tests were conducted on films to ensure eligible leachability of the antifungal from the film and that film strength was unaffected. AST screening of seventeen extracts identified which samples were able to kill target fungal strains. Thermal stability profiles provided information on which samples were suitable for heat treatment. Five samples were selected, heat-treated and most retained antifungal activities. The best two extracts were tested in plastic films and showed varied preliminary results with only one extract film confirmed to have fungicidal activity against one fungal strain. In summary, this project explored a wide variety of plant-based products that could be used as food preservatives whether incorporated in food or its packaging. Although further testing is required to confirm activity of packaging films, the information gained from this work is invaluable for future research