Development of dual-functional packaging system to remove ethylene and release antimicrobial for fresh produce during distribution
Creators: name: Zhang, Yan
Publisher: name: No Publisher Supplied
Year: 2021

description: Before reaching consumers via the global food supply chain, fresh produce is affected by the external environment during distribution, susceptible to quality deterioration induced by ethylene and contamination by microorganisms, leading to food safety issues and tremendous food loss. The package can be a convenient and effective tool to alleviate this problem by creating and maintaining a desirable internal package environment surrounding the fresh produce. To ensure fresh produce quality and safety, the overall objective of this work was to investigate the feasibility of developing a dual-functional package to remove ethylene and release antimicrobials in the internal package environment throughout the journey of the fresh produce in the supply chain. Specifically, a dual-functional package was developed by incorporating metal organic frameworks (MOFs) to adsorb ethylene and using a hydrophilic chitosan-based formulation to release H2O2 and thymol. The scope of the study included three major parts of work. This new dual-functional package could provide the optimum internal package environment to prevent premature ripening, maintain food quality, inhibit microbial growth, and prevent postharvest loss.The first part of this work focused on developing packaging film that can prevent premature ripening or senescence of fresh produce by embedding metal organic framework (MOF) in the food package to remove ethylene. The suitable MOF candidate was identified and embedded in selected polymer materials, the formulation and processing conditions were optimized, and bio-efficacies of the resulting films were tested. Results showed that magnesium formate MOF (MgF) was the best candidate as an ethylene adsorbent. Low-density polyethylene (LDPE) film was extruded by adding 2% of MgF, and the extruded film effectively delayed the banana ripening. The second part of this work focused on improving ethylene removal efficiency by combining chemical reactants with MOF in the package. TiO2 and KMnO4 were mixed with MgF at different ratios, and formulations were optimized to achieve maximum ethylene removal. The optimized formulation was embedded in the package in sachet and coating label forms, and their bio-efficacies were evaluated on bananas and strawberries. Results showed that the performance of the proposed MgF-embedded film could be improved by adding KMnO4 as an oxidizer to achieve a synergistic effect in removing ethylene and 60% more ethylene removal by the optimized formulation could be achieved when triggered by moisture. The sachet and coating label containing optimized formulation could extend the shelf-life of strawberries and bananas more significantly than applying MOF alone.The third part of this work focused on developing an antimicrobial layer that effectively inhibits microbial growth and maintains quality. The antimicrobial layer was developed as a hydrophilic formulation containing H2O2 and thymol as essential antimicrobials. Chitosan was used as a polymer matrix and crosslinked by citric acid to form the structure for antimicrobials incorporation. Results showed that FTIR confirmed modification of chitosan by citric acid, H2O2 and thymol could be stabilized via hydrogen bonds with the matrix, and their release was triggered by moisture in the fresh produce package. The antimicrobial layer formulation was optimized to maximize its antimicrobial efficacy against four pathogenic bacteria Escherichia Coli O157:H7, Salmonella Saintpaul, Salmonella Braenderup, and Listeria Monocytogenes; and two spoilage fungi, including Colletotrichum musae and Botrytis cinerea. The optimized formulation with 3% H2O2 was found the most effective in inhibiting all microorganisms and achieved a synergistic effect using disc diffusion assay. The addition of thymol can help to inhibit fungi more effectively. In bio-efficacy studies by applying the optimized antimicrobial coating in strawberry packages, H2O2 was found to be released sustainably triggered by moisture and help inhibit microbial growth on the surface of strawberries. Antimicrobial packages also helped reduce the weight loss by 3-4%, delayed grey mold growth and strawberry decay by five days. What is more, strawberries in antimicrobial packages were found to maintain higher firmness and slower quality changes than the control group.In conclusion, it is feasible to develop a dual functional package that could (1) remove ethylene to control fresh produce ripening by embedding MOF as ethylene adsorber and (2) release H2O2 and thymol to inhibit microbial growth by developing a chitosan-based antimicrobial coating. The proposed dual-functional packaging system can combine two functional parts in different packaging forms, including sachet, film, or coating. A dual-functional package can also be customized and optimized based on different requirements of fresh produce and distribution conditions to achieve the most extended shelf-life.