Antifungal activity of a chitosan and polyvinyl alcohol (PVA) mixture on damage-causing strains isolated from postharvest oranges grown in Vietnam

The identification and development of a biofilm that is highly efficacious against disease-causing microorganisms in postharvest fruits are pivotal in ensuring the stability and security of agricultural supply chains. The objectives of the present work were to assess the antifungal ability of a chitosan and polyvinyl alcohol (PVA) mixture on postharvest oranges using the agar-well diffusion method, and to determine the minimum inhibitory concentration of the mixture. Four fungal species responsible for causing damage and rot in oranges were isolated from oranges namely Penicillium sp., Aspergillus niger, Rhizopus delemar, and Colletotrichum sp. Overall, the chitosan and PVA combination showed antifungal activity against the four strains, but the composition at which inhibition was maximised depended on the fungal species tested. The minimum inhibitory concentration of the chitosan/PVA mixture against the four isolated fungal strains was 1.15% chitosan + 0.39% PVA, 0.83% chitosan + 0.56% PVA, 1.1% chitosan + 0.37% PVA, and 0.41% chitosan + 0.41% PVA for Penicillium sp., A. niger, R. delemar, and Colletotrichum sp., respectively. These results are expected to aid in further developments on the management of postharvest spoilage during storage of fruits and vegetables.