Keywords: edible coatings, modified chitosan, peppermint essential oil, papaya marketability, chitosan coating, papaya fruit quality, postharvest papaya fruit, antifungal agents, peel discolouration, hydrophobicity
Effects of chitosan–based coatings containing peppermint essential oil on the quality of post–harvest papaya fruit
Edible coatings comprised of antimicrobial polymers based on chitosan are promising technologies to preserve post–harvest fruit quality. In this study, we investigated the potential utility of a coating made from chitosan modified by N–acylation with fatty acid to preserve post–harvest papaya quality. Peppermint essential oil (EO) was added to the chitosan–based coatings as an antifungal agent. A formulation which contained a high concentration of peppermint EO (1.0%) without chitosan apparently damaged the peel, resulting in higher peel discolouration, less colour development and lower marketability. The most promising treatment was unmodified chitosan (1%) in combination with peppermint EO (0.2%). The fruits treated with this formulation showed less peel discolouration than the experimental control and 100% of the fruits were marketable. The modified chitosan apparently increased the hydrophobicity of the coating resulting in a loss of firmness and delayed colour development of coated fruits during ripening.