Effects of Chitosan Coating on the Storability and on the Ultrastructural Changes of 'Jonagold' Apple Fruit in Storage

Abstract

Chitosan is a high molecular compound, containing nitrogen derived from the shell of crab and shrimp. The effects of chitosan coating on respiration, ethylene production, and storage of 'Jonagold' apples (Malus pumila Mill. var. domestica Schneid.) were investigated. Coating the fruit with chitosan significantly reduced the respiration rate and ethylene production in storage. Postharvest coating increased the internal CO₂, and decreased the internal O₂ levels of the fruits markedly. Firmness of the treated fruits were considerably retained during storage. Observation by SEM revealed that the chitosan films covered overall surface of the treated fruits. A plenty of deep cracks were observed on the pericarp of uncoated fruits, but much less on the surface of coated fruits. Growing hyphae, which was resulted from an inoculation of conidia of apple gray mold caused by Botrytis cinerea, were recognized on the pericarp of uncoated fruits, whereas many deformed spores were observed on the surface of the coated fruits. These observations support the view that chitosan coating could not only suppress the ethylene production and respiration, but also inhibit conidial germination and fungal development resulting in preserving the quality of 'Jonagold' apples.