A fruit edible coating machine to protect the morphological, physiological, and biochemical properties of citrus fruits

This study aimed at constructing a laboratory machine for chitosan-based citrus fruit edible coating operation. The machine included a roller fruit conveyor system for fruits to travel, where the fruits were sprayed with a conventional coating material. The spraying flow rate and the slope of the device during the spraying were optimized to minimize the changes in morphological (image processing characteristics), physiological (firmness and total soluble solids), and biochemical (limonene and microRNA concentrations) properties of the orange fruits during 16 days of storage period with the minimum consumption of the coating material. In addition to fruit physiological properties such as firmness, fruit biochemical properties including limonene and miR-397 concentration as a regulator of lignin synthesis in oranges were significantly preserved in the fruits coated using the proposed machine. Although morphological and some physiological properties could not reveal the effects of edible coating on fruits due to the short period of storage, the concentration of miR-397, which was measured with a portable electrochemical biosensor at the femtomolar level, could determine the effects of coating treatments on fruit quality with suitable performance. Coated fruits that exerted the least change in miR-397 concentration after 16 days, had a more suitable appearance after two months of cold storage. While, many of the control fruits that showed significant changes in microRNA concentrations after 16 days, were in unfavorable exocarp conditions for the market. The findings of this study are useful for developing new fruit coating machines and introducing microRNAs as early indicators of fruit post-storage quality.