Preparation of preservative product for Xuong Com Vang longan based on chitosan and the oligochitosan-iodine complex

Abstract

Longan (Dimocarpus longan Lour.) is a tropical fruit characterised by a short shelf life, which necessitates the application of postharvest preservation methods to reduce losses during distribution and consumption. A preservation mixture based on chitosan (CS) and the oligochitosan-iodine (OC-I₂) complex was developed and evaluated for postharvest application in longan fruit storage. Ultraviolet-visible spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy confirmed that 2% H₂O₂ hydrolysis broke the β-1,4 glycosidic bond of CS without altering the OC structure. OC formed a complex with I₂ through -NH₂ and -OH groups. The chitosan-(oligochitosan--iodine) (CS-(OC-I₂)) mixture at 9.00-22.5 g/l extended the shelf life of Xuong Com Vang longan fruits from 5 days (control) to 15-20 days at room temperature. Treated fruits showed reduced respiration rates, microbial density, weight loss, total soluble solids, browning index, and disease index, while maintaining greater fruit hardness and stabilising total soluble solids. These results indicate that the CS-(OC-I₂) mixture is a promising preservative for longan and potentially other fruits, with the capacity to reduce postharvest losses during storage and distribution.