Synergistic Effect of Composite Chitosan/Phenylalanine Edible Coating on the Postharvest Bioactive Composition of Mandarin Fruit

This study investigates the effects of Chitosan and Chitosan/Phenylalanine (Phe) edible coatings on the postharvest quality of mandarins during shelf life at room temperature (21°C) and during cold storage (5°C). Mandarins were treated with Chitosan, Phe, and a combination of Chitosan/Phe, with untreated mandarins serving as a control. Several key quality parameters, including total polyphenolic content (TPC), total flavonoid content (TFC), antioxidant activity (DPPH and ABTS assays), organic acids, and aroma compounds were analyzed at multiple time points. Chitosan and Chitosan/Phe improved glossiness and effectively preserved mandarins by lowering the decay rate and modulating bioactive composition. Chitosan and Chitosan/Phe treatments showed similar outcomes on bioactive composition but Chitosan/Phe treatment was found to be favored. Chitosan/Phe is the most effective treatment, extending mandarin shelf life by maintaining superior nutritional, antioxidant, and sensory quality up to 12 days at room temperature and 35 days under cold storage. Chitosan/Phe coating after 12 days of shelf life significantly reduced weight loss in mandarins, while Chitosan treatment was comparable to Phe and control samples. Additionally, relative to the control, Chitosan/Phe had the most pronounced effect on TPC after 35 days of cold storage with an increase of up to 78.98%, while Chitosan coating resulted in a 40.93% increase, respectively. Chitosan/Phe coating effectively increased TFC (narirutin and hesperidin content) after 12 days of shelf life by 42.79% compared to the control. Organic acids, especially oxalic and citric acids, were positively affected by the Chitosan and Chitosan/Phe coatings, contributing to delayed senescence. Furthermore, the Chitosan/Phe treatment was associated with enhanced volatile compound retention, improving the mandarin aroma profile, particularly in cold storage. Overall, both Chitosan and Chitosan/Phe treatments improved nutritional and sensory quality while reducing fruit decay, but Chitosan/Phe was able to reduce fruit weight loss after shelf life making this combination a more effective solution to extend the shelf life and marketability of mandarins.