Influence of Phenylalanine and Chitosan Edible Coatings on the Metabolism of Mandarin 'chahara' – Impact on Bioactive Compounds, Organic Acids and Enzymatic Activity

Satsuma mandarins (Citrus unshiu Marc.) are renowned for their delicate taste, distinct flavor and high nutritional value. However, their perishable nature necessitates innovative preservation methods. Edible coatings have shown promise in improving fruit quality and extending shelf life, but their metabolic effects remain poorly understood. This study investigates the impact of coatings prepared with Chitosan, and a combination of chitosan and phenylalanine (Chitosan/Phe), compared to the use of a phenylalanine dipping solution (Phe), on mandarin metabolism during 21 days of cold storage. The analysis included total polyphenolic and total flavonoid content, antioxidant activity, total proteins, and organic acids in mandarin fruit. Enzymatic activity and malondialdehyde levels were also assessed in mandarin peels. Significant differences were observed among treatments regarding bioactive compounds, organic acids, enzymatic activity, and malondialdehyde levels. Notably, Phe-treated mandarins showed increased bioactive compounds and organic acids content, as well as antioxidant activity, compared to the control. Chitosan or Chitosan/Phe coatings resulted in the highest polyphenol oxidase and catalase activity, while Phe and Chitosan treatments resulted in the lowest malondialdehyde levels at the end of the storage period. These findings highlight the potential of Phe and chitosan-based coatings in enhancing mandarin bioactive profile, antioxidant activity and enzymatic regulation.