Preliminary Investigation on Mandarin Peel Extraction and Development of Functionalized Chitosan-Guar Gum Edible Films Using Response Surface Methodology (RSM)

Every year worldwide, citrus processing generates large volumes of by-products, often wasted, although rich in bioactive compounds. In this study, mandarin peel (Citrus reticulata) was used as a source of functional compounds for the development of guar gum/chitosan functionalized edible films. The response surface methodology was used for both bioactive extraction and edible film formulation. For extraction, the optimization focused on extraction time, solvent composition (acetone/water ratio), and solvent/solid ratio, while for edible film, the guar gum/chitosan ratio, glycerol content, and mandarin peel extract concentration were selected as critical formulation variables. The predictive models exhibited high statistical significance (p < 0.05), adequate predictive ability, and good consistency of predicted and experimental values. The extraction optimization allowed significant results in total polyphenols (329.59 mg GAE/g), flavonoids (42.6 mg QE/g), and total carotenoids (1.53 mg/g) associated with significant antioxidant activity. Mandarin peel bioactive compounds integrated into composite edible film resulted in excellent functional properties in terms of swelling index (65.83%), water absorption (65.48%), weight loss (41.91%) and visual appearance (L* 89.30). These findings support formulating chitosan–guar gum films with mandarin peel bioactives, advancing biopolymer-based approaches toward next-generation sustainable packaging.