Chitosan biocoatings formulation by blending, plasticization, and crosslinking methods for their potential fresh produce packaging applications

This study aims to formulate chitosan biocoatings (1.5%) (w/v) by blending (chitosan), plasticization with glycerol (CG), crosslinking using sodium tripolyphosphate (CT), and a combination of plasticization-crosslinking (CGT) methods. Biocoatings were evaluated to study the influence of formulation methods. Physicochemical characterization of biocoatings was performed by SEM, ATR-FTIR, XRD, TGA, and rheological analysis. SEM micrographs revealed a rough morphology of chitosan biocoatings (blending), improved smoothness in CG, heterogeneity in CT, and smoothness in CGT biocoatings. Moderate crystallinity (53.2%), UV-blocking property (94.46 ± 1.06%), and the highest transparency (87.56 ± 0.46%) of CGT biocoatings may provide balanced flexibility, barrier properties, and thermal stability (Tmax ~270 ºC). CGT biocoatings showed boosted antioxidant activity (12.7 ± 0.41%) and superior antimicrobial activity against B. cereus and S. aureus, with zones of inhibition of 17.5 ± 0.5 and 15.5 ± 0.5 mm, respectively, compared to E. coli (10.9 ± 0.79 mm) and P. aeruginosa (15.4 ± 0.6 mm). Antifungal activity of CGT biocoatings (33.4 ± 0.39%) was also found to be higher than that of other biocoatings. Rheological analysis showed that CGT biocoatings displayed commendable structural and flow characteristics by reducing viscosity and shear stress with shear rate. Comparative analysis of biocoatings formulated by different methods revealed that the plasticization method formed flexible coatings, crosslinking enhanced thermal stability and compactness, while plasticization-crosslinking enhanced the antimicrobial and antioxidant properties. Formulated biocoatings might potentially contribute towards United Nations Sustainable Development Goals (SDGs), mainly 2, 3, 7, 12, and 13, ensuring food safety, mitigating postharvest losses, and limiting plastic and energy consumption.