Chitosan- Bidens pilosa Extract-Based Coating with Enhanced Free Radical Scavenging, Antifungal, and Water Barrier Properties: Metabolite Profiling, Film Characterization, and Raspberry Preservation

Chitosan (Ch) was functionalized with Bidens pilosa (BP) extract at 1, 3, or 5% to form Ch-1 BP, Ch-3 BP, and Ch-5 BP, respectively. Ch without plant extract was used as a control. The composite films were characterized and tested for antifungal properties in the agar disc diffusion approach and antioxidant capacity in the 2,2-diphenyl-1-picrylhydrazyl assay. Chitosan films fused with B. pilosa extract inhibited the growth of P. expansum with a 10 mm inhibition diameter compared to control films (3.33 mm). Ch-1 BP exhibited the highest (79.13%) radical scavenging activity (RSA), and control films had the lowest RSA (50.97%). Liquid chromatography-mass spectrometry analysis identified 20 metabolites, including phenolic acids (9), organic acids (8), monosaccharides (1), amino acids (1), flavonoids (1), and six unknown polyphenols. Chitosan-based composite coating (Ch-1% BP) exhibited the lowest weight loss percentage (16.74%) and decay incidence (17.3%), while the untreated fruit showed higher weight loss and decay incidence (48.33% and 83.2%, respectively). The effectiveness of chitosan-enriched coating in maintaining the postharvest quality of raspberry fruit suggests that this plant could be a postharvest agent for controlling microbial spoilage and protecting against oxidative stress, ultimately resulting in extended storage in horticultural crops.