Extraction and characterization of biodegradable bioplastic from the red seaweed Gelidium sesquipedale and its application for fresh‐cut apple preservation

BACKGROUND This study evaluated the extraction, macromolecular characterization, and active packaging application of polysaccharides derived from the red seaweed Gelidium sesquipedale for fresh‐cut apple preservation. RESULTS Thermo‐alkaline extraction (20 g kg −1 NaOH, 60 °C), yielded 380 g kg −1 of an agarose rich galactan fraction. High‐performance liquid chromatography–refractive index detection confirmed high d ‐galactose (684 ± 12 g kg −1 ) and 3,6‐anhydro‐ l ‐galactose (261 ± 8 g kg −1 ) contents, validating successful alkali‐induced desulfation down to 5.2 g kg −1 sulfates. Fourier transform infrared spectroscopy further confirmed the characteristic agarobiose repeating backbone. The formulated active film plasticized with 100 g kg −1 glycerol exhibited robust mechanical integrity and a favorable water vapor permeability (1.75 × 10 −6 g m −1 s −1 Pa −1 ). When evaluated as an active insert liner for the preservation of fresh‐cut apples over 12 days at 4 °C, the film significantly reduced cumulative weight loss (37.6 vs 133.2 g kg −1 for control) and maintained headspace gas equilibrium. Furthermore, the active packaging effectively inhibited polyphenol oxidase activity by 53.8%, reduced ascorbic acid degradation by 41.2%, and preserved fresh‐cut apple color by retarding enzymatic browning. CONCLUSION Gelidium sesquipedale galactans demonstrate high performance as a sustainable active packaging matrix, providing an effective, clean‐label strategy to inhibit postharvest enzymatic browning and extend fresh‐cut produce shelf life.