Gelatin-kappa-carrageenan-based edible film incorporated with ethanol extracts from Premna microphylla Turcz leaves for preservation of sailfish fillets

This study proposes to develop edible films (EF) by modification of gelatin/kappa (κ)-carrageenan (KCAR) as a base formulation while incorporating the Premna microphylla Turcz leaf (PMTL) extracts. PMTLs were extracted via distilled water or 95% ethanol (1:20 ratio, w/v) to investigate the content of bioactive substances and evaluate their antioxidant and antimicrobial capacities. The PMTL ethanol extract (PEE) showed satisfactory antimicrobial and antioxidant performance compared to the water extract (PWE). Therefore, different ratios of PEE (0, 5, 10, and 15%) were incorporated into the basic formulation of EF supplemented with the plasticizing agent glycerol (0.5 and 1%) to prolong the shelf-life of sailfish fillets (SF). Incorporating PEE into EF formulations may change the color from transparent to yellow-green, which improves EF's moisture content, solubility, swelling degree, and hydrophilicity. PEE's total phenolic content (TPC) and total flavonoid content (TFC) provided EF with antioxidant capacity, causing EF with predictable mitigation of sharp variation in pH, total plate count, thiobarbituric acid reactive substances (TBARS) value, and histamine content during the storage period of SF (12 days at 4°C). Altogether, this study indicated that EFs manufactured by PEE would be potential candidates for application in food preservation to improve food safety.