Biodegradable fish gelatin/chitosan-based active films alter chill-stored golden pomfret (Trachinotus blochii) metabolites mainly through modulating four metabolic pathways

Abstract

The high perishability of fish after capture requires effective preservative strategies to delay its quality loss and extend shelf-life of fish products during chilled storage. There has been a growing interest in employing biodegradable active films for chill-stored fish preservation due to the increasing environmental concern of plastic packaging disposal. The aims of this work were to develop fish gelatin/chitosan-based films loaded with nanoemulsified α-tocopherol (α-TP) and thyme essential oil (TEO) and their combination, and to evaluate the effectiveness of the films to inhibit fish quality deterioration. Nanoemulsified biopreservatives were obtained by ultrasonication with desirable polydispersity index. A good compatibility of the nanoemulsions within the film matrix was observed using confocal laser scanning microscopy (CLSM) and their uniform distribution rendered the active films compact and smooth surface morphology as revealed by SEM. FTIR spectra showed that the chemical structure of the films was altered by incorporation of the natural materials. For metabolic profiles in chill-stored fish fillets, totally 47 metabolites were identified using NMR spectroscopy. Amino acid metabolism was found to be the most influenced pathway during fish storage. Besides, the production of some undesirable metabolites such as organic acids, putrescine, tyramine, and hypoxanthine were markedly reduced, which suggested that the active packaging could preserve fish quality through interfering the carbohydrate, nitrogen, and nucleotide metabolisms. Combination of nanoemulsified α-TP and TEO extended the fish shelf-life to 15 days with TVB-N values under the rejection limit, which further confirmed that the biodegradable active films could effectively delay fish quality deterioration.