Effects of gelatin/chitosan/Zanthoxylum bungeanum essential oil composite coating on microbial composition and metabolite profiles in refrigerated mandarin fish (Siniperca chuatsi)

Our previous study demonstrated that a gelatin/chitosan/ Zanthoxylum bungeanum essential oil (GE/CS/ZEO) composite film effectively delayed spoilage in refrigerated mandarin fish ( Siniperca chuatsi ). However, the underlying microbial and metabolic mechanisms responsible for its preservative efficacy remain unclear. In this study, high-throughput sequencing coupled with untargeted metabolomics was employed to characterize the core microbiota and metabolic profiles of mandarin fish treated with the GE/CS/ZEO composite film during refrigerated storage. The results showed that the GE/CS/ZEO composite film significantly suppressed the relative abundances of Acinetobacter and Pseudomonas in mandarin fish fillets. At the later stage of refrigerated storage, the predominant genera in the TM-15 group were Acinetobacter , Aeromonas , Vagococcus , and Shewanella . Untargeted metabolomic analysis yielded 2,449 metabolic features, among which the differential metabolites were predominantly glycerophospholipids, bitter-tasting amino acids and their derivatives, amines, nucleotides, and coenzymes. These differential metabolites were significantly enriched in 17 metabolic pathways ( p < 0.05), with purine, phenylalanine, tryptophan, and tyrosine metabolism emerging as key metabolic pathways associated with quality deterioration in mandarin fish during refrigerated storage. Correlation analysis further revealed that Acinetobacter and Chryseobacterium were closely associated with tryptophan metabolism, whereas treatment with the GE/CS/ZEO composite film markedly reshaped the metabolic associations of Aeromonas , resulting in significant correlations with nicotinamide and inosine. Collectively, these findings provide mechanistic insights into the preservative action of the GE/CS/ZEO composite film and highlight the critical roles of microbiota–metabolite interactions in regulating spoilage-related metabolic changes, thereby providing a theoretical basis for the development and application of edible active films for the preservation of refrigerated fish.