Synergistic effects of ε-polylysine hydrochloride and gallic acid on Shewanella putrefaciens and quality of refrigerated sea bass fillets

The abundant nutrients of raw sea bass are excellent media for specific microorganisms like Shewanella putrefaciens, which cause fish spoilage. In this study, gallic acid (GA), protocatechuic acid (PA) and chlorogenic acid (CA) were tested for their synergistic antibacterial effects with ε-polylysine hydrochloride (PL). A strong synergistic inhibitory effect against S. putrefaciens was observed in PL and GA treatment. The combination of 1/8 MIC PL and 1/4 MIC GA completely inhibited S. putrefaciens growth and caused cell death. This combination significantly damaged the cell structure, and induced serious leakage of electrolytes, nucleic acid, and protein. GA, PL and PL-GA treatments significantly reduced sensory deterioration, total viable counts, total volatile base nitrogen and thiobarbituric acid value of sea bass fillets during 4 °C storages, with PL-GA showing the best effect. The results suggested that the combination of PL and GA might be an effective preservative to control marine fish spoilage. •ε-polylysine hydrochloride and gallic acid had synergistic antibacterial effects.•Gallic acid can target DNA gyrase of S. putrefaciens in silico.•Their combination at subinhibitory concentration caused S. putrefaciens death.•This combination damaged the cell membrane of S. putrefaciens.•This combination retarded fat oxidation and inhibited S. putrefaciens in sea bass.