Changes of metabolite profiles of fish models inoculated with Shewanella baltica during spoilage

Three Shewanella baltica strains (ABa4, ABe2, BBe1) were inoculated into sterile fish sticks and broths, and the metabolic changes during chilled storage were determined using NMR. Totally 39 metabolites in two fish models were identified, which were involved in four main metabolic pathways: peptide and amino acid, nitrogen, nucleotide, and carbohydrate pathways. In fish sticks, proteins were hydrolysed to increase amino acids (up to 230%) by S. baltica, especially by strain ABa4. In both fish sticks and broths, S. baltica induced the formations of biogenic amines from amino acids and trimethylamine-N-oxide (TMAO), and the degradations of adenine nucleotides to form inosine and hypoxanthine (2- to 4-fold increment). In addition, sugars and lactate were consumed by S. baltica, accompanied with the productions of acetate and succinate. Strain BBe1 showed higher TVB-N and capability of biogenic amine production and nucleotide degradation. The changes could be attributed to the enzymes of S. baltica during growth and respiration. These findings confirm that S. baltica has highly spoilage potential to decompose nutrients in fish, mainly via nitrogen and nucleotide pathways. This study provides insight on controlling seafood spoilage by intervening degradation pathways.