An Exploratory Study on Spoilage Bacteria and Listeria monocytogenes in Fresh Salmon: Extending Shelf-Life Using Vacuum and Seasonings as Natural Preservatives

SIMPLE SUMMARY: The study aims at improving the shelf-life and safety of fresh salmon, a highly perishable food often consumed raw in sushi or sashimi. Good hygiene practices and vacuum packaging extended shelf-life up to 20 days. The presence of the bacteria Carnobacterium maltaromaticum inhibited Listeria monocytogenes growth, which may be responsible for foodborne illnesses. Seasonings, namely oregano oil, lemon juice, garlic powder, and salt (NaCl), showed inhibitory effects on spoilage bacteria and L. monocytogenes. The seasonings’ mixtures also exhibited bacteriostatic and bactericidal effects. Finally, a medium produced from salmon was developed and it showed a good correlation with bacterial growth in a standard commercial culture medium. ABSTRACT: A growing population increases the demand for food, but short shelf-lives and microbial hazards reduce supply and increase food waste. Fresh fish is highly perishable and may be consumed raw, such as salmon in sushi. This work aims to identify strategies to improve the shelf-life and safety of fresh salmon, using available methods (i.e., vacuum) and exploring the use of natural preservatives (i.e., seasonings). Vacuum packaging and good hygiene practices (which reduce initial flora) extended shelf-life up to 20 days. Carnobacterium maltaromaticum was dominant in vacuum packaging conditions and showed potential for inhibiting Listeria monocytogenes. For natural preservatives, L. monocytogenes required higher inhibitory concentrations in vitro when compared to the 10 spoilage bacteria isolated from fresh salmon fillets, presenting a minimum inhibitory concentration (MIC) of 0.13% for oregano essential oil (OEO), 10% for lemon juice, 50 mg mL(−1) for garlic powder, and >10% for NaCl. A good bacteriostatic and bactericidal effect was observed for a mixture containing 5% NaCl, 0.002% OEO, 2.5% lemon juice, and 0.08 mg mL(−1) garlic powder. Finally, using the salmon medium showed an adequate correlation with the commercial culture medium.