The influence of lactic acid on listerias in fisch products

The objective of work was to evaluate the effect the lactic acid has on the growth of Listeria in fish products and to give recommendations to manufacturers. Samples used for testing: cold-smoked salmon, cold-smoked mackerel, salted herring, salted salmon. Samples were selected from consumer’s shelf. In the laboratory the antibacterial effect of lactic acid on L. monocytogenes was tested, using different concentrations of lactic acid: 1%, 3%, 5% and 7%. The resistance was evaluated by spiking salmon, mackerel and herring products. The active acidity, organoleptic properties and the acceptance of lactic acid were also evaluated. The analysis showed that the 7% and 5% solutions of lactic acid had the best antimicrobial effect, at their mean value of sterility zone of 7.5 mm and 5.5 mm which was significantly different from other cases, when p≤0.05. The 1% solution of lactic acid was antimicrobiologicaly inactive and had no effect to the growth of L. monocytogenes. Samples of salmon, mackerel and herring treated with 3% lactic acid solution had the best organoleptic characteristics. The number of L. monocytogenes bacteria decreased already 24 h after treatment with 1%, 3%, 5% aqueous solutions in salmon, mackerel and herring samples, kept both in the atmosphere and in vacuum; the change in numbers was greatest in the period of 14 days in comparison with control samples (p