THE FATE OF SPOILAGE AND PATHOGENIC BACTERIA IN FERMENTED SAUCE-BASED SALADS

The risk that fermented sauce-based salads may cause microbial food poisoning is determined by a number of factors, namely contamination of the ingredients, growth and toxin production during the first stage of fermentation, and inactivation during fermentation or storage. To investigate the possible growth and persistence of spoilers and pathogens, salads were inoculated with Klebsiella pneumoniae, Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus and fermented with lactic acid bacteria. A rapid decrease of pH, in addition to a low final pH (< 4.2) were necessary to inhibit the growth and survival of Klebsiella pneumoniae. Growth or survival of B. cereus in cabbage salads fermented with different starters was not detected. In leek-cabbage-ham salads, which were inoculated with S. aureus (420 cfu g-1) and fermented at 45°C with Lactobacillus spp., S. aureus increased 5 to 6 generations, after which the numbers declined. In salads that were composed of ingredients with lower buffering capacities, less growth occurred. When L. monocytogenes Scott A was inoculated in cabbage salads, which were then fermented with different strains of Lactobacillus spp., 2 to 3 generations of growth occurred during fermentation, followed by a rapid decline to undetectable levels. Inhibition of spoilage and pathogenic bacteria was due largely to the production of organic acids and a decrease in pH. Primarily, measures should be taken to attain absence or low initial contamination with these pathogens. Proper hygienic care during processing should also be assured. © 1993 Academic Press Limited.