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AbstractStaphylococcus aureusis a gram-positive bacterium, commonly found in the nostrils, on the skin and on the hair of warm-blooded animals, including humans. It can produce a wide variety of virulence factors, including staphylococcal enterotoxins (SEs). In literature, 24 different SEs and many variants have been identified; among these, only five (the so-called classic enterotoxins) have been well-defined. Due to their emetic activity, SEs are frequently responsible for staphylococcal food poisoning, when consumers ingest contaminated food. SEs are proteins with a high tolerance of denaturing and can maintain their activity, even when the vegetative form of the bacteria is inactivated during food processing. The enterotoxin encoding genes are found in a variety of different genetic elements and, as a result, enterotoxin production varies widely between different populations of S. aureus. SEs production is modulated by multiple, and often overlapping, regulatory pathways, which are influenced by environmental factors. Furthermore, complex food matrices possess many characteristics (storage temperature, pH, sugar or salt concentration, presence of competitive microorganisms, etc.) that have a high impact on S. aureusbehaviour. The multiple factors influencing S. aureusgrowth in food matrices and the production of SE complicates risk assessment procedures. In this review, we focus on enterotoxin production by S. aureusin food of animal origin, its regulation and detection and on the most recent developments in predictive microbiology and risk assessment models.HighlightsStaphylococcus aureusproduces several virulence factors that contribute to the pathogenesis of several serious human diseases: among these staphylococcal enterotoxins (SEs) have emetic activity, and are responsible for staphylococcal food poisoning (SFP).SEs are proteins that maintain their activity even though the vegetative form of the bacteria is inactivated during food processing.Enterotoxin encoding genes are found in a variety of genetic elements and enterotoxin production varies and is regulated by multiple regulatory pathways, which are influenced by environmental factors.

AbstractThe aim of this study was to compare the effect of a commercial formulation consisting of natural ingredients and dextrose on the production of salami. We analysed the effect on microbiological, physico-chemical and sensorial properties in the production of nitrite-free swine and roe deer (Capreolus capreolus) salami. Six batches of salami were prepared: four with the addition of starter cultures and diverse substrates (no substrate, skimmed milk, commercial formulation and dextrose) and two without starter cultures as controls (one without substrate and one with skimmed milk). Samples for microbiological and physico-chemical analysis were taken on day 0, day 5 and day 25. A sensory evaluation was performed at the end of the ripening process. The best results regarding the changes in the microbiota were observed in the batch produced with the addition of skimmed milk (final concentration for Pseudomonasspp. was 3.07 ± 1.11 log cfu g−1, for Enterobacteriaceae was 1.57 ± 0.51 log cfu g−1and the total coliforms were undetectable). As regards the sensory evaluation, the best scores (in particular colour uniformity, fat/lean distribution and mould flavour) were assigned to the salami produced with the addition of dextrose. According to the results obtained in this study, the addition of the commercial formulation to manufacture nitrite and nitrate-free, dry-cured swine and roe deer salami led to no significant effects on their microbiological and sensory characteristics. Overall, the results obtained with the addition of the commercial formulation were very similar to those obtained by adding dextrose, which is the main component of the formulation itself.HIGHLIGHTSThe effect of a commercial formulation on microbiological, chemical and sensory characteristics of nitrite-free swine and roe deer (Capreolus capreolus) salami was analysed.The results obtained with the addition of the commercial formulation were very similar to those obtained by simply adding dextrose or just skimmed milk.The use of commercial preparation seems therefore not worthwhile.

The presence of lactic acid bacteria can be detrimental when the abundant growth of slime-producing strains (Lactobacillusspp. and Leuconostocspp.) causes spoilage of meat products. Two strains of lactic acid bacteria were isolated from vacuum-packed cooked hams that had been withdrawn from the market for the so-called ropy slime defect and identified as Leuconostoc mesenteroides. In an attempt to define the behavior of ropy slime–producing bacteria, two strains of L. mesenteroideswere incubated in de Man Rogosa Sharpe broth at different storage temperatures and conditions of thermal abuse (4, 12, 20, 30, 37, and 44°C). Both strains showed a lack of growth at 44°C, a good level of development at 30 and 37°C, and evident growth ability at low temperatures, with a long stationary phase. In particular, the bacterial concentration at 4°C was >105CFU mL−1after more than 120 days of incubation. This study demonstrates that the refrigeration temperature for cooked meat products does not constitute a hurdle for ropy slime producers and their subsequent ability to spoil.

AbstractThree strains of lactic acid bacteria (LAB) and a commercial probiotic were selected to evaluate their in vitroactivity towards Listeria monocytogenes. The strains Lactococcus lactisssp. lactis,strain 340, L. lactisssp. lactis, strain 16; Lactobacillus caseissp. casei, strain 208 and Enterococcus faeciumUBEF-41 were inoculated into skim milk and brain heart infusion broth (BHI) to get an initial Lactococcus: Lactobacillus: E. faeciumUBEF-41 ratio of 2:1:1 and a concentration of approximately 7 log cfu mL−1until challenge vs. pathogen. L. monocytogenesATCC 7644 was also inoculated in same media to get approximately 4 log cfu mL−1. Growth curves in skim milk and BHI at 4, 10 and 30 °C, respectively were studied for: (i) LAB formulation; (ii) L. monocytogenesand (iii) LAB vs. L. monocytogenes. When challenged with LAB, at 30 °C in milk, L. monocytogeneswas not detectable after day-3 and in BHI it decreased below log cfu mL−1after day-5. At 10 and 4 °C, in both media, L. monocytogenescounts were always significantly lower (p < .001) than the counts of L. monocytogenesalone from day-2 for milk at 4 °C and BHI at 10 °C and from day-7 for BHI at 4 °C and milk at 10 °C. In conclusion, the proposed formulation was able to limit L. monocytogenes in vitrogrowth, even at refrigeration temperature.