Production of italian dry salami: effect of starter culture and chemical acidulation on staphylococcal growth in salami under commercial manufacturing conditions.

The effect of starter culture and chemical acidulation on the growth and enterotoxigenesis of Staphylococcus aureus strain S-6 in Italian dry salami under commercial manufacturing conditions was studied. The experimental design included two levels of S. aureus (10 and 10/g), three levels of starter culture (0, 10, and 10/g), three levels of initial pH (pH(0)) (6.1, 5.5, and 4.8), two manufacturing plants, and three replications. S. aureus growth in the salami was affected significantly (P < 0.005) by pH(0), initial levels of S. aureus (staph(0)) and lactic acid bacteria (LAB(0)), day of fermentation, and by the interactions of pH(0) x day, pH(0) x LAB(0), LAB(0) x staph(0), pH(0) x staph(0), and pH(0) x location of fermentation. In general, the lower the pH(0) and the higher the LAB(0), the greater the inhibition of S. aureus. The LAB levels during the fermentation were affected significantly (P < 0.005) by pH(0), LAB(0), day of fermentation, location, LAB(0) x pH(0), and LAB(0) x day. Derived regression equations related level of S. aureus and LAB at any day of fermentation to a number of microbiological and chemical variables. Close similarity of observed and predicted levels of S. aureus and LAB growth demonstrated the usefulness of the experimental approach in evaluating the safety of a process. No detectable enterotoxin or thermonuclease was found at any stage of processing even when S. aureus reached levels of 10/g of salami.