Effect of temperature, water activity, pH and some antimicrobials on the growth of Penicillium olsonii isolated from the surface of Spanish fermented meat sausage

The effect of various factors and compounds used in the manufacturing of 'Cantimpalos chorizo, a fermented meat sausage made in Spain, on the growth of three strains of Penicillium olsonii isolated from the surface of the sausage has been investigated. In addition, one strain of Penicillium nalgio-vense (ATCC 66742), used as starter culture in fermented foods, has been included in the study. Fungi were grown under various ecological conditions (temperature, water activity and pH) and in the presence of the main antimicrobial compounds (sodium chloride, sodium nitrite and potassium nitrate) and spices (paprika, oregano and garlic) that are added to the initial sausage mixture. The effect of different combinations of some of the factors was also investigated. The results showed that at the levels found during the manufacturing of the sausage, the most influencing parameters on the growth of both species were water activity, temperature and sodium chloride. Both P. olsonii and Penicillium nalgiovense were capable of growing at 10degreesC Penicillium nalgiovense and one of the natural P. olsonii strains could also grow at the lowest water activity tested (0.86). However the optimum water activity was higher for both species (0.92 for P. olsonii and close to 1 for P. nalgiovense). The pH, nitrates and nitrites, and the spices tested had no or a very little effect on the growth of both species. Differences among the naturally isolated strains were not significant (P > 0.05) in most experiments. Also, in general terms, the behaviour of our isolates was very similar to the reference strain of P. nalgiovense, which indicates closeness to this species from a technological point of view and suggests the possibility of the use of P. olsonii as starter culture. (C) 2002 Elsevier Science Ltd.