Influence of pH, salt and nitrite on the heme-dependent catalase activity of lactic acid bacteria.

A screening of commercial starter cultures used for the production of dry sausage showed a maximum heme-dependent catalase activity in the range of 60 mumol/l hematin for Lactobacillus sake, Lactobacillus plantarum, Lactobacillus pentosus and Pediococcus acidilactici. Pseudocatalase activity was not detected. In standard dry sausage production, 2-3% (w/w) nitrite salt (0.6% sodium nitrite per 100 g NaCl) is normally added, which corresponds to 4-6% salt in the water phase. In vitro experiments with L. sake and L. plantarum have shown that such a high concentration of salt caused a significant reduction of catalase activity and bacterial growth. In the case of P. acidilactici, the catalase activity remained constant at a salt concentration up to 6% (w/w); at 7% (w/w) the activity decreased sharply. The pH also affected the catalase activity, which remained constant up to pH 5.1 and decreased dramatically at lower values. The effect of nitrite has also been investigated. L. pentosus and P. acidilactici were not affected by the addition of 160 ppm nitrite (NO2-); L. plantarum, on the other hand, showed a significantly reduced catalase activity. In practice, optimum fermentation characteristics combined with an optimum catalase activity which are not inhibited by salt concentrations higher than 6% (w/v) and a residual nitrite content of about 160 ppm (w/v), are of the utmost importance in screening and selection of lactic acid bacteria for starter cultures.