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 r ange of 60 mu mol/l hematin for Lactobacillus sake, Lactobacillus plan tarum, Lactobacillus pentosus and Pediococcus acidilactici. Pseudocata lase 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 ex periments with L. sake and L. plantarum have shown that such a high co ncentration of salt caused a significant reduction of catalase activit y and bacterial growth. In the case of P. acidilactici, the catalase a ctivity remained constant at a salt concentration up to 6% (w/w); at 7 % (w/w) the activity decreased sharply. The pH also affected the catal ase activity, which remained constant up to pH 5.1 and decreased drama tically at lower values. The effect of nitrite has also been investiga ted. 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 fermenta tion characteristics combined with an optimum catalase activity which are not inhibited by salt concentrations higher than 6% (w/v) and a re sidual nitrite content of about 160 ppm (w/v), are of the utmost impor tance in screening and selection of lactic acid bacteria for starter c ultures.