Effects of nitrates and nitrites on Lactobacillus helveticus and Lactobacillus casei dairy cultures

Abstract

The aim of this work was to observe the effects of nitrites and nitrates on the titratable acidity of milk after addition of Lactobacillus helveticus (TX 121) and L. casei (CAD 154) dairy cultures and on the levels of nitrate and nitrite. After adding L. helveticus and nitrites the increasing concentrations of the latter brought about a marked decrease in titratable acidity. In milk containing 100 mg·kg–1 nitrite the resulting concentration was 39.33 mg·kg–1 NaNO2. Nitrates caused a less obvious decrease in titratable acidity, giving 13.27 g·l–1 lactic acid. In milk containing 100 mg·kg–1 NaNO3 the resulting concentration was 24.99 mg·kg–1 NaNO3. Experiments with L. casei and a nitrite additive revealed a decrease in titratable acidity to 8.89 g·l–1 lactic acid. After incubation, nitrite levels were reduced from 100 mg·kg–1 NaNO2 to 37.81 mg·kg–1 NaNO2. Nitrates were also stated to inhibit the titratable acidity of the sample, which decreased to 11.42 g·l–1 lactic acid. Nitrates were reduced to 46.99 mg·kg–1 NaNO3. The present study shows that nitrites, more than nitrates decrease the titratable acidity of milk after addition of L. helveticus and L. casei dairy cultures. A reduction of nitrates and nitrites in milk samples by Lactobacillus was also found. The results of this study can be used in the dairy industry in the production of several types of hard cheese as well as fermented milk products that use L. helveticus and L. casei dairy cultures.