Optimization offermentation parameters for vegetable juices with nitrate content to obtain natural nitrites

Abstract

The aim of this study was to obtain a nitrites-containing juice by fermentation of plant materials that contain nitrates, and finding the best parameters of fermentation to obtain the highest concentration of nitrite. Celery and parsnip vegetable juices were obtained by manually pressing of chopped material plants. Staphylococcus carnosus and Staphylococcus xylosus used for vegetable juice fermentations were isolated and then identified from a starter culture. The nitrate and nitrite concentration (ppm) was determined before and after 20 hours and 30 hours of fermentation at different concentration of NaCl (0, 5.0, 7.5, 10.0, wt. %), different temperatures (4°C, 35°C, 45°C) and different pH value (5.0, 6.0, 7.0) for each composition. For nitrates and nitrites determination, colorimetric methods were used. After 20 hours of incubation at 35°C, in the absence of NaCl and pH 7.0, it was obtained a concentration of 897.3±7.3 ppm nitrites in the presence of Staphylococcus xylosus, comparative with 799.3±6.7 ppm nitrites in the presence of Staphylococcus carnosus. The highest nitrate concentration was determined for raw parsnip juice, while nitrites were not detected in fresh vegetable juices of celery and parsnip. Fermentation formulas without added salt showed the highest concentration of nitrites, optimum temperature for juices fermentation was 35°C, and optimum pH value for juices fermentation was 7.0.