Nitratų ir nitritų kiekio kitimas pieno rauginimo metu

Abstract

The aim of this paper is to determine changes in the content of nitrates and nitrites in the process of milk culturing. During the culturing of milk samples the amounts of nitrates and nitrites tended to decrease. At the end of the culturing process (after 8 hours) the amount of nitrites decreased by 42,5%, and nitrites by 34%. It was concluded that the content of nitrates and nitrites could be expressed by the two stages, which depend on the quantities of milk acid. At the first stage, which continued for 2-3 hours, slight decrease of the level of nitrates and nitrites was obtained. Further, at the second stage, the level of nitrates and nitrites decreased significantly, while the level of milk acid showed the tendency to increase significantly. In the process of milk culturing the possible transformation between nitrates and nitrites and vice versa has been established. It was observed that nitrates and nitrites had negative influence on the quality and formation of curd structure. Addition of nitrates prolonged the process of formation of curd structure by 9-12% and increased the separation of they by 5-7,5% compared to control samples. Besides, the structure of the curd became less stable.