Background. The aim of the study was to determine the effect of the addition of magnesium gluconate and citrate on the physicochemical properties, the number of bacterial cells and the organoleptic properties of cow’s and goat’s milk fermented by Lactobacillus acidophilus.
Results and conclusions. The fortification of milk with magnesium gluconate and citrate had a  significant effect on the active acidity of milk before fermentation. After the addition of magnesium compounds and repasteurization of processed milk, the pH value of the milk decreased. The addition of magnesium compounds (gluconate and citrate) did not differentiate active  acidity in the goat’s milk fermented by Lactobacillus acidophillus LA-5 on the 7th day of cold storage. The opposite relationship was shown for the fermented cow’s milk. The content of lactic  acid, apart from the magnesium compound used, was also affected by the type of milk used. The fermented goat’s milk was characterized by a higher content of lactic acid compared to the  fermented cow’s milk. The addition of gluconate and magnesium citrate increased the syneresis level of probiotic fermented milk. The highest syneresis was shown in the goat’s milk with  magnesium citrate. Enriching milk with magnesium gluconate significantly shaped the color parameters of the resulting fermented milk, which was characterized by a darker color. In all  groups, the milk was characterized by the share of yellow and green colors. However, the level of their intensity was significantly different, depending on the type of milk and the magnesium  compound used. In the fermented goat’s and cow’s milk, the number of Lactobacillus acidophillus LA-5 cells above 8 log CFU∙g^-1 was found, which means that the resulting fermented milk  meets the criterion for classifying it as a probiotic product.