COMPARATIVE-STUDY ON SOME FERMENTATION PROPERTIES OF STREPTOCOCCUS-THERMOPHILUS AND LACTOBACILLUS-ACIDOPHILUS IN MILK AND MODIFIED MILK MEDIA .2. EFFECT OF THE INCREASED SOLID NOT FAT ON THE FERMENTATION PROPERTIES OF THE MIXED CULTURE

Growth and acid production of the mixed culture of Streptococcus thermophilus and Lactobacillus acidophilus were investigated in milk and modified milk media as a function of the solid not fat content. The microorganisms were grown on sterilized cow's milk, cow's milk + 1% glucose and cow's milk + 6% tomato juice media, containing 8.5, 10.34 and 12.18% solid not fat (controlled by addition of skim milk powder). Fermentations were run at 45 degrees C temperature with 3% starters. Results showed that addition of 1% glucose or 6% tomato juice to the cow's milk had a slight stimulatory effect on the growth and acid production of the mixed culture. Increase of the solid not fat up to 12.18% in milk media does not affect the cell counts and acid production significantly but decreases the whey syneresis in the fermented yoghurt-like products. The sensory quality of the fermented products proved to be the best in the case of the fermentation of cow's milk with addition of 1% glucose, containing 10.34% solid not fat.