Studying microbial, physiochemical and sensory properties of directly concentrated probiotic yoghurt

Skim milk with 8.5% total solids was concentrated to 15 and 20% total solids by vacuum evaporation and inoculated with probiotic Lactobacillus. Yoghurts were incubated at 42 degrees C and stored at 4 degrees C. Survival of Lactobacillus, physiochemical (pH, acidity, synersis, and hardness) and sensory properties (taste and texture) of probiotic yoghurts were evaluated every 7 days to 21 days. Results showed that, increasing the total solid concentration of milk increased the survival of Lactobacillus acidophilus, acidity and hardness of yoghurt and reduced the pH and synersis. However, the survival of probiotic Lactobacillus decreased throughout the storage period at 4 degrees C. This work shows the importance of total solid concentration of milk on survival probiotic strains, physiochemical and sensory properties of yoghurt.