African Journal of Agricultural Research Vol. 2(8), pp. 365-369, August, 2007

ISSN 1991- 637X­© 2007 Academic Journals

Full Length Research Paper

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

Samira Yeganehzad, Mostafa Mazaheri-Tehrani and Fakhri Shahidi

Food Science and Technology Department, Ferdowsi University of Mashhad, Iran.

*Corresponding author. E-mail: yeganehzad@yahoo.com

Accepted 2 August 2007

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^oC and stored at 4^oC. 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^oC. This work shows the importance of total solid concentration of milk on survival probiotic strains, physiochemical and sensory properties of yoghurt.

Key words: probiotic yogurt, total solids, probiotic survival, physiochemical properties, sensory properties.