According to Table 1, viable counts of probiotics in all treatments stored at 5°C had no significant changes during storage (p < 0.05). For example, the VPI (Table 2) for all strains at the end of storage ranged between 0.95-0.97. However, for treatments stored at 20°C, the viable counts of probiotics showed significant decrease during storage. This decline varied among probiotic species because of different sensitivity to environmental stresses such as low pH and high titratable acidity. Considering Table 2, the most survivability throughout the storage in treatments stored at 20°C belonged to L. rhamnosus HN001, L. paracasei Lpc-37, L. acidophilus LA-5 and B. Lactis Bb-12, respectively. B. Lactis maintained only 60% of its initial viable population at the end of storage, whilst this amount was 81% for L. rhamnosus. Scharl et al. (25) demonstrated that the number of living probiotic bacteria in yogurt decreased dramatically after exposure to room temperature.