Post-acidification of set yoghurt always occurs during cold storage causing short shelf life thus consumer unacceptability.
The short storage life of particular yoghurt affects the consumption level as well. This study concentrated on the inhibitory effect of
preservatives on post-acidification of yoghurt. The set yogurt mixture was produced and inoculated with 2% starter culture containing
Streptococcus thermophilus and Lactobacillus bulgaricus. After the required inoculation; ε-polylysine (as natural preservative) and
potassium sorbate (as chemical preservative) were added separately at different concentrations. Titratable acidity, pH and firmness of
yogurts during cold storage for 20 days were examined. Evaluation of sensory properties was done for the best concentrations of each
preservative. The pH values and titratable acidity were significantly lower (