Impact of Prangos Ferulacea on Some Microbial, Physicochemical and Sensory Properties of Probiotic Low Fat Yogurt Containing Lactobacillus Casei

The Prangos ferulacea (PF)–yogurt is a traditional food in Iran. This study investigated the effects of PF on the microbial, physicochemical and sensory properties of probiotic yoghurt. Pasteurized low fat milk was heated up to 85°C, cooled to 40°C, and then mixed with conventional and Lactobacillus casei starter cultures incubated at 37°C until pH decreased to 4.6. Then, the cooked PF was added to yogurt and stored at 5°C for 21 days. Acidity, Syneresis, probiotic colony count and sensory evaluation of yoghurt was determined during the storage time. The experiments were replicated for three times. Probiotic yogurt (PY) was examined as the control and probiotic yoghurt containing 10, 20 and 30% Prangos ferulacea (PFY) as the samples. Total titratable acidity of PFYs compared to PY was not significant during 21 days. The syneresis rate of PFY yogurt showed significant differences compared to PY during storage time (P<0.001). Comparison of the mean scores of sensory attributes (taste, odor, syneresis, mouth feel and color) of PFY yogurt showed that there were no significant differences with PY. Enumeration of lactobacillus casei (logCFU/mL) revealed significant differences in PFYs compared to PY in each experimental day (P=0.040). At the end of the storage time (day 21), the highest number of L.casei was observed in PY and PFY 20% and the lowest in PFY30%. Adding Prangos ferulacea (20%) to probiotic yogurt prevented an increase in acidity, a decrease in syneresis rate and an increase in the number of probiotic bacteria during 21 days. Results showed that the highest number of probiotic bacteria was seen in probiotic yogurt containing 20 percent Prangos ferulacea; probably, the existing fiber and some nutrients in Prangos ferulacea promoted the viability of probiotic bacteria.