Effects of Shallots (Allium stipitatum) aqueous and ethanolic extracts on the Streptococcus thermophiles and Lactobacillus bulgaricus in TSB medium and yogurt.

The aim of this study was to investigate the effect of ethanolic and aqueous extracts of shallot on the survival of yogurt starter bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus). Aqueous and ethanolic extracts of shallots were extracted by soaking in distilled water and ethyl alcohol. Then MIC and MBC extracts were obtained for yogurt starter bacteria by microdilution method. Aqueous and ethanolic extracts were added to pasteurized milk at concentrations obtained in the MIC test along with 3% yogurt starter. The inoculated milk was incubated at 45 ° C until pH = 4.4 for 2 hours. After that, the yogurts were cooled to 4 ° C Then, on days 1, 3, 7, and 14, pH, acidity, and LAB count tests were performed on yogurt samples. The results showed that on days 1, 3, 7, and 14, the acidity and pH of the aqueous extract groups were significantly different to the ethanolic and control groups (p <0.05). Also, the lactic acid bacteria count test on days 1, 3, 7, and 14, the aqueous and ethanolic extract groups were significantly different from the control group (p <0.05). The results also showed that the inhibitory effect of aqueous extract of shallot was more on yogurt starter bacteria than ethanolic extract of shallot (p <0.05). In coclussion the revealed that the starter bacteria in yogurt in presence of Shallot extracts were alive and active until day 14 during refrigerator storage, which can transmit the probiotic effects of yogurt and shallots to the consumer.