Methods
2.2.1. Acid tolerance test of LABs
The MRS medium was adjusted with lactic acid to pH 4.0 and pH
3.5 respectively. The LABs to be tested were inoculated in the pH
4.0 and pH 3.5 MRS broths respectively and then cultivated at 37 ◦C
for 24, 48 and 72 h. The survived LABs was counted and expressed
as colony forming units (cfu). Its survival rate was defined as the
ratio of survived LAB population to initial LAB population.