Fermentation and microbial characteristics of Korean traditional fermented milk, Tarak

In this study, for modernization of Korean traditional fermented milk, Tarak was made using four kinds of commercial Makgeolli based on the ancient cookbook Suwoonjabbang. Samples of Tarak were periodically collected during 24 h of fermentation at 37°C. After fermentation, changes in pH, titration acidity, and viscosity were analyzed. Fermentation metabolites, including organic acids and free sugars, were analyzed by HPLC. Numbers of yeast and lactic acid bacteria during 24 h of fermentation were measured. The pH of Tarak significantly decreased (P<0.01), whereas its acidity significantly increased (P<0.01) during fermentation. The viscosity increased during 8∼24 h of fermentation until curd was separated in Tarak. The level of ethanol increased from 0.37∼0.52 mg/mL to 0.51∼0.71 mg/mL during 24 h of fermentation. Lactic acid and lactose were the major organic acid and free sugar in Tarak, respectively. The number of lactic acid bacteria increased from 5.23∼6.25 log CFU/mL to 9.87∼10.41 log CFU/mL at the beginning during 24 h of fermentation. The number of yeast increased from 5.14∼6.47 log CFU/mL to 6.99∼7.73 at the beginning during 24 h of fermentation at 37°C. The major strains of Tarak were Pediococcus acidilactici, Lactobacillus fermentun, Lactobacillus curvatus, and Saccharomyces cerevisiae. Therefore, we concluded that Tarak was a fermented milk by both lactic acid bacteria and yeast, which was similar to koumiss or kefir.