Microbial community analysis of Tarak, a fermented milk product

Microbial community analysis was performed on Tarak, a traditional Korean fermented milk product, by 16S rDNA cloning and pyrosequencing to obtain basic data for the standardization and systematization of the Tarak manufacturing process. Microbial analysis of the prokaryotic community revealed a slight difference in microbial abundance between Bontarak (n) and Tarak (n+1), but Firmicute was dominant at the phylum level. At the genus level, the Lactobacillus and Leuconostoc genera constituted over 90% of the population in Bontarak, but Lactococcus was the dominant genus in Tarak. Bontarak and Tarak showed further differences at the species level. Leuconostoc citreum was the dominant species in Bontarak, constituting 40% of the population. In eukaryotic community analysis, all samples were composed of Ascomycota at the phylum level. At the genus level, Saccharomyces was dominant in Bontarak (85% of the population), while Issatchenkia was dominant in Tarak (95% of the population). At the species level, Saccharomyces cerevisiae was detected at a relative abundance in Bontarak (82%), and Pichia kudriavzevii was the dominant species in Tarak, with a relative abundance of 95%. Sensory evaluation indicated that Tarak had a better appearance and texture than Bontarak. As sweetness was not significantly different between the two samples just slightly higher in Tarak, this was likely due to a significant decrease in sourness in Tarak. These results suggest that the microbial community used affects the quality of Tarak produced. Thus, a stable microbial community must be maintained for the production of Tarak with consistent quality.