• Journal of Dairy Science and Biotechnology
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• v.39 no.3
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• pp.121-127
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• 2021

Yogurt is produced by bacterial fermentation of milk and contains lactic acid bacteria (LAB), which produce various metabolites such as organic acid, hydrogen peroxide, and bacteriocin. This study aimed to investigate cell-free supernatants (CFS) of LAB isolated from Tibetan yogurt. CFS (TY1, TY2, TY3, TY4, TY5, TY6, and TY7) from selected strains of LAB were co-incubated with four different foodborne pathogenic bacteria, namely E. coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, and Staphylococcus aureus. Inhibition of foodborne pathogenic bacterial growth was not affected in the presence of CFS (pH 6.5). In contrast, CFS without neutralization completely inhibited the growth of the bacteria. Furthermore, when the concentration of CFS (without neutralization) was changed to 1:4 and 1:8, a difference in inhibition was observed between Gram-positive and Gram-negative bacteria. CFS more effectively inhibited the growth of Gram-negative E. coli O157:H7 and S. Typhimurium than Gram-positive L. monocytogenes and S. aureus. These results suggest that organic acids in LAB may inhibit the growth of foodborne pathogenic bacteria, particularly Gram-negative bacteria.

• Journal of Korean Medical classics
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• v.27 no.1
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• pp.67-76
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• 2014

Objective : Tarag refers to fermented milk, which has been recognized as daily food of summer in nomadic culture. Also, tarag is cleary defined as a fermented milk product in most of east Asian medical texts. When it comes to tarag-juk described in Korean medical texts, however, there is no definite distinction between milk porridge and tarag-juk. This paper is aimed at finding out whether tarag was merely meaning milk in Joseon. Method : Historical documents of related historical stage, Tibetan and East Asian medical texts, and some cookbooks are mainly consulted, as well as other sources that contains the perception of tarag in Korean history. Result : Tarag is documented as fermented milk in the medical texts of herbs, while tarag-juk is defined as milk porridge in some medical texts in Korea. In one of the Mongolian-Korean dictionary of 18C, milk tea is explained as tarag tea. Conclusion : Although there is not much evidence to back up this conclusion with satisfaction, it would not be to much to say that conception of tarag met some changes from yogurt to boiled milk during Joseon dynasty.