Biological effect in Kimchi

There are several factor affect bacteria in vegetable in Kimchi and in our bodies.

Osmosis, which the reaction occurring at the first stage of making kimchi, kills bacteria living in the vegetable, as dehydration of the bacteria happens.

Activity of microorganisms or enzymes is also affected by the acidity and the salt concentration.

In general, under the acidic conditions, the activity of bacteria becomes less active and stops below pH 3.0.

One experiment shows that the number of Escherichia coli (E.coli) decreased with the decrease in pH as the fermentation prodressed at pH 4.5 and the acidity of 0.22%. 

The same trends were observed at different temperatures. If pH is below 3.9 then no E. coli was detected, and the times taken to reach pH 3.9 were 20 days at 5° C, 15 days at 10° C and 2 days at 30° C, meaning that the reaction occurred faster at higher temperature. 

The number of total bacteria rose as fermentation proceeded and then the number of total bacteria decreased below pH 3.5 (acidity ca. 1.0 %). Intestinal pathogenic bacteria, such as Clostridium perfringens ATTC 13124, Listeria monocutpgenes ATTEE 19111, salmonella typhimurium KCTC 1625, Staphylococcus aures KCTC 1621, Vibrio parahaemolyticus ATCC 27519 and Escherichia coli O157:H7 ATCC 43894 were not detected at pH below 4.1, 3.7, 3.8, 3.8, 3.7, 3.7 respectively. The results provide the evidence of safety of Kimchi.