Figure 1.

(a) Onggi depicted in a mural at Anak Tomb No. 3 from Goguryeo Kingdom (37 BC–AD 668). Image courtesy of the Northeast Asian History Foundation. (b) Top view of kimchi inside an onggi before (left) and after (right) fermentation. (c) Side view of kimchi fermented in a glass jar for 7 days at 30°C. Scale bar 30 mm. The process of interest is the lactic acid fermentation driven by two species of anaerobic bacteria, Lactobacillus and Leuconostoc. A dramatic volume increase and the formation of carbon dioxide bubbles were observed within 1 day.