Kimchi fermentation in permeable Korean earthenware Onggi

Since ancient times, Korean chefs have fermented foods such as kimchi, gochujang, and soy sauce in traditional fermentation vessels called Onggi.  Onggi are purported to provide gas permeability which facilitates the growth of lactic-acid-forming bacteria.  In this experimental study, we perform time-lapse videography and carbon dioxide measurement in various fermentation vessels, including Onggi.  Counter-intuitively, we find that the permeable wall of Onggi does not restrict the growth rate of bacteria but can limit their maximum number. The porosity thus acts as a safety valve for bacteria growth, which may have been used in preventing over-fermentation.