Traditional Kimchi Tool Onggi Works Better for Fermentation [Study]

Kimchi has become very popular nowadays. According to a new study, the traditional Korean banchan of salted and fermented vegetables is best produced using the traditional tool onggi.

Onggi Is Best For Kimchi

Soohwan Kim, a mechanical engineering Ph.D. student specializing in fluid mechanics and biophysics at the Georgia Institute of Technology, and his doctoral adviser, Georgia Tech fluid dynamicist David Hu, studied kimchi's fermentation process. They combine experimentation and mathematical modeling to produce the results, Scientific American reported.

According to them, producing kimchi using onggi enables more bacterial growth than sealed jars. Maria L. Marco, a food microbiologist at the University of California, Davis, initially wondered why fermentation produces different flavors despite the same ingredients and recipe. Her question was answered - the tool matters.

Marco wasn't involved in the study. She finds it interesting that the process of fermentation affects the food.

The permeability of the containers, or how quickly liquid and gas may move through them, makes them different from one another. Kim claims that to make exceptional kimchi, fermentation vessels must be in a semipermeable state instead of too permeable or impermeable. Their experiment showed that onggi was the best vessel.

They are constructed of eco-friendly materials and have been scientifically designed. One of Korea's top 100 cultural symbols is Onggi ceramics, according to Korea.net.

Why Onggis Is The Best Kimchi Vessel?

Permeability affects the delicate dance between carbon dioxide and lactic acid bacteria. These bacteria flow naturally from the soil to the growing plants, including the cabbage and other components that make up the foundation of kimchi.

Lactic acid and other bacteria proliferate during the salty fermentation process and release carbon dioxide, accumulating in the container. Results from the study show that lactic acid bacteria "proliferate in a moderate carbon dioxide level," according to Kim. However, extra carbon dioxide needs a place to go, or it will build up to a point where it interferes with the growth of vital bacteria. On the other hand, if the container is excessively permeable, too much carbon dioxide will escape, and fewer bacteria will thrive.

Kim had purchased an unglazed onggi from his homeland on Jeju Island, South Korea, for the experiment. Each jar underwent three tests, and before each test, the containers were sterilized in an autoclave. The onggi was fitted with a specially constructed lid that could house pressure, carbon dioxide, and oxygen sensors to allow for precise measurements. They filled any openings between the sensors and the top with a thin plastic film. The glass jar leaked a little, but not as much as the onggi, as Kim and Hu discovered in their investigation.

The glass jar and cabbage-filled onggi were placed in an oven set to 25 degrees Celsius for two days for each trial. Kim increased the temperature above normal to hasten the fermenting process. Despite the fact that kimchi can be fermented at much lower temperatures, like five degrees C, the researchers believed the only difference brought on by the greater temperature is a faster reaction time.

Lactic acid bacteria flourished because the onggi released carbon dioxide more quickly than its glass counterpart. The gas prevented bacterial development in the glass jar because carbon dioxide wasn't released as quickly there.

According to the research team's publication, the onggi's porous structure is similar to the loose soil where lactic acid bacteria are naturally present. It ensures that the food fermented in the container is teeming with bacteria.

The experiment, inspired by Korean tradition, was used by the researchers to highlight the onggi's permeability. They filled the vessel halfway with salt water, and salt crystals formed on its outside within eight hours.

Kim cites the term "salt flower" from Korean culture. Usually, this phenomenon is seen when Korean chefs ferment ganjang, or soy sauce, in onggi. It is believed that the presence of these saline blossoms on the exterior of an onggi is a sign that it can produce superior sauces.

The study was published in the Journal of the Royal Society Interface.

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