An ancient staple of Korean cuisine, kimchi is traditionally fermented in handmade ceramic jars called ‘kimchi’. OMG. However, when it comes to mass production, companies use jars made of materials such as glass to ferment a large amount of kimchi. Now, a new study reveals why some kimchi makers still rely on traditional techniques. OMG It provides the perfect environment for the growth of lactic acid bacteria, the “good” microorganisms that give kimchi its unique sour taste.
“The active growth of bacteria is nutritionally beneficial, [the] It’s the unique taste of fermented foods,” says Soohwan Kim, Ph.D. in mechanical engineering. Student majoring in Fluid Mechanics and Biophysics at Georgia Tech. last month, Royal Society Interface Journal, Kim and his colleagues OMG Experiments with glass jars showed that the same fermentation time produced kimchi with higher levels of lactobacillus in ceramic jars. “There are cultural beliefs: OMG Food tastes better when it’s used in fermented foods, but there’s no good science on that,” says Kim. His work aims to change that.
Making delicious kimchi is an artistic, scientific and culinary endeavor in which the fermentation process is key. Kimchi and other fermented foods are tricky because many different factors affect the process, says Maria L. Marco, a food microbiologist at the University of California, Davis. “Among certain foods, [made] Using the same ingredients and the same recipe, how can the fermentation have different flavors and results? That’s a big question and we don’t have all the answers at this point.” Marko, who was not involved in the new study, said.
To study the fermentation process, Kim and his doctoral adviser, Georgia Tech fluid mechanics scientist David Hu, used a combination of experimentation and mathematical modeling.they make kimchi OMG Allows more bacterial growth than in a sealed glass jar. More importantly, researchers have uncovered the cause. OMG The perfect vessel for this process.
“I thought it would be an interesting approach to try to figure out how different methods of making fermented foods affect the food that is produced,” Marco says.
Differences between containers relate to their permeability, or how quickly liquids and gases can pass through them. Goldilocks conditions are necessary to produce good kimchi, says Kim. Fermentation vessels should be semi-permeable, not overly permeable or impermeable.
Permeability is important because it affects the subtle dance of carbon dioxide and lactic acid bacteria. These microbes naturally migrate from the soil to the vegetables that grow there, including cabbage and other ingredients that form the base of kimchi. During the salty fermentation process, lactic acid and other types of bacteria multiply and release carbon dioxide, which begins to build up in the container. The researchers’ results demonstrate that lactobacillus “grows at moderate carbon dioxide levels,” Kim said. But excess carbon dioxide has to go somewhere. Otherwise, it will eventually grow to a high concentration that will hinder the growth of the most important bacteria. Conversely, if the vessel is too permeable, carbon dioxide will be expelled quickly and bacterial growth will be reduced.
After Kim purchases an unglazed OMG From his hometown on Jeju Island, South Korea, he and Hu measured the carbon dioxide levels of salted cabbage as it fermented in both vessels. OMG and tightly sealed glass bottles. For each bottle he performed three tests and sterilized the container in an autoclave before each test. For accurate measurements, researchers covered: OMG It has a custom made lid that can accommodate pressure, carbon dioxide and oxygen sensors. A thin plastic film was then used to seal the remaining gap between the sensor and the lid. In their study, Kim and Hu noted that the glass bottles leaked a little, albeit less than the leak. OMG.
Two days per trial, plenty of cabbage OMG I put the glass jar in the oven set at 25 degrees Celsius. “I set it higher than usual [temperature] It’s to speed up the fermentation process,” says Kim. Although kimchi can be fermented at much lower temperatures, such as 5 degrees Celsius, Kim and Hu noted that the only change caused by higher temperatures was “the speed of the process.”
The researchers also used electron microscopy and computed tomography scans to investigate its porous structure. OMG It then calculates the “gas permeation coefficient”, or how easily a gas can pass through it. They found this value to be more than double that of glass bottles.because OMG Carbon dioxide was able to escape faster than glass, and lactic acid bacteria grew. The carbon dioxide didn’t release as quickly in the glass bottle, so the gas slowed down the growth of the bacteria. “Its porous structure OMG Mimics loose soil inhabited by lactic acid bacteria. [are] It was found naturally,” the researchers wrote in their paper. This ensures that the fermented food in the container becomes saturated with microorganisms.
The researchers also OMGExperiments from Korean culture examined the penetrability of They filled the container halfway with salt water and showed that within 8 hours a salt deposit began to cover its outer surface. “In Korean culture, we call it ‘salt flower,'” says Kim. This phenomenon is usually observed when Korean chefs ferment soy sauce (or soy sauce). odd number) of OMG. When this salty flower appears outside the house, OMG, They are thought to mean that that particular container is permeable enough to make a top-notch sauce.
“Even in ancient cultures, [kimchi makers used] We adjust the gas levels to optimize the fermentation process,” says Kim. Large-scale kimchi producers combine glass, plastic, or metal jars with gas conditioning systems, but Kim and Hu’s research OMG We can achieve the same goals ourselves.
Perhaps as a result of that ability, traditional vessels are still in demand today and craftsmen continue to make them. OMG It is something kimchi lovers can use to achieve high quality fermentation.
