Kimchi, a Korean side dish composed of seasoned, fermented vegetables, has become popular in recent years, especially among health-conscious consumers. The staple Korean accompaniment was the focus of a recent study led by Michelle Zabat ’18 and Will Sano ’16 and completed in the lab of Peter Belenky, assistant professor of molecular microbiology and immunology. The study explored the impact that different production methods have on bacterial communities withinthe fermented foods that people consume.
As more and more people look to buy kimchi and other fermented products such as sauerkraut, companies have changed their production methods to increase efficiency. The researchers studied the changes in fermentation processes that have come with this shift in production processes. Consumers have particularly been attracted to kimchi because it is a probiotic, meaning it promotes the proliferation of healthy bacteria within the body. “Recently, with the whole rise of probiotics as a concept, fermented foods are becoming more popular, especially in health conscious circles in the United States,” Zabat said.
“The science behind (probiotics) is not as rigorous as it could be,” Belenky said. “We don’t yet know which probiotics are important, but nonetheless a lot of the reasons why people purchase things like kimchi, kombucha, or yogurt … is because they believe it has a benefit for them, from the probiotic perspective,” he added. The study took a closer look into these foods and assessed the bacterial population that people ingest when they eat these products. Studies like this one help people gauge whether or not foods actually do contain probiotic bacteria, he said.
To accommodate demand, production companies have started to break from traditional fermentation methods, Zabat said. For example, some have started to replace the typically used fermented seafood with miso paste, making the product vegan.
“Both of those ingredients contain their own communities of lactic acid bacteria that will ferment the material,” Belenky explained. The project aimed to establish whether or not vegan production methods produced a differing final bacterial composition, and concluded that it did not.“If you want to make vegan kimchi, it’s going to have the same final bacterial properties as the traditional kimchi,” he added. “The selective pressure of the fermentation environment is so strong that it doesn’t really matter what your input is. … You will establish a (bacterial) community that is the same, no matter what,” he explained.
In order to evaluate the bacterial compositions of the various kimchi models, the researchers analyzed samples taken from the ingredients that compose kimchi, the fermentation facility and the final product. Then researchers sequenced the DNA of these bacteria, which allowed them to identify which bacterial species were present, she said. Inspired by Belenky’s personal passion for fermentation and Zabat’s interest in food science, the project started as a “side venture” in the lab, which focuses primarily on microbiomes in the human body and environment, Sano said.
“I almost view kimchi as a small, microcosm of (the lab’s greater focus). It is also a microbial community that responds to a stressful stimuli,” Belenky said, explaining that the salty conditions in which kimchi is produced are analogous to the stressors that are studied with regard to the microbiome in humans, for example.
The lab’s capabilities were well suited to the researchers’ interest in food science, given that the study called for many of the same methods employed by other microbiology research. “What’s exciting about the technology that exists for profiling bacterial communities is, you don’t need to sequence the entire bacterial genome in order to figure out what they are,” Sano said. A single, short gene, 16S, codes part of the ribosome and can be sequenced to determine the species of a bacterium.
The project served as an opportunity for Zabat and Sano to gain experience in a low-stakes context, Sano said, adding that it allowed them to gain expertise in the necessary methods without involving high-risk, high-cost human tissues. Both Zabat and Sano plan on building upon this experience in their future endeavors.