Kimchi is a simple Korean pickle, a fermented mash-up of vegetables like napa cabbage and scallions. It’s easy to make. And it’s everywhere: from modest ramen houses to the trendiest of tapas bars. It’s crossing cultural barriers on menus and filling home refrigerators, from the dorm room to your suburban mom’s well-stocked kitchen. Chefs are slapping it on burgers, layering it into grilled “kimcheese” sandwiches, and even sneaking it into your Bloody Mary. But how can something as basic as cabbage, salt, and spices be so buzzworthy? It’s simple: science.
Kimchi relies on fermentation, or the digestion of sugars into acid, gases, or alcohol (don’t worry, your kimchi won’t be boozy). It’s the fermentation process that gives kimchi its trademark effervescence, tang, and delicious funk, harnessing the natural interactions between bacteria and their environment.
Fermentation is a delicate balance of biology and art—the two things that I’m most passionate about. I didn’t always think I’d become a chef. I studied microbiology, ecology, and evolutionary studies in college. My favorite classes were focused on the interaction between species in a given niche environment. I loved learning how different animals face natural challenges, adapt to best survive, and consequently influence each other. While I enjoyed what I was studying, I loved my night job as a line cook even more. I had planned to go to veterinary school after college. But, in the end, my love for food was stronger than my love for puppies. I left the world of Petri dishes behind in exchange for one of sauté pans. When I started developing a recipe for kimchi for the America’s Test Kitchen book Foolproof Preserving, which came out in April 2016, I had no idea those two worlds were about to collide.
To develop my kimchi recipe, I started by salting the cabbage, a traditional step that draws out excess water. (Nobody likes a soggy pickle.) I then added a potent paste of garlic, ginger, Korean chili powder (gochugaru), sugar, fish sauce, and soy sauce to bring out complexity, heat, and a peppery freshness. I kept my vegetable selection simple: napa cabbage, scallions, and carrots. From this point on, the kimchi just needed to ferment, which would happen naturally when left alone in a jar in the kitchen cabinet. So, basically, I was done! Or so I thought.
But my first attempt was . . . gross. After just three days in a kitchen cabinet, the kimchi pickle was bubbling, overly sharp, and mushy. One taster described it as having too much “zing!” and not enough depth, while another described it as having an overpowering cheesy and dirty flavor. (Nobody wants a dirty pickle.)
What was going on? I started to do some research and learned that, traditionally, kimchi is often fermented in cool pits in the ground—a very different setup from my warm kitchen cabinet. Because kimchi relies on an important balance of salt and a type of bacteria called lactobacilli for preservation, I needed to create the ideal home for these bacteria to thrive. These guys are facultative anaerobes, meaning they can survive both in the presence and absence of oxygen. Either way, they create lactic acid as a by-product of their digestion, which creates an acidic environment, lowering the pH (the measurement of how acidic, neutral, or alkaline something is) and preserving (or pickling) the cabbage. The lactobacilli also make carbon dioxide (which results in the bubbly zing) and create flavorful compounds.
Clearly, lactobacilli’s work is important, and this is why salt is so key. Salt prohibits the growth of unwanted bacteria, giving our beneficial buddies, who are largely salt tolerant, enough time to dominate and pickle the vegetables. But adjusting the salt in my kimchi mixture wasn’t enough to get the texture and flavor I wanted. I decided to tackle the other variable at hand: temperature.