I’m sure you’ve eaten your share of sauerkraut (kimchi, pickles, or other fermented foods), but have you ever wondered how the fermentation process works? If your backyard garden is giving you bumper crops of coleslaw perhaps it’s time to consider employing anaerobic bacteria to help you turn some of that cabbage into kraut.
Cabbage is covered in naturally occurring bacteria such as Leuconostoc, Lactobacillus, and Pediococcus. When these bacteria are exposed to the right conditions they start the process of lacto-fermentation. Sauerkraut can be created without starters, cultures, or other additions. This is why the process is called wild fermentation. It doesn’t require you to have a specific set of microorganisms on hand.
Sauerkraut preparation begins by thinly slicing cabbage and sprinkling it evenly with sea salt. The salt causes the cellular walls of the cabbage to lose water, which decreases the volume of the cabbage. It also acts as a preservative and an inhibitor to unwanted bacteria. Along with water, the salt helps to leech nutrients and sugars from the cabbage. These create a perfect growth medium for the bacteria needed to ferment the cabbage.
The key to creating sauerkraut is to keep the environment free of oxygen. The bacteria that act to ferment the cabbage are anaerobic, which means they don’t use oxygen. However, lots of other bacteria, fungi, and molds do use oxygen so keeping the environment free of oxygen is the primary concern. This is done by submerging the cabbage in the liquid leeched off the cabbage and packing it tightly in a container. The entirety of the cabbage should be covered in brine for fermentation to work correctly. As the fermentation process continues carbon dioxide gas is released, so people often use a smaller container set into a larger one to keep pressure on the cabbage (and to keep the cabbage under the brine) while the process is occurring.
Wild fermentation is like a crazy war game. The first bacteria to hold dominance are cloriforms that increase the PH as they grow. Pretty soon the PH is so high that the cloriforms die off leaving room for the next invaders, the naturally occurring Lactobacillus. These bacteria thrive in highly acidic environments without oxygen. Eventually, they consume enough of the sugars and nutrients in the brine (while giving off lots of CO2 in the meantime) to lower the PH again. With the cloriforms dead and the Lactobacillus on the way out Leuconostoc (and sometimes Pediococcus ) finish the fermentation process by gobbling up the remaining sugars. These bacteria aren’t harmful to humans and do a great job of preserving the cabbage for future meals.
The process can take a few days or a few weeks depending on external conditions such as temperature and exposure to oxygen. When sauerkraut is properly cured the environment is so acidic that botulism and other harmful bacteria can’t survive so it doesn’t require pasteurization to be safe for human consumption.