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  • Alex Cloherty

Eat your cabbage.

Have you ever tried sauerkraut? Or maybe the Korean variation, kimchi? Then you've tried Lactobacillus.

Fermented foods like these cabbage-based delicacies are made by harnessing the power of the Lactobacillus bacteria! Lactobacilli are all over the place - not only on and in humans and other animals, in other fermented foods like yogurt and kombucha and sourdough, but also all over vegetables. I recently made sauerkraut for the first time, and was impressed to learn that the Lactobacilli species that naturally live on the surface of vegetables are all that's needed to kick-start your fermentation culture!

Preparing my sauerkraut, i.e. my bacteria baby

So how does this process work exactly, from a microbiological point of view?

Fermenting vegetables works in the same way as fermenting milk into yogurt, or tea into kombucha does. At the beginning of the process, there are a lot of different bacteria - not only Lactobacilli - on and in the cabbage (or whatever else you might have selected). Some of these bacteria are considered to be "good", or "probiotic", while other bacteria could be neutral or harmful, depending on how and where the cabbage was grown. For example, if feces was used as a fertilizer, there could still be some poop bacteria hanging around. Somehow, centuries ago, people all over the world managed to discover that fermenting vegetables in salt eliminated those bad bacteria, without even realizing that bacteria existed! Pretty amazing, right?

Adding a bit of salt into the water or vegetable juice (for sauerkraut, you simply add salt and smush the cabbage until you have enough cabbage juice to act as brine) effectively kills off most of the non-Lactobacillus bacteria while letting the Lactobacillus flourish. For example, Enterococcus faecalis and Lactococcus lactis are often found at the early stages of sauerkraut fermentation, but soon die off.

There are a few different types of Lactobacillus that take over after the death of the other bacteria, including Lactobacillus plantarum, Lactobacillus pentosus, Lactobacillus brevis, Lactobacillus fermentum, and Lactobacillus kimchi (that's right, there's even a species named after kimchi). This multi-species ecosystem of Lactobacilli work together to eat up the sugar present in the cabbage and turn it into lactic acid. This lactic acid is beneficial to us humans in a similar way to the salt at the beginning of the fermentation process: it inhibits the growth of microbes that could do us harm, including not only "bad" bacteria, but also fungi for example. And, as an added bonus, it gives fermented veggies that tangy taste.

It is these same Lactobacilli, or lactic acid bacteria, that are considered to be the powerful "probiotics" in yogurt, kefir, and all those other fermented "superfoods" you've been hearing about. Fermentation-associated lactic acid bacteria have been claimed to have wide-reaching positive health effects, from cholesterol reduction, to promoting immune system functioning, to improving skin health. However, as more scientists become interested in this topic, there is also research coming out and finding little effect of probiotics, at least not in healthy adult populations. The effectiveness of probiotics is a big can of worms that we'll get into in a different Microbial Mondays post. For now, at the very least we know that eating fermented vegetables is 1) definitely not harmful, 2) a great way to preserve food that you might otherwise waste, and 3) helps you get to the right number of veggie servings per day!

So, until next week, eat your kimchi!


PS. If you want to know more about fermenting your own food, check out these websites that I found!





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