How Does Fermentation Work? A Primer

Fermentation, fermenting, it’s becoming super popular, but what does it mean? This is a question I get asked all the time when I tell people about my fermentation projects, from kombucha to kimchi and everything in between. So, how does fermentation work and why is fermentation important to the modern homesteader?  Is it something you should be honing your skills in? My answer is a solid YES, but then I’m biased. I ferment all sorts of things, milk into kefir, cabbage into sauerkraut in my fermentation crock pot, you name it, I’ll ferment it!

Before we go on, take moment to think about the foods you eat and the beverages you drink. How much of it is fermented in some way? Quite a lot actually. Beer, wine, cheese, yogurt, bread, there are many modern foods that undergo fermentation in the production process. So we all eat foods that have been fermented, even if the healthy yeasts and bacteria that played a vital role in the process have been killed off when the product reaches our lips.

When I talk about fermentation, I’m really interested in the lacto-fermentation process that is used in the production of many traditional foods such as kimchi and sauerkraut, Curtido and dill pickles. It’s also happening in kombucha and kefir milk, the milk-based fermented drink that has been around for 2000 years or more.

These raw, live products are extremely healthful and are now making a resurgence into our consciousness. Fermentation has been used since Neolithic times with evidence going back to 7000 BC in China, then spreading around the world to India, Georgia, Egypt, Mexico, and Sudan. There is also a religious significance in Christianity and Judaism for fermented food and drink.

This simple process of how to make fermented foods requires salt, water and vegetables or fruit, it really is that easy. All you really need to get started fermenting vegetables is a large jar and some very basic kitchen implements.
How Does Fermentation Work

The Lacto-Fermentation Process – How It Works

Also known as anaerobic fermentation (although fermentation does not always need to occur in an anaerobic environment), lacto-fermentation works with very little involvement from us humans, which is a good thing! Ancient people probably discovered it purely by accident, learned to duplicate and refine what they saw, and created a system of preserving food for the leaner times when fruit and vegetables were scarce.

When we take a cabbage, carrot, berries or some other vegetable, even though we may wash it, the leaves and outer surfaces are abundant in naturally occurring yeasts and bacteria. When we shred these vegetables and cover them with brine, or use our hands to cause the salted cabbage to give up its water, any harmful bacteria on the food is killed off. Bad bacteria don’t handle salt well, good bacteria are very tolerant….luckily for us.

So, we take our vegetables, we add salt or a saltwater brine solution and submerge the veggies under the surface of the liquid. The bad guys are killed, the good guys are left to do their thing in the second stage of the lacto-fermentation process.

The Chemistry Of How Fermentation Works

How Does Fermentation Work Chemistry
It’s Really Not This Complicated!

Let’s discuss lactobacillus. Ever heard of them? These are the good bacteria I was discussing a few moments ago, the ones that are super tough and tolerant to salt. This genus of bacteria has many different species, the thing they have in common is that they eat sugar, the sugar in the plants we are fermenting, the sugar in the sweet tea we are using to make kombucha. They’re lactose (sugar) eaters. They hungrily devour the natural sugars and turn them into lactic acid. You may have heard of lactic acid when people talk about the burn in your muscles when doing hard exercise.

Well, the lactic acid produced by the lactobacillus bacteria act as a natural preservative that preserves the food and also the nutrients in it. This is why fermented foods that have been stored for long periods of time are still rich in nutrition.

As well as tasting great, lasting a long time in storage, and having great nutritional value, consuming the lactobacillus bacteria (which may have many species in a single mouthful), these incredibly healthy bacteria will contribute to a healthier gut and digestive system. The gut is gaining much significance as a major contributor to health or disease, depending on how healthy it is. Many people eat a poor diet that leads to inflammation, they take antibiotics which kill the good bacteria in the gut.

It’s becoming clear from research that the number, and diversity of healthful bacteria is vitally important to your overall health. And eating raw, unpasteurized fermented food really works to increase those numbers.

Stages In The Lacto-Fermentation Process

So, the process of lacto-fermentation involves submerging vegetables in a brine solution. This can be salt and filtered water, or, as I often do, just salting the vegetables at around 1 tablespoon of salt per head of cabbage for example, then massaging the cabbage which allows the water in the vegetable to be released. It’s often a reasonable amount of liquid. The cabbage, in this case, wilts as the liquid is released. When you pack the cabbage into your jars or fermenting crock, the excess liquid can be poured over the top to cover. If you are a little short on liquid, then a little brine can work great to top things up.

Fermenting can actually take place without salt added, but as discussed, salt works great to eradicate those pesky bad bacteria that may be lurking. Let’s look at the next steps, and find out when does fermenting occur.

The salt-brine fermentation is a two-stage process.

Stage 1  – Submerge the vegetables in a brine solution (and/or use the expelled liquid from the vegetables if you are not using added water). Make sure the vegetables remain below the surface of the liquid, occasionally you may need to top this up as the days go by, just keep an eye on it. The bad guys are killed off and the awesome lactobacillus fellas remain and begin the second stage of the fermentation process.

Stage 2 – The lactobacillus organisms start chomping away on those lactose and other sugars and produce lactic acid as the waste product.

Lactic acid is, as you might guess, and acid, so when this is produced the environment in the jar or crock becomes acidic. This preserves the vegetables and gives the tangy flavor that is so distinct with lacto-fermented foods.

How Fermentation Works (video)

This 3-minute video on fermentation biology will help explain how fermentation works

How Is Fermentation Different To Canning?

A lot of people get muddled up between the concepts of fermentation and canning. Both are used to preserve food, but canning can be used to store food for much longer. Fermented foods are not designed to be preserved for years and years, although it appears that the Koreans love their kimchi when it’s reached 3+ years old! So although fermenting and jarring vegetables extends their shelf life way beyond just leaving them in the vegetable basket or in the fridge, the product ‘can’ spoil. That said, if you open a jar of fermented vegetables and see a little mold forming, it’s usually ok to scrape this off. If the vegetables underneath look fine, it smells and tastes good, then one can often still eat them.

Canning as a method of preserving is very different. The idea is to sterilize the foods, which is why food is often put into cans or jars hot, with the jars also being heated. When the foods and jars cool, it creates a vacuum in the jar, keeping the environment free from air, with all bacteria killed. Canning is great, I use it for storing the glut of cherry tomatoes I always have, but it does not provide the healthful bacteria that the fermentation process does. Both are good, just different.

Best Vegetables For Lacto-Fermentation

Vegetables For Fermenting
Most Vegetables Can Be Fermented – Be Adventurous

One can certainly ferment any vegetable, but some lend themselves more to successful fermentation than others. Ideally, a vegetable with a decent structure, that is not going to just fall apart in the brine solution is best. Imagine something as delicate as cucumber or tomatoes. They certainly can be fermented, in fact, I have a great recipe for making tomato sauce and fermenting it after it is made, but when we are talking about the best vegetables for fermentation, think:

  • Cabbage
  • Carrots
  • Green Beans
  • Chard
  • Sugar Snap Peas
  • Daikon Radish
  • Radish
  • Garlic
  • Cauliflower
  • Broccoli
  • Turnips
  • Capsicum
  • Chilli Peppers
  • Kale

Do you get the gist? Veggies with a structure that can hold up to the process. Of course, mixing these creates some inspired results, add in some spices or herbs and you really are going to improve your health, add some diversity to your diet, and use up that glut of produce that we all get on our small homesteads.

Hope this has been useful, please leave a comment if I can help you further.

Happy Fermenting!

Further Reading:

How To

How To Make Kefir Milk At Home

How To Ferment Beets

How To Make Sauerkraut In A Crock Pot Or Mason Jar

Recommended Fermenting Accessories

Here are a few cool things that you might want to consider if you decide to start fermenting. I love my cabbage pounder and also have a shredder similar to the one below. I've used a knife for a long time, but the shredder speeds the process.

Himalayan salt is the best in my view, check out my article on the best type of salt for fermenting if you'd like to learn more.

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