Kimchi & Kombucha | How It’s Made

Fermented foods like kombucha and kimchi are becoming more and more popular – but what does fermentation actually involve? Here’s everything you need to know about this ancient technique.

What is fermentation?

Fermentation is a process that many foods go through before they reach our shelves and refrigerators, including bread, cheese, wine, yoghurt, and even coffee. It happens when microbes or enzymes start breaking down carbohydrates, like sugars.¹

In nature, fermentation happens to fruits and vegetables that have been left to rot. But when we control the process of fermentation, rather than being an unwelcome deterioration, it actually brings benefits. Fermentation can increase the shelf life of food, decrease the need for refrigeration, and – last but not least – make foods tastier (depending on your taste).

People around the world have been purposely fermenting foods for thousands of years – in fact, it might be the oldest form of food preservation.

The Science Behind Fermentation

From Korean kimchi to German sauerkraut, different cultures have their own specialised recipes for fermented foods. But each time, the basic principle is the same: allowing certain helpful microorganisms to break down carbohydrates in the food and create acids or alcohol, making an environment that’s hostile to harmful microorganisms.

Bacteria, yeasts, and moulds can all be involved in fermentation.¹ While it might seem counterintuitive to encourage bacteria to grow on food, there’s a huge diversity of microbes out there, and some of them count as “good” bacteria that help rather than hurt us.

In fruits and vegetables, the most important bacteria involved in the fermentation process is lactobacillaceae, which breaks down carbohydrates to form lactic acid. Sauerkraut, kimchi, and some other pickles get their sour, tangy taste from this acid. But it doesn’t just affect taste: the acidic environment is what preserves the food and prevents harmful bacteria from growing.²

Fermentation Processes of Alcohol & Vinegar

Another common bacteria used in fermentation is acetobacter, which produces acetic acid. To ferment fruits into vinegar, both yeast and acetobacter work together: the yeast turns sugar into alcohol, and the acetobacter turns the alcohol into acetic acid, which is what gives vinegar its distinctive taste.

Wine and beer are made by fermenting grapes and barley, respectively, in a version of this process that minimises the amount of vinegar produced. A yeast commonly used in the production of wine and beer is called Saccharomyces cerevisiae, but a variety of different species, including wild strains, play important roles in creating the huge variety of alcoholic drinks available to buy.³

Kombucha, the slightly sour, fizzy drink that’s become popular in recent years, is also made using both yeast and bacteria, which are added to tea that’s been sweetened with sugar to feed the bacteria.

Gut Health & Fermented Foods

Humans didn’t invent fermentation: it also happens inside your gastrointestinal tract, aka your gut. The same kinds of helpful bacteria that we use to ferment foods in the outside world, alongside many other microorganisms, are involved in digesting the food you eat.

This has led to suggestions that eating fermented foods containing these helpful microbes could enhance your digestive system’s microbiome – the population of microorganisms that live in your gut – and help it work as it should.⁴

But a lack of evidence and the huge variety of fermented foods available means that the jury is still out on how beneficial drinks like kombucha really are for people who already have a healthy gut.⁵

However, there are some circumstances where fermentation can make a difference. People who are lactose intolerant, for example, might be able to digest cheese and yoghurt more easily than they can digest milk because the lactose found in milk has been broken down into simpler sugars.

Fermentation at home

If you’ve ever left a bottle of wine open for several days and then had to throw it away because it tastes too vinegary, you’ve already (unwittingly!) begun experimenting with home fermentation because the alcohol in your wine has broken down into acetic acid.

Fermenting your vegetables is not much harder. Making sauerkraut, for example, involves thinly slicing a cabbage and mixing it with salt until it starts to break down and form its own brine, adding spices to flavour and then leaving it for several weeks to ferment and develop.⁵

If you do try fermenting at home, make sure the jars you use are sterilised – you can do this by washing them with soap and water and putting them in the oven for 15 minutes – to keep harmful bacteria at bay.²