If you’ve ever eaten yoghurt, crunched into a tangy pickle, or curled up with a cosy hot chocolate, you’ve already met fermentation. You might even have taken part in a form of it at home, like when milk in the fridge went a bit sour.
Eating fermented foods connects you to a long line of people that came before you. Because your ancestors have been fermenting food for thousands of years.1 Fermentation unlocks extra nutrients, boosts gut health, improves flavour, and keeps food safer for longer.2 This helped early humans survive. Admittedly, most of us have fridges and freezers to extend the life of our food today, but jars of homemade sauerkraut and bottles of fizzy kombucha still have a special place in our kitchens.
So, what’s actually happening inside that jar of pickles?
What exactly is fermentation?
Fermentation is nature’s way of letting friendly microbes (bacteria, yeasts, and sometimes moulds) do some of the hard work in the kitchen for us. These helpful microbes break down sugars and starches in food, producing acids, alcohol, or gases along the way.3 The acids and alcohols help preserve food, keeping it safe and tasty for longer, while the gases make bread rise or give fizzy drinks their bubbles.
The fermentation process is usually anaerobic, meaning it happens without oxygen.3 That’s why people pack food tightly into jars or even bury it underground — to keep air out and let the right microbes get to work.
Fermentation isn’t the same as food going off. When food spoils, it’s because harmful microbes have taken over, making it unsafe or unpleasant to eat. Traditional fermentation, on the other hand, is a process where helpful microbes transform food. They preserve it, create new flavours, and often make food more nutritious.
On a microscopic level, tiny microbes are doing invisible work inside our food. We can’t see the bacteria or yeasts themselves, but we notice the results: bubbles forming in sourdough or kombucha, tangy flavours developing in sauerkraut, and creamy textures in yoghurt. These microbes help preserve food by creating an environment where harmful bacteria can’t grow as well, and they boost nutrition by making vitamins and minerals easier to absorb.4 5 Many of them are also probiotics.5
What are probiotics?
Probiotics are the “good” or “friendly” bacteria found in many fermented foods. They help keep your gut healthy by supporting digestion, fighting off harmful bacteria, and strengthening your immune system. A balanced gut microbiome can also improve mood and overall wellbeing: find out more here.
Fermentation: nature’s food preservation
Fermentation doesn’t just make food taste tangy and exciting. It also helps keep it safe to eat. The natural acids, alcohols, and other byproducts created during fermentation slow down the growth of harmful bacteria. This means foods like sauerkraut, pickles, and kimchi can last weeks or even months when stored properly.
This preservation power is one reason so many different foods and drinks around the world are fermented, including:
- Pickled foods, like vegetables preserved in salt water or vinegar.
- Sauerkraut, the tangy shredded cabbage of Central and Eastern Europe.
- Yoghurt, fermented from milk and full of friendly bacteria.
- Wine and beer, where alcohol is both a preservative and something people drink for enjoyment.
- Chocolate, which is made by fermenting cacao beans to develop flavour before roasting.6
These are just a few examples. Fermentation is found in cultures all around the world, and there are countless recipes and specialities that use good bacteria to create unique flavours and preserve food.
Originally, it was about survival: keeping milk, grains, vegetables, meat, and fish edible for months after harvest. What started as a practical survival strategy gradually became a rich cultural tradition, with recipes and rituals passed down over centuries. So how does this look in kitchens around the world?
Fermented favourites: global traditions, local flavours
Fermentation truly spans the globe. While some foods may sound unusual to outsiders — like eggs or whole birds buried for months underground — in their cultures, they are prized delicacies. Here are some more examples of global fermented foods:
- In ancient China, soybeans were fermented to create “jan,” an early version of soy sauce that continues to flavour our meals.7 (Yes, soy sauce is fermented!)
- In Indonesia, tempeh, also made from fermented soybeans, became a protein-rich staple that is still enjoyed around the world.8
- In parts of Africa, fermented porridges and drinks have long been used to help babies stay healthy as they start eating solid foods. The natural acidity makes the foods less likely to go off, keeping them safe and nutritious.9 10
Europe has a rich history of fermented foods, too. Sauerkraut, the tangy shredded cabbage of Central and Eastern Europe, kvass, a bread-based drink popular in Eastern Europe and Russia, and countless strong cheeses all show how communities preserved harvests and developed flavours we still love.
But what do all these specialities have in common? They might use different ingredients and be shared around tables that speak different languages, yet the common thread is the same invisible magic — the friendly microbes that make fermentation possible.
Meet the microbes behind the magic
Lactic acid bacteria are tiny microbes that help make many fermented foods. They grow best without air and produce lactic acid. This acid makes foods taste sour and also helps stop harmful bacteria from growing.11 That’s what happens in yoghurt, sauerkraut, kimchi, and sourdough.
Yeasts, on the other hand, turn sugars into alcohol and carbon dioxide.12 That’s how we get puffed up bread, bubbly water kefir, and alcohol in our wine. And then there are moulds, which create blue veins in cheese or break down soybeans for miso.
These tiny, invisible helpers transform food in ways that other processing methods can’t. Unlike chopping, cooking, freezing, or drying, fermentation actually changes the balance of microbes in food, adds new flavours, and often increases nutrients. Humans figured out this microbial processing long before modern science could explain why it was so good for us.
Many supermarket ferments — like sauerkraut, kimchi, or kombucha — are pasteurised, meaning they are heated to make them shelf-stable. This process kills the live microbes, which lowers the probiotic benefits, but keeps the products stay safe for a long time.13 Homemade ferments are tangy, fizzy, and full of beneficial probiotics, but they usually need to be eaten sooner.
Why fermented foods are good for you and your gut
Fermentation can make food more nutritious by breaking down some of the sugars, starches, and proteins, which helps our bodies absorb vitamins and minerals more easily. For example, fermented vegetables and dairy often contain higher levels of B vitamins, vitamin K2, and antioxidants than unfermented versions of the same food.14 15
Fermented foods also bring us beneficial bacteria, or probiotics, which help maintain a healthy balance of microbes in the gut. But, watch out. These friendly bacteria won't stick around for long if we don’t give them anything to eat. Once beneficial microbes are in our digestive system, we can help them thrive by eating a varied, fibre-rich diet. Fruits, vegetables, whole grains, legumes, and nuts all feed our gut bacteria, keeping them active and healthy.16
Fermentation today: why the comeback?
Fermentation has been around for a long time, but market insights tell us that it is growing in popularity with modern foodies.17 So, why is this?
Health: fermented foods are linked to better digestion, stronger immunity, and even improved mental health through the gut–brain connection.16 As awareness of these benefits grows, so does people’s interest in eating (and making) fermented foods.
Tradition: many people are drawn to foods made using time-honoured techniques and fewer artificial ingredients. Fermentation fits perfectly into this movement, blending craft, culture, and nourishment.
Sustainability: fermentation helps reduce food waste, especially for home growers. A surplus of cabbages or cucumbers can be transformed into jars of kraut or pickles instead of ending up in the compost.
Flavour: the tang, fizz, and depth of fermented foods are almost impossible to create in other ways, adding excitement and richness to everyday meals.
Creativity: fermenting at home is hands-on and a lot of fun. People are rediscovering traditional recipes or inventing new ones, supported by a wealth of free tutorials and online communities that make experimentation easy and accessible.
Find out more about fermented bread, and what it actually does for you
The future of fermentation
Modern science is now pushing fermentation into new territory. Precision fermentation uses microbes in carefully controlled environments to produce specific proteins. This technology has already given us life-saving medicines like insulin and vegetarian alternatives like mycoprotein, and it may help create sustainable foods in the future.18
Try it yourself: easy ways to start fermenting
Feeling inspired to give fermenting a go in your kitchen?
It’s surprisingly easy to ferment your own food, and you don’t need loads of fancy gear. For thousands of years, people did it without scales, thermometers, or sterile labs. Today, a clean jar, salt, and vegetables are often enough.
Sauerkraut survival guide
Homemade sauerkraut will stay good for 3–6 months in the fridge. Here’s how to keep it safe and tasty:
- Use a very clean jar.
- Always scoop it out with a clean spoon.
- Keep it in the fridge once it’s fermented to your liking.
- Make sure the cabbage stays covered with its brine (salty water) to prevent mold.
Your sauerkraut will keep slowly fermenting in the fridge, getting tangier over time. If it ever smells bad or looks off, it’s time to say goodbye.
Where to learn more? Local libraries, online videos, and community workshops are full of guidance. Just remember: recipes are guides, not rules. Clean jars and good habits keep things safe, but there’s plenty of room for curiosity and personal taste.
Fermentation for life
Fermentation is much more than a fashionable cooking method. It’s a universal human tradition that:
- Keeps food safe for longer.
- Enhances flavour and nutrition.
- Connects us to ancestors, communities, and cultures.
- Offers tools for health and sustainability.
Every spoonful of yoghurt, every bite of sauerkraut, every sip of kvass or kombucha can support our health and carry cultural traditions forward to the future.
