If you've ever enjoyed a glass of kombucha, a slice of sourdough bread, or a spoonful of yogurt, you've already experienced fermentation firsthand. But what is fermentation, exactly? What's actually happening inside that jar, loaf, or bottle, and why does it matter?
Fermentation is a natural process and one that humans have been harnessing for over 10,000 years. It preserves and transforms and is responsible for some of the most complex flavours we know. It puts the fizz in your fermented drink, the sour in your sourdough, and the tang in your kimchi. Once you understand what fermentation is and how it works, you'll start seeing it everywhere.
In this post, we’re lifting the lid and seeing what’s really going on when you ferment your food and drink.
What Is Fermentation? The Simple Definition
Let's start with the basics. Fermentation is a natural metabolic process in which microorganisms, primarily bacteria, yeast, or fungi, convert sugars into other compounds like organic acids, alcohol, or carbon dioxide in order to survive.
This process also transforms the flavour, texture, shelf life, and nutritional content of food and drink, leaving us with something even better than we started with.
Good™ to know: The word itself comes from the Latin fervere, meaning "to boil," which describes the bubbling you as a result of fermentation.
The Main Types of Fermentation
Fermentation takes many forms across food and drink, but most of what you'll encounter falls into two primary categories.
Lactic Acid Fermentation
Lactic acid fermentation is the common type of fermentation in food production, and chances are, you’re already eating it. In this type of fermentation, lactic acid bacteria consume sugars and produce lactic acid as a byproduct. The result is that familiar sour, tangy flavour. The new acidic environment also inhibits the growth of harmful bacteria, naturally preserving the food.
Foods and drinks made through lactic acid fermentation: yogurt, kefir, kimchi, sauerkraut, naturally fermented pickles, sourdough bread, certain fermented sodas.
Alcoholic Fermentation
In alcoholic fermentation, yeast (and sometimes bacteria) convert sugars into ethanol and carbon dioxide. The amount of alcohol in the final product depends on how much sugar was present and how long fermentation runs. The CO₂ creates natural carbonation in drinks like kombucha.
Foods and drinks made through alcoholic fermentation: beer, wine, cider, kombucha, water kefir.
Other Types of Fermentation
Beyond these two main categories, other fermentation processes include:
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Acetic acid fermentation — used in vinegar production, where ethanol is converted to acetic acid by specific bacteria.
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Propionic acid fermentation — responsible for the characteristic holes and flavour of Swiss cheese.
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Koji fermentation — a mould-based fermentation central to Japanese cuisine, used to produce miso, sake, and soy sauce.
Who Does the Fermenting? Meet the Microorganisms
The type of fermentation and the end result really depends on the type of microorganism doing the work. Sometimes it’s just one, and other times there are multiple microorganisms doing their thing at once.
Here are the some of the heroes of fermentation:
Bacteria
Lactic acid bacteria (LAB) are responsible for many of the fermented foods we know and love. They convert sugars into lactic acid, producing that characteristic sour, tangy flavour and creating a naturally acidic environment.
Good to know: Good Sodas™ use lactic acid bacteria fermentation, giving our sodas a fresh acidity and depth of flavour.
Yeast
Yeast are single-celled fungi responsible for fermentation in bread, beer, wine, and certain kombuchas. They convert sugars into carbon dioxide and ethanol (alcohol). The CO₂ is what makes bread dough rise and gives sparkling fermented drinks their natural fizz.
Mould
Mould is the microorganism in Koji fermentation and responsible for making miso, tempeh, sake, and many aged cheeses. This fungi breaks down proteins and fats into deeply savoury, complex, umami flavours.
SCOBY (Symbiotic Culture of Bacteria and Yeast)
Some ferments rely on a whole community of microorganisms working together. A SCOBY (Symbiotic Culture of Bacteria and Yeast) is the living starter used to ferment kombucha. It's a whole ecosystem of bacteria and yeast operating together converting sugars into ethanol and then ethanol into acetic acid.
Wild vs. Cultured Fermentation
Some fermentation starts wild. Some starts with a little help. Both are pretty magic.
Wild Fermentation
Wild fermentation relies entirely on naturally occurring microorganisms — those already present on the raw ingredients, on equipment, or simply in the air. No starter culture is added. The microorganisms that show up are determined by the environment, the season, and the ingredients themselves.
Traditional sourdough is the most well-known example: a mixture of flour and water, left out, will spontaneously begin to ferment as wild yeasts and bacteria from the grain and surrounding air colonise it. Wild fermentation tends to produce highly distinctive, terroir-driven flavours — but it's less predictable and harder to control.
Cultured Fermentation
Cultured fermentation introduces a specific, known population of microorganisms to initiate the process. This could be a spoonful of yogurt stirred into warm milk, a packet of dried yeast added to bread dough, or a SCOBY placed into sweetened tea. The starter culture gives you control over which microorganisms are active from the start.
This approach is far more consistent — you know what organisms are doing the fermenting, which means you can predict flavour, acidity, and fermentation time more reliably. Most commercial fermented foods and drinks use cultured fermentation for exactly this reason.
Good to know: At Good Sodas™ we use a lactic acid starter culture that's added to organic fruit juice (apple and white grape to be specific).
How Does Fermentation Work?
At its core, fermentation is about energy. Microorganisms need energy to survive and reproduce, and they get it by breaking down sugars. Here's what's actually going on.
Here's the basic process
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Sugars are present in food and drink, such as fruit, vegetables, grains, milk, or tea.
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Microorganisms are introduced. They can be naturally occurring on the ingredients, present naturally in the environment, or added as a starter culture.
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The microbes consume the sugars, producing acids, alcohols, gases, and other compounds as metabolic byproducts.
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The food or drink is transformed in flavour, texture, acidity, carbonation, and sometimes nutritional profile.
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The process slows or stops either because the sugars run out, the environment becomes too acidic for the microbes, or the ferment is moved to cold storage or heat-treated (pasteurised).
Curious about how we do it? Read about how we ferment our organic sodas.
What Does Fermentation Do to Food and Drink?
This is the real magic of fermentation. The process of fermentation is impressive in itself, but it’s the end result that really gets us excited.
Here’s what the process actually does to your food and drink.
It Transforms Flavour
It Transforms Flavour This one gets us every time. Fermentation builds acids, esters, and compounds that simply don't exist in the raw ingredients. The result is a complexity you can actually taste. That's the Good Sodas™ difference.
It Preserves
Long before fridges existed, fermentation was keeping food safe. The acidic environment created by lactic acid bacteria is inhospitable to harmful bacteria — salt, time, and the right microorganisms have been doing this work for thousands of years. Turns out the old way is still the good way.
It Enhances Nutritional Content
Fermentation does some of the digestion work for you. It breaks down hard-to-process sugars, phytic acid in grains, and certain proteins, making the naturally occurring nutrients more available to your body. It also produces B vitamins as a byproduct of microbial activity. The impact varies depending on the ferment, but the direction is consistently positive. What goes in isn't always what your body gets — and with fermentation, that's a good thing.
It Introduces Live Cultures
If you choose not to pasteurise your fermented goods, you get a probiotic food or drink that contains healthy microorganisms that can benefit your gut microbiome. Many store-bought fermented foods, Good Sodas™ included, are pasteurised for safety and stability, but more on that below.
Live Cultures vs. Pasteurised: What's the Difference?
Once fermentation is complete, a critical decision determines the character of the final product: is it kept alive, or is it heat-treated?
Pasteurisation involves heating the product to kill microbial activity. This stops fermentation, stabilises the product, and significantly extends shelf life. Many fermented foods that you can find on shelves in stores are pasteurised. The downside is that the live cultures are destroyed in the process.
Raw or unpasteurised fermented products keep their living microorganisms. The bacteria and yeast are still active in the bottle or jar. This means the product continues to change slightly over time, and it typically requires refrigeration. It also means the live cultures are present when you consume it.
Good™ to know: We choose to pasteurise our sodas so they are shelf stable and you can enjoy a consistently delicious soda no matter when you drink it.
Fermentation really is everywhere
Fermented food shows up in every culture on earth, and a lot of it is already on your plate without you knowing it.
Next time you come across a fermented food, see if you can recognise that signature fermented flavour — is it sour, tangy, or packed with umami?
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Category |
Examples |
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Dairy |
Yogurt, kefir, aged cheese, crème fraîche, sour cream |
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Vegetables |
Kimchi, sauerkraut, naturally fermented pickles, miso, curtido |
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Grains |
Sourdough, beer, sake, injera |
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Drinks |
Kombucha, water kefir, fermented soda, wine, cider, tepache |
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Legumes |
Tempeh, natto, soy sauce, doenjang |
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Meat & Fish |
Salami, chorizo, fish sauce, fermented shrimp paste |
Why fermented soda?
Fermentation is why our drinks taste the way they do. The subtle tang and the depth of flavour come directly from the work of live microorganisms, not from additives or artificial flavours.
Every batch is brewed slowly, relying on the natural activity of lactobacilli to create depth and balance. Once fermentation is complete, we gently pasteurise our sodas to stabilise flavour and ensure safety, while preserving many of the beneficial compounds produced during fermentation.
Even after pasteurisation, many of the organic acids, short-chain fatty acids, and bioactive compounds created by our fermentation process remain active.
We love collaborating with nature to create a soda that’s rooted in thousands of years of tradition and packed full of flavour.
Keep it fermented. Keep it Good™.
Fermentation FAQs
Just in case you had any leftover questions about fermentation.
Is fermented food safe to eat?
Absolutely. Done right — the correct pH, temperature, and hygiene — fermentation is a very safe process. The acidic environment it creates actively fights off harmful pathogens. People across every culture have been eating fermented food for thousands of years. It helps keep food Good™.
Does all fermented food contain alcohol?
Nope. Alcoholic fermentation (the yeast kind) produces ethanol, but lactic acid fermentation doesn't. Yogurt, kimchi, sauerkraut are all fermented and all alcohol-free. Some drinks like kombucha carry trace amounts from the yeast in the SCOBY, but at very low levels. Good Sodas™ use lactic acid bacteria, so they're completely alcohol-free.
Are all fermented products probiotic?
Not quite. To be probiotic, a product needs live, active microorganisms in adequate quantities and ones with demonstrated health benefits. Pasteurisation kills the live cultures, so pasteurised fermented products don't count. And even among raw, unpasteurised ferments, not every strain does the same thing.
What's the difference between fermented and pickled?
Pickling uses vinegar to preserve food. No live microorganisms means no fermentation. Kimchi and sauerkraut, though? Fermented. Made with lactic acid bacteria, the same way Good Sodas™ are made.
Good™ to know: vinegar itself is made through fermentation but it’s so acidic it kills any further microbial activity in the pickles.