What Is Fermentation? The Ancient Science Behind Modern Drinks

There was a time, long before refrigeration or pasteurisation, when human beings faced a fundamental question: how do you preserve food in times of abundance? Some turned to salt; others relied on simple containers. What they discovered, often by accident, was that these methods did not merely prolong the life of food: they transformed it into something else entirely.

By leaving grains to soak in vats of water, the ancient Egyptians stumbled upon beer. Nomadic peoples of the Caucasus discovered kefir by fermenting milk in animal-skin bags. Ancient Persians found wine in clay vessels filled with ripened grapes. Across different cultures and continents, people were unknowingly harnessing the same invisible force and, without realising it, they had uncovered one of humanity's most transformative discoveries: fermentation.

What is fermentation?

Fermentation is the process through which microorganisms - bacteria, yeasts, and moulds - convert sugars and other compounds in a liquid into substances like alcohol, carbon dioxide, organic acids, or a combination of these. The result is something fundamentally transformed: different in taste, texture, and aroma from what it started as. It is the process that turns milk into yogurt, soybeans into miso, and sweetened tea into kombucha.

What makes fermentation remarkable is not just the science, but the craft. The finest fermented drinks, like the finest wines, are the result of careful decisions about ingredients, microbial cultures, temperature, and time. Small changes produce vastly different outcomes, which is why no two batches are ever quite the same.

What types of fermentation exist?

• Alcoholic fermentation: In the absence of oxygen, yeasts and some bacteria convert sugars into alcohol and carbon dioxide. This is the mechanism behind wine (from grape juice) and beer (from malted barley). It is the most widely known form of fermentation, but far from the only one.
• Lactic acid fermentation: Unlike alcoholic fermentation, lactic acid fermentation is carried out by bacteria of the Lactobacillus genus, which convert sugars into lactic acid rather than alcohol. It is the process behind the transformation of milk into yogurt or kefir, and it produces the characteristic gentle acidity that makes these foods so distinctive.
• Alcoholic, lactic acid, and acetic fermentation (combined): This layered combination of processes is what makes kombucha so complex. Yeasts first convert the sugars in sweetened tea into alcohol. Acetic acid bacteria then convert that alcohol into acetic acid, while lactic acid bacteria may also produce lactic acid alongside it. The result is a drink that is slightly acidic, gently effervescent, and layered with flavour in a way that reflects every variable in its making.

What is a non-alcoholic fermented drink?

While wine and beer remain the most widely known fermented drinks, the category extends far beyond alcohol, and that side of it is growing fast. Non-alcoholic fermented drinks like kombucha, water kefir, and ginger beer demand the same knowledge and craft as their alcoholic counterparts: the same careful control of cultures, temperature, and time. What they offer in return is a flavour profile that is genuinely complex: tart, layered, and alive, with none of the side effects. It is precisely this combination of craftsmanship and accessibility that is making them increasingly sought after, both in mixology and among those simply looking for something worth drinking that isn't wine.