Fermentation: The Ancient Alchemy of Alcohol

The Latin word fervere, meaning "to boil or seethe," is the root of the English word "fermentation." Since the bubbling and foaming of early fermenting beverages resembled boiling, it was given this name. However, fermentation doesn't need heat like boiling does. It is a subdued chemical reaction, a metamorphosis that elevates simple sugars into something much more potent.

So what is fermentation, really?

Fermentation is a natural process where microbes like yeast, molds, and bacteria use their enzymes to break down complex materials into simpler, easier-to-digest compounds. But the type of microbe and the end product are different. 

In foods like yoghurt or kimchi, bacteria do the work: they turn sugars into lactic acid, which gives those foods their tangy taste and helps preserve them. In drinks like beer, wine, and spirits, brewer’s yeast (Saccharomyces cerevisiae) takes over instead of bacteria. A basic recipe consisting of sugar, water, and yeast is used to start the process. When you combine them in an oxygen-free atmosphere, the yeast ferments sugar for energy, creating ethanol – the type of alcohol that enables the production of alcoholic drinks.

Fermented drinks in history and culture

Fermentation is among the earliest biochemical processes that humans are aware of. According to archaeological evidence, people in China were fermenting drinks as early as 7000 BCE using fruit, rice, and honey. Beer was brewed by the Sumerians in 4000 BCE. Wine was produced by the Egyptians in 3000 BCE. And it was all propelled by wild yeast, which landed on grapes, grain, and fruit while floating undetectably through the atmosphere.

In fact, early fermentation was often an accident. A bunch of overripe fruit left out in the sun could easily turn into a simple wine. The yeast was already there, waiting. It just needed sugar and time. 

A few thousand years later, people started to do fermentation on purpose. Cultures started to grow yeast, improve their methods, and try out different substrates. People tried to ferment anything that had sugar in it, like palm sap, barley, corn, and agave.

Wild yeast is everywhere — on fruit skins, grains, plants, and in the air — and different places have different strains. Each strain creates its own mix of flavors during fermentation, which is why drinks made with wild yeast often taste unique to their location.

When looking at fermentation, one cannot discount the cultural aspect of it. Fermented drinks are more than just drinks in many cultures. They stand for celebration, tradition, and identity. Sake in Japan, pulque in Mexico, chicha in Peru, and kvass in Russia. Each has a unique fermentation tale that is influenced by regional ingredients and traditions.

Consider pulque. It predates tequila by centuries and is made from the fermented sap of the agave plant. Wild microbes found in the sap and the surrounding environment are what cause the spontaneous fermentation. Unlike the clear, high-proof spirits we now associate with agave, it is hazy, sour, and slightly viscous. However, it has deep historical and ritual roots in Mexico.

Or consider kvass, a fermented rye bread beverage with a low alcohol content popular in Eastern Europe. It is frequently made from scratch using recipes that have been handed down through generations. A slight fizz and tang are produced by the brief fermentation. It has nothing to do with getting wasted. It all comes down to flavour, custom, and refreshment.

The science of fermentation

In the 1850s, French chemist and microbiologist Louis Pasteur was the first to demonstrate that yeast was responsible for turning sugar into alcohol. Fermentation was regarded as a mysterious "vital force" before that.

Fermentation begins with glycolysis, a process where sugar is broken down into pyruvate. Without oxygen, pyruvate turns into acetaldehyde, which then becomes ethanol — the alcohol we drink. This also releases carbon dioxide, the gas that makes beer fizzy and bread rise.

While this no-oxygen process works well, it isn’t perfect. Yeast also creates small amounts of other compounds, such as fusel alcohols, esters, and aldehydes. These, called congeners, influence flavour and aroma — some in pleasant ways (like fruity notes in Belgian ales) and others less so (like methanol, which can cause hangovers).

Controlling these factors is the art of fermentation. Yeast strain, temperature, pH, and nutrient availability all affect the process. A study published in Frontiers in Microbiology in 2020 showed how metabolic flux and gene regulation affect fermentation results. It's less of a science experiment and more of Beethoven's Moonlight Sonata.

Furthermore, not all yeast strains are made equal. Although the main force behind the production of alcohol is Saccharomyces cerevisiae, other strains like Brettanomyces (or “Brett”) and Lactobacillus also add to the funkiness of wines and the sourness of beers. The flavour profile and alcohol content are both impacted by the yeast selection. Do you want a crisp lager? Make use of a yeast that prefers cooler temperatures (aka bottom-fermenting). Do you like your IPA fruity? Select a strain that prefers warmer temperatures (aka top-fermenting).

Each beverage has a different fermentation process. Malted barley is usually used as the sugar source for beer, and hops are added for flavour and aroma. The sugars in grapes are what make wine, and fermentation takes place in oak barrels or stainless steel tanks. A fermented mash (corn for bourbon, rye for whisky, or agave for tequila) is the starting point for spirits, which are then distilled to concentrate the alcohol.

Modern fermentation

Modern breweries and distilleries now use sensors and software to watch the fermentation process closely, helping them get better quality and more alcohol. It’s a big change from the old days of clay pots and wild yeast.

However, fermentation is still somewhat of a mystery in spite of all this technology. Yeast is a living, breathing thing. It reacts to its surroundings, adjusts to stress, and occasionally exhibits unpredictable behaviour. Because of this, human intuition is still used in even the most sophisticated distilleries. Even if the data indicates otherwise, the master distiller or brewer is aware of when a batch is "off."

Fermentation has an impact on spirits as well. The mash's composition, fermentation time, and yeast selection all play a big part in the character of the final product. A well-fermented mash will yield a whisky with character, depth, and complexity. A badly fermented one? Forgettable, harsh, and flat.

Therefore, keep in mind the unsung hero behind it all the next time you raise a glass of wine or take a dram of single malt. The magic starts with fermentation. It is the ancient alchemy that transforms fruit into firewater, grain into glory, and sugar into spirit.

Ultimately, fermentation is the unsung hero at work in the background, even though distillation may receive all the attention. Let's toast to that.