Why fermentation isn’t always fermentation

At the contemporary food scene we’ve been witnessing the movement from the molecular gastronomy of the late 1980s and onwards to a biological gastronomy – and to see the uprising in fermented foods and beverages at the moment is truly fascinating.

As a brewery, fermentation is naturally the core of our production at To Øl: Without it you would only taste overly sweet, dull, flat beverages with no interest.

But when we talk fermentation as a specific method, it needs to be defined right – so here goes the overly educational textbook fermentation guide from our own brewery lab experience to you people out the in the kitchens of biological gastronomics of the world.

Fermented food can be achieved with yeasts and bacteria. We all know that the majority of fermented foods is produced by lactic acid bacteria and yeasts, but it can also be performed by moulds. (There is a long story about the difference between yeast/mould and bacteria, eukaryotic cells vs prokaryotic cells but we’ll save that tale for a rainy day).

In fact fermentation cultures is really at matter of breathing and breaking down nutrients:

A microorganism has two options for the breaking down of nutrients (substrate): Fermentation and respiration. Simply put, respiration is what happens in your muscle cells while running and fermentation is what happens when you sprint (creating lactic acid).

If you feel like showing off to your friends how much you know about fermentation, make use of this sentence from 1597 by Andreas Libavius (one of our founding fathers in regards to fermentation as a gastronomic method): “Fermentation is the exhalation of a substance through the admixture of a ferment which, by virtue of its spirit, penetrates the mass and transforms it into its own nature.”

To rephrase Libavius the real biochemical definition of fermentation is to have Substrate level phosphorylation. This means that while many processes might improve or change the flavour of a certain product, scientifically speaking they’re not actually considered real fermentations but respirations.

Most fermentation processes are cultivated in airtight containers with no oxygen. We call these processes anaerobic. In these environments only lactic acid bacteria and facultative yeasts will prosper. However, most yeast will actually grow better under aerobic conditions, but it will not make the yeast produce the necessary alcohol and aroma compounds.

When it comes to lactic acid bacteria (LAB) – the basis of most fermentation processes – we’re basically talking about two types of fermenters: Homofermenters and heterofermenters. The homofermenters produce lactate as virtually a single product from the fermentation of glucose. Heterofermenters produce roughly the same amounts of lactate, ethanol/acetate and carbon dioxide from glucose.

Considering for example the production of vinegar – it is in fact a special case, because strictly scientifically speaking the ethanol oxidizes to vinegar and is therefore not really fermented by acetobacter and gluconobacter bacteria.

So basically: In the eyes of fermentation purists as ourselves as brewers – the production of vinegar is strictly speaking not fermentation, but a product of respiration.


Here we might as well use the opportunity to expose the general fallacy of grouping tea as a fermented product: Most teas are the results of enzymatic oxidation processes, unless they specifically underwent a fermentation process leading them to become fermented teas.

Still doesn’t mean we don’t enjoy both vinegar and other wonderful pseudo-fermented products like pickles, malo-lactic fermented wines and specific mould cheeses here at To Øl.

For the continuous exciting development of the biological gastronomics we’ll just throw a loving glance at science helping us get our definitions in order.