Fermentation - How it all works

I briefly touched on concepts like distillation and fermentation in my last two pieces, but deliberately glossed over them because an understanding of the concepts isn't really vital to understanding whisky. However, it is worth noting that to appreciate the finer differences in many spirits, beers and wines, it is worth understanding the process of turning anything in the world containing sugars into delicious alcohol.
Fermentation is the beginning of the process. Ferment comes from the latin word fervere, which means to boil. This is is a bit of a confusing origin, as their is no boiling that occurs during fermentation. However! Fermentation, while happening in massive vats for the creation of a spirit, does create carbon dioxide, which bubbles to the surface of the liquid, which cause it to froth (as if the liquid were boiling, and hence the term).

Fermentation all starts with little fungi called yeast. Unlike other fungi like mushrooms which grow from nutrients in the ground, or parasically on the sides of other plants using the plant's energy for food, yeast is more like a 4 year old child at Easter. All it wants to eat is sugar. Unlike 4 year old at Easter, however, yeasts's waste products after consuming sugar are alcohol, heat and carbon dioxide.

Not a good home-brew investment

When introduced to a sugary liquid, yeast will start to break down any sugar molecules (including longer chain molecules like starches and carbohydrates which are complex sugars). While breaking these down, the yeast will create ethyl alcohol (as well as several undrinkable alcohols like methyl alcohol), as well as acids, esters and fusel oils which all contribute to the aroma and flavour of the alcoholic beverage that results. It will also create heat in small amounts, and carbon dioxoide (which is why beer and champagne are fizzy. The carbon dioxide is captured in either the barrel it is fermented in, or the bottle it is fermented in). When all the sugar has been turned into alcohol, the yeast cells start to starve and die. You know the sediment at the bottom of a Coopers Pale Ale stubby? That sediment is the left over yeast from the fermentation process. Most of the major commercial breweries will sell their left over yeast sediment as yeast extract to make everyone's favourite breakfast spread, too (which should be a great way to get your kids to eat more of it!).

Another good parenting technique

Beer and wine are the most common fermented beverages that we drink. The reason that most wines aren't carbonated is because the carbon dioxide is allowed to escape while it is fermented, because the vats are open topped. Most modern beers are artificially carbonated as well by the time we get to drinking them, but they do have natural bubbles to them.

The differences in flavour in fermented drinks is determined by two things: the source of the sugar and the strain of yeast. It stands to reason that wine, which is made from grapes, is going to taste different to beer, which is made from barley grains. This goes for all fermented drinks. Different varietals of grapes will taste different on their own, and will therefore taste different when they are fermented. However, the strain of yeast that does the fermenting is going to change the flavour slightly too.

Some popular brands that you regularly drink will hold that their super secret yeast strain is the key to the flavour profile of their beverage. Jim Beam bourbon, Bacardi rum - these guys are really proud of their yeast strain. According to the Bacardi master distiller, all the flavours that you can possibly create for booze come from that first important step of fermentation. The strain of yeast used is responsible for the creation of those flavours. Some yeast strains act really quickly on the sugars, resulting in a fast, hot fermentation period. This quick process doesn't allow many flavours to develop. However, a longer fermentation period (some Jamaican rums like Appleton Estate have ferments that last for almost a week) will cause lots of esters to form, hence, more flavours and aromas.

There are lots of factors that will affect the end result in a fermented drink. Yeast is a living organism, and as such, will die if it is exposed to undesireable environments. One of these is alcohol itself! Yeast cells start to die if the alcohol content of the liquid they are in reaches about 18% (which is why you won't get wine or beer that is higher than this. Most wines only go to about 14 - 16%, and most beer is to around 8% max), but typically fermentation will be ceased well before this point. Other things like too much heat or not enough will also cause yeast cells to die. They will also exhaust themselves by trying to consume too much sugar at once (similar to that 4 year old at Easter - come lunch time they all have sore tummies really, really just want a fucking carrot or something).

So really, in a nutshell, think of fermentation like this.
Step 1: Add water and sugar and yeast together in a bucket.
Step 2: ????
Step 3: Profit! (In the form of alcohol)

Master home brewers

Drink on.