I can hear people getting confused quite often, differentiating what’s been fermented from what’s been distilled. Here is the basic difference explained to you:
Common fermented drinks include wine, beer, sake or cider. Fermentation is the process where the natural sugar that’s present in the main ingredient (glucose andfructose in grapes and apples, starch in grain…) is converted into alcohol & CO2 under the action of yeast.
Let me explain, whether it is a beer or a glass of wine you’re drinking, it contains yeast. The most commonly found types of yeast belong to two families: Saccharomyces Cerevisiae & Saccharomyces Uvarum. When the grapes were crushed, or the grain boiled, the juice that came out of it (known as “must”) was a sweet liquid. The yeast, either naturally occurring or added by the maker, has been feeding on that sugar and releasing alcohol and CO2 in exchange.
The alcohol remained in the liquid but the CO2 had two ways to go. If the fermenting vessel (a bottle, a barrel, a tank…) was open, then the CO2 had no choice but to go away, resulting in a still liquid. However, in the case of a closed fermenter, the gas would divide itself into smaller and smaller bubbles to occupy the volume, making the liquid sparkling.
Beer VS Bread: Ingredients are very similar for both beer and bread, and the idea behind them is the same. When yeast is added to the grain, feasting on its sugar, we know that both alcohol and CO2 will be released.
In the case of bread, the dough is placed in a hot oven, where the alcohol will evaporate but the CO2, trapped, will make the dough rise.
In the case of beer, the must is placed in a fermenter where the alcohol will stay in the liquid but the CO2, first, will be released. A secondary fermentation, in the closed bottle, will trap the last bit of CO2, making the beer sparkling.
Common distilled drinks are all spirits (such as whiskey, gin, vodka, brandy, Calvados, tequila, etc…). Distillation is going one step further. First, we’ll start from a fermented drink, let’s take one concrete example with whiskey:
Step 1: The maker will start by brewing something very close to a beer, but without hops (which are responsible for bitterness in beer).
Step 2: This liquid, once fermented, will be poured into a pot still (other types of distillations exist, but for argument’s sake, let’s say a pot still).
A traditional distillery
If you think of a standard beer at 5% ABV, that means that about 5% of the drink is pure alcohol and that about 95% is water. If you wish to extract the 100% ABV pure alcohol, the best solution is to heat it up, which leads to our step 3:
Step 3: The idea is to concentrate the alcohol content of the drink and get rid of the water content and of other elements. In the case of a pot still, the liquid will be heated through a pipe, until it reaches the very precise temperature of 78˚C. At that stage, the ethanol will evaporate (which is the “good alcohol”, meaning the one you can consume in reasonable quantities without going blind or insane). In a pot still, this steam of ethanol will then be quickly cooled down in order to go back to a liquid shape. Drops are then collected and the process can be repeated a few times to extract the purest ethanol.
The danger: Other types of alcohol and other elements will also evaporate at other temperatures. The most famous one is probably Methanol. Although its name is quite close to the “good” ethanol, this alcohol is extremely dangerous for health, with severe complications for its drinkers. Methanol is extracted at 64˚C. Therefore, it will drip out of the pot still first, before the ethanol. Other undesirable elements will be extracted at higher temperatures, leading to an ancient saying that “one should throw both heads and tails while distilling”. That is to say that what comes out first and last is not to be kept for consumption, but only the ethanol in the middle.
If we go back to a standard beer containing about 5% alcohol, that is to say 5cl in a litre. You would need 20 litres of that beer to produce 1 litre of pure alcohol (100% ABV). To produce whiskey, usually labelled at 40% ABV, the pure alcohol would be watered down to reduce its strength by more than half.
That is the basic difference between fermentation and distillation. Like I said, other ways of distilling drinks exist, one that is quite often found is Freeze Distillation, which is done by repeatedly freezing the water content of an alcoholic drink and scooping out the non-frozen pure alcohol. The result is quick but the methanol and other undesirable elements are left in the spirit, making it extremely dangerous for human consumption. A traditional example is Applejack in the US.
Certified Sommelier (CMS)