Yeast is the star of the alcoholic drinks industry - a tiny, single-celled organism that likes to consume sugar. If it is encouraged to feed in the absence of oxygen it releases two waste products: carbon dioxide and ethyl alcohol or ethanol – the drinkable form of alcohol, and the ingredient of many a night out.
This fermentation process has been adapted in many ways to produce the dazzling array of drinks found on the shelves of any off-licence.
At the vineyard When yeast is added to crushed grapes at the vineyard it starts consuming the natural sugars in the flesh of the fruit. This process carries on until all the sugar has disappeared when the yeast will die. The resulting beverage (with a bit more processing) could be the perfect Pinot Grigio or the best Beaujolais depending on the type of grape used.
Bitters use different yeasts
Beer - lager, ale, stout, bitter etc At the brewery, barley, water, hops and yeast come together to make beers and lagers. Yeast comes in many strains, each with specific charecteristics. In general, British beer needs a top-fermenting yeast while lager needs bottom-fermenting.The sugar that is fermented comes from the barley - a grain that looks like wheat and is specially treated so that it starts to sprout. At this stage the germination is halted by drying and then kilning to ensure the malt is brought to the desired colour. Hops are added for their flavour and to prevent the growth of certain bacteria, which might cause the beer to spoil.
Producing spirits In the distillery, an already fermented drink is treated to increase its percentage of alcohol. The hard drinks whisky, vodka, gin and rum are produced this way. When an alcoholic mixture is slowly heated towards boiling point the ethanol steams off first. When vapour is collected at the right temperature it has a higher alcohol content than the original liquid.
The downside is that taste deteriorates in the distilling process although it can be improved by maturation. Pricey single malts will sit around for decades allowing a slow chemical process to take place, which breaks down large organic molecules (the 'nasties' in the drink) into flavour-enhancing chemicals.
Distillation increases the percentage of alcohol