This is normally done three times at 60, 72 and 88 degrees. The wort is pumped into a brew tank called a washback, yeast is added and the fun begins.
The yeast feeds on the sugar and makes carbon dioxide and alcohol as a by-product. If you added hops you would have lager. The brewing process is very carefully controlled because it can affect the final flavor of the whisky. In some cases, if the conditions are suitable, wild yeast may also be introduced. Whisky Production - Step 1 — Fermentation May 01, Malting The first step is to malt the barley grain. Germination This is halted after 3 to 5 days by drying the grain with hot air once the optimum amount of starch has been converted to sugar.
Mashing The dry malt is then put through a gristmill to make it into coarse flour called grist. Brewing The wort is pumped into a brew tank called a washback, yeast is added and the fun begins.
After 48 to 50 hours the yeast will have made alcohol and when distilled the resulting spirit will tend to have a cereal taste. Fermentations lasting longer than 60 hours take advantage of the yeasts dormant resting period when it produces new flavours resulting in a more complex spirit. Longer fermentations over 55 to 60 hours with standard distiller's yeast produce little or no more alcohol, but the longer the fermentation the more flavour that is likely to be generated. Longer fermentations also tend to produce a wash that's easier to distill as they have less of a tendency to foam see distillation.
At its height the amount of carbon dioxide generated by fermentation produces a significant amount of foam and most distilleries have 'switcher blades' spinning around the top of their washbacks which repeatedly knock the top of the foam and prevent the fermenting wort from coming over the side of the washback. Emergency anti-foamer is usually also sighted nearby for adding in emergencies.
From until , all Scottish whisky distillers were obliged by the Scotch Whisky Association to use the same yeast strain DCL M-strain , a yeast originally hybridized from Saccharomyces cerevisiae and Saccharomyces diastaticus during ss by what we know today as Diageo for its ability to break down maltose sugars, for being good at making alcohol and producing the flavours associated with Scotch whisky.
Distiller's yeast is available in liquid 'cream', pressed semi-dry and dried forms. Liquid yeast is cheaper and easier to handle but dies after only a few weeks, while dried yeast can be stored for years. Most distillers prefer to use liquid yeast but keep stocks of dried yeast as a backup.
Few, if any, Scotch whisky distillers propagate their own cultures. Yeast cells move around within the washback during fermentation due to secreting carbon dioxide as the yeast makes alcohol in such a way that the ejected gas acts like a jet propulsion system to keep the cells on the move. The yeast used by distillers is similar if not the same as brewer's ale yeast, known as top flocculating yeast due to its floating to the surface when spent rather than sinking to the bottom of the fermentation vessel.
Second-hand beer brewer's yeast although very messy to handle is used by a few distillers due to its low cost and high acidity which increases beneficial copper reaction during distillation. Continue reading : 7. JavaScript is not enabled! Modern stainless steel washbacks use automatic cleaning systems and less chemical treatment is required than it is for cleaning wooden washbacks. Some modern distilleries use cooled washbacks that can regulate the temperature of the mash.
They are closed systems in which fermentation process and activity of the yeast can be influenced as well as developing byproducts. What happens inside the washbacks when yeast is added to the wort? To put this formula in words: In our wash there are glucose molecules. The yeast now spits them and each molecule gives two ethanol molecules which is the alcohol we need , two carbon dioxide molecules and heat. Carbon dioxide rises up, what causes the bubbles in the mash and produces the foam so the carbon dioxide itself cannot be seen, but the reaction it causes.
Some distilleries that have closed washbacks gather these gases. But: Besides of these three primarily products there are many other byproducts of fermentation.
Distillers know that they can influence the aroma of the Whisky by the length or the temperature of the fermentation. Especially in a second part of fermentation, when the activity of the yeast calms down, aromatic complexity can be reached.
Primary fermentation will come to an end when there is no more sugar for the yeast to transform and the alcoholic concentration of the wash rises to high. At this stadium, when the alcohol hinders the yeast from being active, several bacteria will start to work, especially lactic acid bacteria.
The chemical reactions these bacteria push will end up with new compounds. These are acids, aldehydes, esters and long-chain alcohols. They make up a small amount, but they have influence the aroma and the body of the wash. As most of them are not lost during the following distillations it would be a big mistake to pay no attention to them. The length of fermentation varies from distillery to distillery. After 48 to 96 hours it will be finished and the mash will end up with an alcohol concentration of about 6 to 10 percent.
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