To saccharify means to convert to sugar. In whisky distilling it refers to the process which takes place during the malting and mash-tun stages by which enzymes in the malt, referred to as diastase, turn the starch in the cereals into sugar ready for the fermenting action of the yeast.
When conditions of temperature and moisture favour germination, the embryo and associated parts of the barley grain secrete a mixture of enzymes commonly known as diastase. These act to modify and make soluble the starch in the barley, thus preparing it for conversion at a later stage to maltose.
Wort is the liquid drawn off the mash-tun in which the malted and unmalted cereals have been mashed with warm water. Wort contains all the sugars of the malt and certain secondary constituents. After cooling, it is passed to the fermenting vats. In Malt distilleries the cereals are all malted; in Grain distilleries a proportion only is malted, the remainder being unmalted. In some cases, Grain distilleries do not separate off wort, passing the complete mash to the fermentation vessels.
The wort or mash technically becomes wash as soon as yeast is added to start fermentation. However, the term is usually used to refer to the liquid at the end of the fermentation. It is the wash which forms the raw material of the first distillation in the Pot Still process and of the only distillation in the Patent Still process.
Malt Whisky is distilled twice – although a few distilleries may undertake a third distillation – in Pot Stills which resemble huge copper kettles.
The spirit is driven off from the fermented liquid as a vapour and then condensed back to a liquid.
In the first distillation the fermented liquid, or wash, is put into the Wash Still, which is heated either directly by fire or by steam-heated coils.
At this stage the wash contains yeast, crude alcohol, some unfermentable matter and the by-products of fermentation. During the process of boiling the wash, changes take place in its constituents which are vital to the flavour and character of the whisky.
This condenses the vapours and the resulting distillate, known as low wines, is collected for re-distilling. The liquor remaining in the Wash Still is known as pot ale or burnt ale and is usually treated and converted into distillers’ solubles for animal feed.