In the previous article of this series, we discussed malting, the first step of the Whisky production process.
The next operation is then to extract the sugars from the malt.
The malt is taken from the silos, where it must remain for several weeks after malting to complete drying, and immediately ground in a mill. It is then covered with hot water to extract as much of the maltose it contains as possible.
The malt is then ground by a roller mill, and adjusted so that the result, the grist, is composed of 20% from the grain hulls, 70% from coarse whole-wheat flour, and 10% from refined white flour.
The extraction of the sugars, the maltose, takes place in large vessels, similar to large pressure cookers and usually made of steel, called mash-tun. The grist is fed into these tanks via a hopper at the same time as the first hot water. The bottom of these tanks is a large strainer that allows this grain ‘mash’ and water to percolate, causing the sugars to be extracted. The collected must, the wort, is a dark, very sugary liquid. This operation is repeated several times, usually with water at increasingly higher temperatures (usually three times at 70° 80° and 90°), to make sure nothing is wasted.
The first and second water go on to fermentation. The third water, which contains very little sugar, is stored and then reused as the first water for the next mashing. The grain that eventually remains inside the mash-tun, the draff, is still very rich in protein. It is therefore not wasted, but harvested and processed into livestock feed.
The wort is then cooled to a temperature of about 16°; higher temperatures would in fact risk killing the yeasts in the next fermentation stage, which we will discuss in the next article.
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