What is mashing in whisky?

Mashing is the mixing of ground malt with hot water, so that the enzymes in that malt convert the starch into fermentable sugars.

The ground malt is called grist. For malt whisky it is ground more coarsely than for beer. A common split is about 20 percent coarse husk, 70 percent medium and 10 percent flour. That milling keeps the grain bed in the mash tun permeable, so that the liquid can drain through.

The grist goes into the mash tun together with hot water and is stirred there by arms or blades. After a few hours the starch has largely been converted and the sweet liquid drains away through the sieve bottom.

A mashing round proceeds in successive pourings of water that get hotter each time, because the enzymes in malt work at different temperatures.

The first infusion is at around 62.5 degrees Celsius. At that temperature the enzymes in the malt work best; the two most important are beta-amylase and alpha-amylase, which together break down the starch into sugars that yeast can work with.

The second water addition is about 75 degrees and the third around 85 degrees. That releases sugars that were still locked in at the first addition. The last addition goes towards 95 degrees and rinses the grain bed.

That last water is too thin to ferment on its own. A distillery therefore keeps it and uses it as the first pour for the next mash, so that no sugar is lost.

Wort is the sweet liquid that runs out of the mash tun, spent grain is the exhausted grain bed that is left behind.

The wort is cooled before it goes to the washback, the vat in which the yeast does its work. Cooling is necessary, because yeast does not survive at mashing temperature.

Draff, called draf in Dutch, consists of the moist grain residues that remain in the mash tun after draining. The material is rich in protein and in Scotland usually goes as cattle feed to farmers in the area. A distillery is left with tonnes of it per mashing round, so it is a serious by-stream and not waste.

With Scotch whisky that is not allowed: the rules require that the conversion be done with the enzymes already present in the malt.

The Scotch Whisky Regulations 2009 prescribe that Scotch is made from water and malted barley, to which only whole grains of other cereals may be added, and that at the distillery this is converted into fermentable material only by the malt’s own enzymes. Distillation below 94.8 percent alcohol follows, at least three years of maturation in Scotland in oak casks of at most 700 liters, and bottling at no less than 40 percent.

The European definition is broader. For whisky, Regulation (EU) 2019/787 permits conversion with the diastase from the malt itself, with or without other natural enzymes. The American standard for whisky, 27 CFR 5,143, sets no requirement at all regarding enzymes.

In de winkel aan de Brink 2 in Bathmen staan 3.897 verschillende whisky’s: 2.782 uit Schotland, 322 uit Ierland, 163 uit de Verenigde Staten, 117 uit Japan, 115 uit Nederland, 55 uit Belgie, 46 uit Engeland, 42 uit Frankrijk, 41 uit Taiwan en 38 uit India. NIX18: wij verkopen geen alcohol aan iemand onder de 18 jaar.

With beer, the wort is boiled and hopped after mashing; with malt whisky neither happens.

A brewer boils the wort and adds hops. A distillery, by contrast, cools the wort and lets it run unboiled to the washback, where only yeast comes into play. The Scotch Whisky Regulations name only yeast for fermentation, so hops or other additions do not go in.

Furthermore, a brewer mills finer than a malt distillery, and a distillery steers mainly on sugar yield and clear wort, not on foam or bitterness.

Of the Scottish bottles in Bathmen, 723 come from Speyside, from 82 brands, 495 from Islay, 456 from the Highlands, 109 from the Islands, 104 from the Lowlands and 70 from Campbeltown.