🥃 Mashing

Mashing is the stage of whisky and other grain spirit production when crushed malt is mixed with hot water. The malt's enzymes, amylases, break down starch into sugars, mainly maltose, and the result is a sweet liquid called wort. Yeast then ferments the wort, and the wash is distilled. Without mashing, the grain would give no alcohol.

How it works. The malt is milled so that about 20% is husk, 70% grits and 10% flour. Too fine a grind clogs the filter, and too coarse a grind releases sugar poorly. The grist is mixed with water in a mash tun. Most distilleries now use stainless steel tuns with rotating knives, while old rake mash tuns survive, for example at Springbank and Bruichladdich.

Several waters. The first water is about 63–64 °C: at this temperature the enzymes work best, while above 65.5 °C they start to break down. The second water is hotter, up to 75 °C, and the third is 85–90 °C: it washes out the remaining sugar but kills the enzymes. Some distilleries add a fourth water up to 95 °C. The last waters are used as the first water for the next mash, and the wort is cooled and pumped into fermentation vessels.

Flavour and leftovers. According to Difford's Guide, a cloudy wort with husk particles gives a nutty, spicy, malty spirit, while a clear wort gives a less grainy one. Some peaty phenols are lost with the grain. This protein-rich spent grain is sold as cattle feed or burned as fuel. For bourbon, a mix with corn is mashed, and the sour mash method adds acidic spent wash to the mash.

Why this matters to you. Mashing determines how much spirit the grain will give and how the whisky will taste. Words like sour mash or mash bill on labels refer to this stage. But no mashing method makes a strong drink safer. The WHO reminds us: there is no safe level of alcohol.