mash is the mixture of milled grains and hot water that is created at the beginning of the brewing process that leads to fermentation and distillation. “The mash” can also refer to the “mash bill”—the blend of different grains used in American whisky distilling. Mashing is the carefully controlled cooking of this mixture of grains and water, which chemically converts the starches in the grains into fermentable and unfermentable sugars, an essential step on the way to fermentation. See mashing.
Mashes differ from country to country and often from distillery to distillery. Mashes made up entirely of malt are the easiest to work with and the oldest. Many distilling traditions, however, use a little malt to start saccharification (15 percent will do) and round the rest out with raw grains. Rye, which is common, and oats, formerly used in Ireland and now enjoying a small revival, are the most challenging to work with, as they are quite glutinous.
To start the mash, the grains are milled to a flour-like consistency in order to expose as much surface area as possible to the water and the enzymes, allowing a full and fast conversion. A successful mash begins with a careful and full hydration of the flour as it goes into the mashing vessel. This wet mix of grain flour and hot water is referred to as the “grist”; only once enzymes, either from included malt or added by the distiller, have converted the starches in the grain to sugars does the thick, starchy, and sticky grist become the much more liquid mash.
Mash can be further refined into “wort” by filtering out the remaining solids; this is the practice in Scotland and Ireland and wherever grain distillers have adopted their model. In Germany, however, the mash is traditionally distilled without filtration, and America has always followed this model. See wort.
Mashing different grains comes with different challenges. Malted barley is relatively simple and straightforward. See barley. Rye and wheat, on the other hand, have a lot more proteins, which will cause the mash to clump and stick together. See rye and wheat. Careful temperature management and addition of beta-glucanase enzymes will help with this, and will also cut down on the notorious excessive foaming in rye fermentation.
See also
Bamforth, Charles. Beer: Tap into the Art and Science of Brewing. New York: Insight, 1998.
Broom, Dave. The World Atlas of Whisky, 2nd ed. London: Mitchell Beazley, 2014.
Buxton, Ian, and Paul S. Hughes. The Science and Commerce of Whisky. Cambridge: Royal Society of Chemistry, 2013.
By: Lew Bryson