Glossary
Mash
Steeping milled malt in hot water so that the grain’s own enzymes convert its starch into fermentable sugar.
Also called mashing, mash in.
Malt is mostly starch, and yeast cannot ferment starch. The mash is where amylase enzymes — developed in the grain during malting and preserved by careful kilning — cut those long starch chains into sugars the yeast can use.
Temperature is the brewer’s main control. The two relevant enzymes have different optima: beta-amylase, most active around 60–65 °C, produces highly fermentable maltose; alpha-amylase, most active around 68–72 °C, produces more unfermentable dextrin. A cooler mash therefore makes a drier, thinner beer and a hotter mash a sweeter, fuller one from the same grain.
Related
- Mash temperature — The lever that decides fermentability.
- Wort — What the mash produces.
- Diastatic power — The grain’s capacity to do the conversion.
- Lautering — Separating the liquid from the grain afterwards.
More vocabulary
Arrested fermentation · Barrel ageing · Batch sparging · Biotransformation · Blending · Bottle conditioning · Bottom fermentation · Burtonisation · Cask conditioning · Centrifugation
See every term on the glossary index.
Last reviewed 2026-08-16.
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
The rule that grain holds about 0.4 times as much heat as water, which every strike-water calculation depends on, matches measured barley at kilning moisture — but it rises with moisture content and carries roughly 8% measurement error, so a strike temperature is an estimate rather than a setting.
Checked against the source
Source: Łapczyńska-Kordon et al., "Thermal Characteristics of Barley and Oat" (1994), Table 1, barley specific heat regression; measurement errors, p. 275 (Int. Agrophysics 8:271–275)