Mashing: temperatures, time and steps

What happens in the mash

Malt contains starch and the enzymes able to break it down. Two enzymes do most of the work:

• Beta-amylase, active mainly between 60 and 65 °C, produces maltose, a sugar that yeast ferments. A mash at 63-64 °C gives a drier beer.
• Alpha-amylase, active mainly between 68 and 72 °C, cuts starch into larger pieces, part of which does not ferment. A mash at 68-69 °C gives a rounder beer, with more body.

In between, 65 to 67 °C is the compromise of most recipes.

Temperature and time

• A single 60-minute rest between 64 and 68 °C is enough for the vast majority of beers with today's malts.
• Conversion is often complete in 30 to 45 minutes; the full hour leaves a margin, especially in a thick or slightly cool mash.
• A final 10-minute rest at 76-78 °C (mash out) stops the enzymes and makes the wort runnier for lautering. It is useful in three-vessel and all-in-one setups, less so in BIAB.
• The iodine test checks conversion: a drop of grain-free mash on a white plate, a drop of iodine tincture. If the colour stays brown-yellow, the starch is converted; if it turns blue-black, keep going.

The water ratio

You usually mash with 2.5 to 3.5 litres of water per kilo of grain when you sparge afterwards, and with all the water for the batch (5 to 7 litres per kilo) when you do not. A thick mash protects the enzymes better and converts a little faster; a thin mash lauters more easily. Both work.

The ratio changes the temperature of the water to heat: the more water there is, the less the cold grain lowers the temperature. To hit 66 °C with 5 kg of grain at 20 °C, the water must be heated to 72.3 °C with 15 litres, but only to 69 °C with 30 litres. The strike water temperature calculator does the sum for your quantities, and the mash temperature correction tells you what water to add if you are off.

Single infusion or step mash

• Single infusion: a single rest around 66 °C, possibly followed by the mash out. This is the most common.
• Successive steps: for example 62 °C for fermentability, then 72 °C for body, then 78 °C. They need a vessel that heats (BIAB on the stove, all-in-one system, RIMS or HERMS) or additions of boiling water.
• The protein rest (50 to 55 °C) is only useful with poorly modified malts or a lot of wheat and oats; with modern base malts, it can reduce head retention.
• Decoction: you draw off a thick part of the mash, boil it and return it to reach the next step. It is the traditional method of Czech and German lagers; the decoction volume calculator gives the amount to draw off.

pH

The enzymes work best when the mash is between 5.2 and 5.6 pH, measured at room temperature. With average tap water and a pale recipe, you often get there without doing anything; very hard water or a very pale beer may need a little acid. The tools in the Water theme help you predict it.

In BIAB

All the water is in the pot, the grain in the bag. The mash is very thin, the heating temperature close to the target, and conversion goes well. To hold the temperature for an hour, insulate the pot (blanket, insulating jacket) or briefly relight the heat while stirring, with the bag lifted off the bottom. Steps are easy to do by heating gently, always stirring. See the BIAB guide.

In an all-in-one system

The controller holds the steps and the recirculation evens out the temperature: it is the simplest setup for successive steps. Program a rise of about 1 °C per minute between two steps. The displayed temperature is measured under the malt pipe: check with a thermometer in the middle of the grain during your first batches. See the all-in-one system guide.

In three vessels

In a cooler, the temperature does not come back up: get it right from the start, after preheating the cooler. An extra step is done by adding boiling water (step infusion) or by decoction, or with a RIMS or a HERMS. See the two or three vessels guide.

With malt extract

Extract has already been mashed. Specialty malts (crystal, roasted) are simply steeped for 30 minutes between 65 and 70 °C, with no need for conversion. Only base malts (pilsner, pale ale, munich) need a real mash: this is the partial mash, described in the malt extract guide.