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Mashing is the brewing term for steeping malt and other grains in hot water in order to extract the starches from the grain and allow them to be converted into sugar. In all-grain brewing, the mash is where the wort is created.

Theoretical Background of Mashing

The Theory of Mashing 
This article provides an in depth explanation of the enzymatic processes during the mashing process. It explains in detail the starch conversion process as well was the protein degradation.
Understanding Mash pH 
pH is an important parameter for mashing. Though malt has the capability to correct the mash pH most of the times, this article explains how the mash pH is established and how it can be affected.
Mash temperatures 
A table that summarizes the different temperatures that may be of importance for the mashing process.

Which mash schedule to choose

This question comes up quite frequently in the form of "What benefit do I get from using a more complicated mash schedule than single temperature infusion?".

Mashing needs to be seen as an extension of the malting process and what wasn't done during the malting of the grain, needs to be done during mashing. And the more modified a malt is, the fewer mashing steps are necessary to produce a wort suitable for brewing a quality beer. Even worse, by selecting a more intense mashing schedule for a highly modified malt certain steps, like protein conversion, can be overdone and lead to a less optimal wort composition.

Here is a list of some malts showing mashing schedules that work well for them:

  • American or British 2-row (Pale malts): single infusion mash
  • Durst TurboPils: single infusion mash
  • Durst Pilsner: single infusion or 2 step infusion
  • Briess Pilsen: 2 step infusion / decoction mash
  • Weyermann Pilsner/Vienna/Munich: 2 step infusion
  • Home-malted malt: multi-step infusion / decoction mash

Mashing Procedures

Whether you choose a single or step mash, there are a number of ways to achieve your mash temperatures.

Infusion mashing

Infusion mashing is the process of achieving your mash temperatures by adding measured amounts of water heated to carefully calculated temperatures to the mash.

In a single infusion mash, the mash water is added all at once and the mash is held at a single steady temperature for the entire mash. In a step infusion mash, some of the water is held back and heated then be added to the main mash to raise the temperature to each additional step. In either case, an insulated mash tun, such as a converted picnic cooler mash tun, is used to keep the temperature steady without the need for direct heat.

Direct heat

Directly heating the mash to maintain or adjust temperature can result in scorching and cause compounds that add off flavors to the beer. Direct heat can also de-activate enzymes causing incomplete starch conversion in mashes with marginal diastatic power. A decoction can be used to raise the mash temperature.

Decoction Mashing

In decoction mashing the temperature of the mash is increased by removing a part of the mash, bringing it to a boil and returning it to the main mash. Decoction mashes are categorized by the number of decoctions that are pulled, boiled and returned: