The Common Rests
When brewers design a mash schedule, they think in terms of “rests,” scheduled stops at specific temperatures. Each rest favors certain enzymes for a desired effect.
Dough In — A catchall term for the first step in your mash schedule.
Acid Rest — A low-temperature mash rest that promotes the mash acidification by creating phytic acid. Typical temperature: 90°F to 100°F for thirty minutes.
Protein Rest — The first rest for many Belgian and German beers. Favors the activity of the proteolytic enzymes. Typical temperature: 120°F to 128°F for twenty to thirty minutes.
Beta “Intermediate” Rest — The beta amylase rest favors maltose production. Used when you want a beer to dry out. Typical temperature: 145°F to 149°F for thirty minutes.
Saccharification Rest — The main starch conversion rest. Above 148°F, starch is completely dissolved in the mash liquor. The lower 150s produce balanced wort favoring neither dextrinous wort nor dry wort. Resting at 154°F to 157°F, the mash creates thicker dextrinous wort resulting in rich and sweet beer. Typical temperature: 150°F to 157°F for thirty to sixty minutes.
Mash Out — Heating to mash-out temperatures, in theory, denatures and stops enzymatic activity, freezing the sugar ratio. Some debate the effectiveness of the step. But as the mash heats up, it becomes looser, helping the lautering process. Typical temperature: 165°F to 170°F for ten to fifteen minutes.
Do I have to use all of these rests to make great beer?
Most beer these days is brewed with highly modified malt, eliminating the acid and protein rests (although brewers using unmalted wheat often use a protein rest). A number of micro and pub breweries have systems only capable of single-infusion mashes, so all you need is a saccharification rest. Some professional breweries even shorten their mash times to as little as twenty to thirty minutes before sparging.
The all-grain recipes here use a standard mash ratio of 1.25 quarts of water per pound of malt (for example, for ten pounds of malt in the mash, use 12.5 quarts [3.12 gallons] water in the mash). This standard mash thickness protects the enzymes and favors faster conversion. Mashing with less water yields a thicker mash that converts faster, but produces less fermentable wort. Thinner mashes work more slowly, but smaller sugars comprise more of the final wort.
There are a number of ways to heat your mash. For any direct heat method, including decoction, you must stir the mash continuously to prevent scorching the sticky mash. Scorched mashes ruin the beer!
Infusion — The simplest method, water infusion is the basis for mashing. When you heat water for the dough in, you're performing an infusion. Calculating the amount of water and temperature of that water to hit a target temperature can be incredibly tricky, but the rule of thumb for dough in is to use 1.25 quarts of water per pound heated 12°F above your desired rest temperature. Other infusions use boiling water to minimize diluting the mash. See Appendix C to calculate infusions.
Direct Heating — Light the fire under the kettle and stir continuously. Check your progress every minute or so. When you're 4°F to 5°F under your target temperature, kill the heat, stir like crazy, and wait five minutes and check again. If you're too warm, add cold water or ice and stir to cool the mash.
Decoction — Back before thermometers, they boiled mash to raise temperatures. Pull one-fourth to one-third of the grain (only a little liquid) to a separate pot. Bring the mixture to a boil and stir for ten to fifteen minutes. Add the boiling mash back to the main pot and stir to distribute. Use this to enhance maltiness.
Recirculation — The mad geniuses of homebrew take their copper immersion chiller and drop it into the HLT. They pump mash liquor through the now submerged coil. The sparge water heats the mash liquor before returning to the mash tun.
With any method other than recirculation, it is vital that you thoroughly stir the mash to eliminate hot pockets and evenly distribute the heat.
There are several traditional mash methods that vary in laboriousness. Each brewer comes to a place where they have a preference. Each of the mash profiles are listed step by step in Appendix D.
Single-infusion mashing — The simplest and most common mash profile. Infuse the malt into water to achieve a single mash temperature and hold for an hour. After an optional mash out, proceed with the sparge and the rest of your brew day. Most of the recipes in this book use this mash technique.
Multistep mashing — Slightly more complicated, the brewer targets multiple rest temperatures, adding heat to reach the next plateau. What temperatures are used depends upon the composition of the mash and desired beer characteristics. A Belgian brewer would perform a protein rest, followed by a beta rest to promote fermentability, and then a saccharification rest to finish conversion.
Decoction mashing — The old German technique for brewing that relies entirely on decoctions for moving between steps. Requires one, two, or three decoctions to get through the mash program.