When brewing an all-grain beer, you need to decide on a mash method. If you are following a recipe, the mash details are likely spelled out for you. However, if you’ve drawn up your own recipe — or are using an existing recipe and want to pick the best mash method for it — you should know how to choose a mash method.
Many homebrewers will choose their mash method based on the style of beer they are brewing — a single infusion mash for an English ale, a decoction mash for a German lager, or one of the slew of different mash methods used in traditional Belgian brewing for brewing a Belgian beer. (You will also need to decide on a lautering method — of which continuous sparging, batch sparging, and the no-sparge, brew-in-a-bag (BIAB) method are three popular choices for homebrewers. But that’s another topic.)
Practical homebrewers should understand that mashing is an extension of malting and the vast majority of malts produced today are intended to be single infusion mashed. These malts are called fully-modified. Unless your malt is labelled otherwise, any base malt you buy is overwhelmingly likely to be fully modified.
Single Infusion Mashing
Most decoction or other step mashes have rests designed to degrade gums or proteins. In modern fully-modified malt, the grains are malted such that single infusion mashing will yield wort with an acceptable level of gums and proteins (and anything else you would change in a step mash). Putting a fully-modified malt through a step mash with a beta-glucan rest (or what used to be called a protein rest) is at best a waste of time and at worst it could have negative effects on your beer. For example, even fairly short rests (15 minutes) in the protein rest range can lead to less foam. As such, unless you have a good reason to do so, choose a single infusion mash as your mash method. It is likely to be your best choice.
If you know for certain that your malt has excessive gums or proteins, then a step mash may be just the thing. However, don’t perform a multi-step mash simply because you can do it. In most cases with fully-modified malt, a more complex mash schedule will not yield a better beer. Everything you would want to accomplish in that mash will have been done by the maltster. It can be fun to try traditional mash methods (decoction mashes, turbid mashes, etc.), but the malt you use will not be the same as the malt brewers historically used and won’t yield the same results.
If you want to brew something using a traditional method, go ahead, even if you are using a fully-modified malt. The beer will likely turn out fine (although perhaps not as good as it could have been). But be aware that — without the appropriate malt — you will not actually be fully mimicking the old school method.
When performing a single infusion mash, you have the option of mashing out. For a mash out, the brewer raises the temperature of the mash to 168–170 °F (76–77 °C) to decrease the viscosity of the mash, which leads to easier lautering and perhaps higher yields. This step can be skipped without causing too many problems, and indeed many homebrewers do omit it. However, if you expect lautering problems, are shooting for high extract efficiency, or trying to limit the fermentability of your wort (to make a sweeter, more full bodied beer), it’s best to mash out. Mashing out hastens the denaturation of the amylase enzymes and keeps them from continuing to work on the remaining carbohydrates in the mash.
When brewing with fully-modified malt, there is one case in which a step mash will help you — when brewing a dry beer. To make a highly fermentable wort, which will yield a dry beer, mash in at 140–145 °F (60–63 °C) and rest there before heating the mash into the low end of the regular single infusion mash range. The full range is often stated as 148–162 °F (64–72 °C), so ramping from the low temperature rest to 148–152 °F (64–67 °C) works well. (I like ramping up to 152 °F/67 °C, but that’s just a personal preference.)
You can hold the lower rest for up to a couple hours for a very dry beer, although 15 minutes should do it for a moderately dry beer. You can hold the higher rest so that the full mash time equals at least 60 minutes. The low temperature [140–145 °F (60–63 °C)] rest should not have any negative impact on your beer.
By The Numbers
A single infusion mash is usually carried out at 148–162 °F (64–72 °C). The lower end of the temperature range yields a more fermentable wort, suitable for brewing a fairly dry beer, while the higher end results in less fermentable wort, which results in a sweeter beer. Temperature is the variable that influences fermentability the most.
The mash thickness of a single infusion mash typically varies from 1.0–2.4 qt. of brewing liquor per pound of malt (2.0–5.0 L/kg), and the pH hopefully falls somewhere in the 5.2–5.6 range. (If it doesn’t, you should adjust the mineral content of your brewing liquor.) Thinner mashes, within the given range, produce slightly more fermentable worts.
Infusion mashes are frequently held for 60 minutes, especially at the homebrew scale. However, for sweet beers, you should perform an iodine test periodically and mash out immediately after getting a negative result. In contrast, if you want to brew a dry beer, extending the mash time (in the low end of the temperature range) will give the enzymes more time to work. For a “regular,” full-bodied beer, 45–60 minutes mash time will work well.
If you’re trying to brew a sweet beer, a mash out will help. It will also help if you are shooting for high extract efficiency. If you’re brewing a dry beer, you can skip the mash out and hold the wort in your kettle around 148–152 °F (64–67 °C) while you are collecting it to give the enzymes time to continue working. If you do mash out, and you use continuous sparging, your sparge water should be heated such that it holds the grain bed at 168–170 °F (76–77 °C).
With most modern, fully-modified malts, a single infusion is your best bet. This should be your default choice, and you should have to talk yourself out of it to switch to a step or decoction mash.
On Thursday, I will discuss when it is a smart move to employ a mash method other than a single infusion mash.