Mash Out! January 2019

Mash Out! is a column for all your brewing questions, be it technical or culture. Should I form a homebrew club in my area? Do I need to add tannins and acid to my traditional meads? Ben Morris will be answering all your burning brewing questions. To submit a question, email with “Mash Out!” in the subject title. 

Q: Who needs a mash-out anyway?

The science of mashing is worth a full length book, and if anyone has taken the time to read through all of the Malt book, you’ll find out that grains and mashing gets drier than roasted barley. Bad joke, but let me have this one. Reading up on Windisch–Kolbach units (or degrees Lintner) and the effect of temperature, acidity, moisture, malt age, and mash-ratio on conversion efficiency reads like something out of the darkest depths of university chemistry. Thankfully, for anyone who has read How to Brew or other brewing books, we can focus on the easier variables to control such as temperature. To understand mashing-out as a part of our overall mash, we have to step back and think about what we are trying to accomplish in mashing barley in the first place and what factors are at play.

Historically malted barley was of poor quality and had a much lower extract potential than modern malts. A lack of understanding of biology, poor equipment and lack of process controls meant that malts were darker, smoky, and had much lower diastatic power (amount of active enzymes) and extract potential than modern malts. To get a better yield, long mashes with a slow temperature ramp were used to maximize extract – and provide some acidity or protein in some cases but that’s another whole book. As indirect heating became widespread and malts could be dried more evenly and more lightly, the enzymatic potential of grains was better preserved leading to better starch conversion and subsequently drier beers – and the birth Pilsner.

With more enzymes present in the malt, conversion time for mashes is greatly reduced. For example, Munich(10) has a diastatic power of 70 °L, whereas German Pilsner is over 110°L, American 2-Row is around 140°L and American 6-Row can be over 160°L. Brewing an American Pale Ale with almost all 2-Row has twice the conversion power of a mash that is predominately Munich malt and can be done in, theoretically, half the time.

But what does diastatic power have to do with mashing-out? During the days of poor malts, a mash-out wasn’t required. The goal was to maximize the extraction of sugars from the grain and the longer the mash was kept inside the conversion temperature range the better. Better converting grains mean less malt is required for the mash and brewers can simply add a bit of a darker malt for colour and flavour, rather than using a lot of a medium malt. In England this can be seen in the switch away from using Brown malt for Porters and instead using Pale malt with some Black Patent malt to colour it.

However there is a problem – the enzymes in paler malts will convert the starches in the darker malts and result in a dark, but dry beer. Anyone who has made a black lager or black IPA knows that colour isn’t an indicator of body – even Guinness is moderately dry at 1.009 FG – and so we have to stop the conversion of starches.

Imagine a simple infusion mash of 100% pale malt at 67c for 60 minutes. At the end of 60 minutes most of our starches should have been converted to fermentable sugars. If we begin lautering and sparging right away our mash will remain at the conversion temperature and slowly rise towards our sparge water temperature. Until the mash hits around 76c, roughly the temperature where malt enzymes are denatured, we are going to see additional conversion both in the mash tun and in the kettle. The length of the transfer is now tacked on to the mash length and the result will be a drier beer.  However, if we quickly heat the mash to above 76c and hold it for a few minutes we can largely denature the enzymes present in the grains and stop the conversion of starches to sugars, preserving the longer chain sugars present in our wort and therefore, the body of our final beer.

Depending on what you are brewing, mashing-out isn’t a required step – in fact some breweries employ a mash regime that calls for a 15 minute conversion rest at 65 or 67, and then they immediately begin transferring. The runnings are kept at conversion temperature for 60 to 90 minutes and then boiled. The result is wort that has a slightly lower efficiency than a 60-90 minute infusion mash, but takes over an hour less time. While this might not be necessary or ideal for home-brewers, and many might not have the process controls to do it well, on a large scale setup this can save a large amount of valuable time and greatly increase brewhouse output.

For the homebrewer a mash out will greatly help maintain body in your beers and can greatly help improve consistency from batch to batch. By denaturing the mash enzymes you can avoid additional conversion during lautering and in the kettle pre-boil helping to keep your beer from ending up ‘watery.’

For a good breakdown of the enzymes at play in your mash the WikiBooks article below does a good job of breaking everything down into discrete temperature ranges.

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