Author: Marshall Schott

In his book Brewing Better Beer, the great Gordon Strong likens roasted grains (roasted barley, black patent, chocolate malt, etc.) to coffee, explaining the temperatures at which they’re roasted are high enough to denature any enzymes, meaning they do not need to be mashed. Not only is mashing roasted grains and malts unnecessary, but Strong adds it “can lead to harsher, more astringent flavors in the finished beer.” He does mention this is to some degree dependent on water chemistry, though concludes, “regardless, the dark grains are exposed to the most heat during this method, and that can lead to a harsher bitterness in the finished beer.” Strong goes on to discuss different methods for using roasted grains and malts such that these undesirable characters are avoided, one of which involves adding the roasted grains to the mash toward the end of the saccharification rest, a technique referred to by many as capping the mash. In the book, Strong suggests adding the milled roasted grains at mashout then performing a recirculated vorlauf, effectively treating them like coffee in a drip machine. Obviously written from the perspective of a fly sparge brewer not wanting to disturb the grain bed, many modern homebrewers have adapted this method for batch sparge, no sparge, and BIAB and report similar results by stirring the roasted grains into the mash during the last 10 or so minutes of the rest.

I was first inspired to try this capped mash method after my scoresheets for a Dry Stout competition contained the words “astringent” and “acrid.” To me, the subsequent batches were good, maybe even less astringent and acrid, so I adopted this method without much consideration, convinced it was improving the quality of my Brown Ale, Porter, and Stout.

Of course, bias may have (absolutely did) played a role in my perception, so when my desire for a low ABV roast-heavy beer began to creep up, I knew exactly which variable it’d be used to investigate!

| PURPOSE |

To evaluate the differences between a Stout where the roasted grains were included in the entire mash and one where the roasted grains were added in the last 10 minutes of the mash, during the vorlauf step.

| METHODS |

Curious how rye character might play with roasted grains and looking to get a bit more body than flaked barley usually imparts, I designed a simple Stout with a twist.

dRye Stout

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.3 gal 60 min 36.7 IBUs 36.0 SRM 1.039 1.008 4.1 % Actuals 1.039 1.011 3.7 % Fermentables Name Amount % Pale Malt, Maris Otter 5 lbs 58.82 Barley, Flaked 1.25 lbs 14.71 Rye Malt 1.25 lbs 14.71 Roasted Barley (Simpsons) 1 lbs 11.76 Hops Name Amount Time Use Form Alpha % Magnum 20 g 45 min Boil Pellet 11.2 Fuggles 30 g 10 min Boil Pellet 5.2 Miscs Name Amount Time Use Type Calcium Chloride 3.00 g 60 min Mash Water Agent Gypsum (Calcium Sulfate) 1.50 g 60 min Mash Water Agent Yeast Name Lab Attenuation Temperature San Diego Super Yeast (WLP090) White Labs 80% 65°F - 68°F

While a certain Irish strain of yeast is a popular choice for this style of beer, I wanted to see how one of my go-to yeasts would perform and built up a large starter of WLP090 San Diego Super Yeast a couple days before brewing.

Since I would be performing two separate mashes, which I staggered the start of by about 20 minutes, I went with the no sparge method and collected the full volume of brewing liquor for each 5 gallon batch.

As the water for the first batch was heating, I collected and milled the grains, holding back the roasted barley from the capped mash batch to crush on its own.

With the grain milled and water hot, it was time to mash in. Despite the 1 lbs difference in grain weight between the mashed and capped batches, the strike temp was very similar and both mash temps were consistent.

The hour-long saccharification rests commenced.

Approximately 15 minutes into each mash, I took pH readings and found my expectations were met. Wort from the batch with the roasted barley, known to increase mash acidity, was at a low 5.0 pH while the capped mash wort was at a perfect 5.3 pH.

About 15 minutes after collecting the sweet wort from the full mash batch, as it was coming to a boil, I “capped” the other mash with the roasted barley previously reserved and gave it a good stir.

After 10 minutes and 2 more brief stirs, I collected the sweet wort from the capped mash and brought it to a boil next to the already boiling full mash wort.

Both worts were boiled for 60 minutes, quickly chilled, racked to 6 gallon PET carboys, then placed in my temp controlled chamber where they sat for about 2 hours before reaching my target fermentation temperature of 66˚F/19˚C. The yeast was then equally split and pitched. I returned 18 hours later to find the beers fermenting as expected.

Besides the capped mash beer having a slightly paler kräusen, fermentation for both beers was observably similar. I took an initial FG measurement about a week after pitching the yeast, it matched the hydrometer reading 2 days later that showed the full mash beer had finished slightly higher than the capped mash batch.

The beers were then crashed for a couple of days then kegged and left to carbonate in my keezer for a few more days before being served to participants.

By data gathering time, both beers were looking awful nice, though their color was noticeably different.

| RESULTS |

A total of 22 BJCP judges, experienced homebrewers, and craft beer lovers participated in this xBmt. Each person was served 3 samples in different colored paper cups, 1 from the full mash batch and 2 from the capped mash batch, then asked to select the different beer. To reach statistical significance with this sample size, 11 participants (p<0.05) would have had to accurately select the full mash sample as being unique. Exactly 11 (p=0.049) made the correct selection, suggesting tasters were reliably able to distinguish between a beer made with roasted barley included in the full mash from one where the roasted barley was added during the last 10 minutes of the mash.

The 11 participants who made the correct selection on the triangle test were asked to complete a brief evaluation comparing only the 2 different beers, remaining blind to the nature of the xBmt. Overall 5 of the tasters preferred the full mash beer, 4 liked the capped mash beer more, and 2 had no particular preference. The independent variable was revealed and participants were offered an explanation as to how this technique is purported to impact the beer, then they were asked to select the sample they thought was produced using the capped mash method. A majority of 7 tasters accurately chose the cup containing the capped mash beer, while only 3 made the wrong selection. However, nearly all of those who made the proper selection said it had little do with astringency differences, which was not overtly noted by anyone, but rather the full mash beer was described as being “more flavorful, fuller flavor, less watery.” Interesting.

My Impressions: In 4 semi-blind triangle tests, I was able to accurately select the odd-beer-out three times, which meets my own private reliability standards. I experienced the full mash beer as being fuller in flavor and mouthfeel with a more rounded overall Stout character, while the capped mash beer actually came across to me as more astringent. Weird, I know, especially since I wasn’t the only one who experienced them this way. Curious what might be causing this perceived difference, I took a pH readings of the finished beers, fully expecting to see a difference similar to that observed when measuring the mash pH. I poured off small amounts of each beer and let them warm to 65˚F before proceeding.

Imagine my surprise when the full mash beer clocked in just .03 pH lower than the capped mash beer, within what I’d guess is a reasonable margin of error. Maybe this is to be expected, I’ve no clue and I’m nowhere near smart enough to understand how this happens, but at the very least it tells me any perceived differences likely weren’t a function of pH.

| DISCUSSION |

I trust (hope) I’m not the only one who feels uncomfortable settling on any conclusions based on a single point of data, particularly given the fact 1 response could have swayed the outcome. Either way, based on my biased experience and the results from this xBmt, I’m compelled to accept the capping the mash method may not necessarily have the impact I previously thought. Since I preferred the full mash beer, that’s what I’ll be sticking with for now, not because I think it’ll have some drastic impact on the quality of my beers, but mostly because it’s simpler. As with most of these xBmts, especially the first iterations, much more investigation is required in order to make any solid determinations, something I absolutely look forward to doing.

If you’ve messed around with different methods for using roasted grains, I’d love to hear what your experience has been like, please share in the comments section below!

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