Mash Temp Rising: Analyzing The Results From Past exBEERiments On Mash Temperature

Author: Marshall Schott

Mash temperature has long been one of the more hotly debated variables in brewing, with many brewers speaking confidently about the impact just 2°F/1°C will have on beer character. Who hasn’t received feedback to lower the mash temperature a bit to encourage attenuation and thus reduce sweetness, or to increase the mash temperature to improve body and mouthfeel? For all-grain brewers, this idea feels like common sense, in part because we’ve heard and read about it since the dawn of the mash tun, but also because the objective measurements we take prove that mash temperature has an effect on residual sugar content.

Like pretty much every brewer I know, I was wholly convinced there was a strong correlation between mash temperature and sweetness, which heavily influenced the way I design recipes. But was my conviction about the impact alpha and beta amylase activity has on the perceptible qualities of beer as accurate as I’d been led to believe?

Over the years, we’ve run 7 exBEERiments focused specifically on the impact of mash temperature, doing our best to keep the conditions as controlled as possible, and making sure to provide some objective data alongside our standard sensory analysis findings. I’ve done my best to summarize those results in hopes of eliciting information that’s at least somewhat more meaningful than “because that’s what Dr. Beer said,” while also shining a light on the things we got both right and potentially wrong.

| Framework |

As a reminder, we rely on the triangle test, which involves serving two identical samples of beer and one different sample of beer to tasters who are blind to the variable, then asking them to identify the unique sample. Using a binomial proportions test, statistical significance is reached when the p-value is lower than 0.05, which indicates that a certain number more tasters than would be expected by random guessing were able to identify the odd-beer-out. A p-value higher than 0.05 suggests the variable did not produce a perceptibly different beer, not that the variable in question doesn’t have an impact. This matters because we’re not asking if a variable leads to a measurable difference; rather, we’re asking the more practically important question, “Can regular beer drinkers perceive a difference?”

| exBEERiments |

In all of the following xBmts, identical recipes were used to brew 2 batches of beer with all process variables held constant except for mash temperature. What follows are brief overviews of several past mash temperature xBmts including participant count, the number of correct responses that were expected in order to achieve significance, the number of actual correct responses, and the p-value.

Czech Pale Lager: 149°F/65°C vs. 153°F/67°C

The results of that first mash temperature xBmt led to quite the discussion among the Brülosophy contributors, as we all held the same belief about its impact. At one point, Ray Found posited that perhaps the differences would be more noticeable if the between-batch temperature delta was less vast, so he designed a follow-up xBmt comparing Czech Pale Lagers mashed at either 149°F/65°C or 153°F/67°C.

Participants: 25
Expected: 13
Actual: 6
p-value: 0.88 – not significant

Likely due to the difference in mash temperature being relatively minimal, fermentation stats weren’t as dramatic, though the beer mashed cooler did attenuate slightly more. Out of the 3 semi-blind triangle tests Ray attempted, he picked the odd-beer-out just once, and that was admittedly a guess. Looking back on this a decade later, the results feel less surprising given the smaller difference in mash temperature, but it added to the pile of data nonetheless.

Munich Helles: 147°F/64°C vs. 164°F/73°C

Contributor Jake Huolihan readdressed this variable again in 2018, opting to mash one batch of Munich Helles at 147°F/64°C and the other at 164°F/73°C, for a whopping 17°F/9°C difference. At this point, given the results of the prior xBmts, he was interested in testing the extreme, and he served it to an even larger group of participants.

Participants: 33
Expected: 17
Actual: 12
p-value: 0.42 – not significant

Interestingly, the beer mashed cooler started at 1.045 OG and finished at 1.003 FG (93.3% attenuation) while the one mashed warmer started at 1.049 OG and finished at 1.023 FG (53.1% attenuation). This resulted in a difference of 2.1% ABV, all driven by mash temperature. While Jake only got 3 of his 5 semi-blind triangle tests correct, he initially thought he perceived the high mash temperature beer as having slightly more malt flavor, not sweetness.

Belgian Golden Strong Ale: 148°F/64°C vs. 164°/73°C

Fascinated and confounded by the aforementioned results, contributor Matt Del Fiacco suggested that perhaps the effect of mash temperature would be more noticeable in a stronger beer with a higher concentration of sugars. He’d also heard that more characterful yeasts react differently to short- and long-chain sugars, so for his xBmt, he compared Belgian Golden Strong Ales mashed at either 148°F/64°C or 164°/73°C.

Participants: 23
Expected: 12
Actual: 10
p-value: 0.21 – not significant

Similar to Jake’s Munich Helles xBmt, the beer mashed cool started at a slightly lower 1.078 OG and finished at 1.014 FG (82.1% attenuation) while the beer mashed warm started at 1.081 OG and finished at 1.020 FG (75.3% attenuation); this resulted a smaller 0.3% ABV difference. Also like Jake, Matt identified the unique sample in just 3 of his 5 semi-blind triangle tests and he, too, felt there were no notable differences in sweetness, body, or mouthfeel.

English Porter: 147°F/64°C vs. 163°F/73°C

During the height of the COVID pandemic, contributor Andy Carter recognized that all past mash temperature xBmts had focused on pale colored beers, so he designed a replication comparing a much darker English Porter mashed at 147°F/64°C to one mashed at 163°F/73°C. Since he wasn’t able to collect data from tasters due to caring about others enough to stay home, all of the data for this came from his series of semi-blind triangle tests.

Trials: 10
Expected: 7
Actual: 9
p-value: 0.0004 – significant

Wait, what?! While not perfect, Andy’s performance does seem to suggest that mash temperature did indeed have a perceptible impact, and he wondered if perhaps it was due to the more complex grain bill. Whereas the beer mashed cool started at 1.053 OG and finished at 1.012 FG (77.4% attenuation), the beer mashed warm started at 1.055 OG and finished at 1.025 FG (54.5% attenuation), for a 1.5% ABV difference. Not to minimize Andy’s tasting prowess, but it behooves us to acknowledge the fact he designed this xBmt and brewed the beers, making him quite biased. Still, a fascinating result.

German Pils: 147°F/64°C vs. 160°F/71°C

Admitting that both the findings, and lack of consistency, of the previously discussed mash temperature xBmts were difficult to swallow, contributor Jake Huolihan decided to test it out again on a German Pils mashed at either 147°F/64°C or 160°F/71°C. Like Andy, this was done during a period where COVID restrictions forced us to collect data on ourselves.

Trials: 10
Expected: 7
Actual: 5
p-value: 0.21 – not significant

Yet again, the beer mashed cooler started at a lower 1.049 OG and finished at 1.007 FG (85.7% attenuation) while the one mashed warmer started at 1.053 OG and finished at 1.021 FG (60.4% attenuation), for a difference of 1.3% ABV. This being his second xBmt on the same variable with the same non-significant result, Jake concluded that perhaps mash temperature is best used as a tool to modulate alcohol level rather than sweetness and mouthfeel.

Saison: 148°F/64°C vs. 164°F/73°C

Our most recent xBmt on this topic was performed by contributor Alex Shanks-Abel who wondered how mash temperature would affect a beer fermented with a diastaticus (STA1+) yeast strain. To test their hypothesis out, they compared Saisons fermented with Imperial Yeast B64 Napolean that were mashed at either 148°F/64°C or 164°F/73°C.

Participants: 21
Expected: 12
Actual: 14
p-value: 0.002 – significant

We got another one! Both beers started at 1.067 OG, presumably due to the STA1+ yeast, and the one mashed cool finished at 1.001 FG while the one mashed warm finished at 1.002 FG, leading to negligible differences in attenuation and ABV. What’s interesting is that Alex only got 1 of their 5 semi-blind triangle tests correct, and they admitted to not tasting a difference at all between the beers.

| CONCLUSION |

To clarify this in as succinct a way as possible, all of the xBmts we’ve performed on this variable have supported the well-established fact that attenuation is a function of mash temperature – cooler temperatures activate beta amylase, which results in short chain sugars that are more fermentable, while warmer mash temperatures activate alpha amylase that produce less fermentable long chain sugars. Rad – our findings are consistent with the “real” science.

Where it seems we’ve been led astray is the idea that mash temperature affects qualities like sweetness, body, and mouthfeel. I suspect this claim is rooted in the knowledge that FG is an indicator of residual sugars in beer, and the presumption that all sugars are perceptibly sweet. On a superficial level, it makes sense that this would be the case because, for the vast majority of our lives, sugar has been synonymous with sweet. What seems to have been left out of consideration is the fact the long chain dextrins in beer just aren’t perceptibly sweet.

Before anyone gets too bitter about me making grand claims based on garage science, there’s actually real data out there that corroborates what I’m saying. In one study, researchers found that dextrins at standard beer concentrations of 10-50 g/L were not perceived as sweet, and that shifts in viscosity only occurred at much higher concentrations (Ragot et al.; 1989). Another study concluded that perceived sweetness does not increase with the presence of non-fermentable dextrins or higher FG resulting from unfermentable extract (Langstaff, Guinard, and Lewis; 1991). Finally, a review of decades of research examining the chemicals responsible for beer palate fullness and taste attributes concluded that non-fermentable dextrins have little to no effect on sweetness or perceived body (Langstaff and Lewis; 1993).

When viewing our exBEERiment results and the “real” science together, it’s hard not to see it as dispelling the historical assumptions that high mash temperatures create sweeter or fuller beer through residual dextrins alone. Am I claiming that mAsH tEmPeRaTuRe DoEsN’t MaTtEr and suggesting people ignore it altogether? Nope, not at all. In fact, I couldn’t care less what another brewer chooses to do on their brew days. But personally, I’ve come to view mash temperature as a lever to control ABV, not sweetness, body, or mouthfeel. One example where this has come in handy for me is making session beers that don’t taste like watered down versions of their normal strength siblings – rather than reducing the amount of grains to achieve the lower OG, I’ll up the mash temperature to around 166˚F/74˚C, then make much smaller adjustments to the grain bill. More grains, more flavor, lower alcohol. And if I miss the precise mash temperature I was aiming for… oh well.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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