Author: Jake Huolihan

Out of all of the interesting xBmt results observed over the years, those exploring the impact of mash temperature have been some of the most shocking, at least for me. Despite producing clearly observable differences in FG, tasters have been unable to reliably distinguish beers mashed at disparate temperatures, calling into question claims that mash temperature can be used to adjust body and mouthfeel.

The reason for the FG differences based on mash temperature can be explained by the activity of alpha and beta amylase, the former of which is active at warmer temperatures and produces a less fermentable wort while the latter prefers cooler temperatures and creates a more fermentable wort. The ostensible belief held by many is that warmer mash temperatures lead to sweeter beer with thicker mouthfeel, which makes sense on the surface seeing as more long chain sugars remain.

Admittedly influenced by earlier xBmts on the topic, I’ve all but accepted that mash temperature has minimal impact on the perceptible qualities of beer. However, I continue to regularly witness brewers offering advice to make mash temperature adjustments for the purposes of body and mouthfeel characteristics. Curious to see what I might be missing, and in the spirit of good science, I designed a replication xBmt to test the extremes out for myself!

| METHODS |

For this comparison I whipped up a simple Helles in hopes of any differences being easily recognizable.

Oberteig

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 21.4 IBUs 3.7 SRM 1.045 1.008 5.0 % Actuals 1.045 1.008 4.9 % Fermentables Name Amount % Odyssey Pilsner 9.75 lbs 89.66 Weyermann Vienna 1.125 lbs 10.34 Hops Name Amount Time Use Form Alpha % Loral 5 g 60 min Boil Pellet 10.3 Loral 13 g 30 min Boil Pellet 10.3 Loral 5 g 5 min Boil Pellet 10.3 Yeast Name Lab Attenuation Temperature Global (L13) Imperial Yeast 75% 46°F - 56°F Notes Water Profile: Ca 65 | Mg 0 | Na 8 | SO4 67 | Cl 68 Download Download this recipe's BeerXML file

I whipped up a large starter of Imperial Yeast L13 Global a couple days ahead of time.

The night before brewing, I collected my water and adjusted it to my desired profile.

The next morning, I turned on the elements to heat my brewing water then proceeded to mill both identical sets of grain, which I’d measured out the night before.

While waiting for the water to reach strike temperature, I weighed out the kettle hop additions.

Since this variable would require dual mashes, I mashed in on the low mash temperature batch 30 minutes before the high mash temperature batch, treating them identically otherwise. Once the grains were fully incorporated into each mash, I checked to ensure I hit my target temperatures.

The mashes were left to rest for 60 minutes apiece, each on receiving a gentle stir every 15 minutes.

With the mashes complete, I lautered into separate boil kettles.

The elements were cranked up to heat the wort and each batch was boiled for 60 minutes with hops added at the times stated in the recipe.

During the boil, I noticed the high mash temperature batch had more foam than the low mash temperature wort. When the boils were finished, I quickly chilled the wort.

Refractometer readings revealed the low mash temperature wort was at 11.3° P (1.045 OG) while the high mash temperature wort was at 12.1° P (1.049 OG). Interesting…

Equal amounts of wort from each batch were racked to separate sanitized Brew Buckets.

The fermentors were placed next to each other in my fermentation chamber and allowed to finish to 50°F/10°C. Once there, I pitched identical amounts of decanted yeast starter into each batch before giving them 90 second doses of pure oxygen. Both batches were fermenting happily the next morning and were left alone for 14 days before activity had come to a halt. Hydrometer measurements confirmed previous findings that mash temperature has a rather drastic impact on attenuation.

The beers were transferred to CO2 purged kegs then placed in my cool keezer.

After 8 weeks of lagering on gas, the beers were clear, carbonated, and ready to be served to participants!

| RESULTS |

A total of 33 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the low mash temperature beer and 1 sample of the high mash temperature beer in different colored opaque cups then asked to identify the one that was unique. Given this sample size, 17 tasters (p<0.05) would have had to correctly identify the unique sample in order to reach statistical significance. In the end, only 12 tasters (p=0.42) made the correct selection, indicating participants in this xBmt were unable to reliably distinguish a Helles mashed at 147°F/64°C from one mashed at 164°/73°C.

My Impressions: I attempted 5 semi-blind triangle tests and accurately selected the odd-beer-out 3 times. Not a slam dunk, but I seemed to perceive the high mash temperature beer as having an ever so slightly stronger flavor of Pils malt. Obviously not enough for me to consistently identify it, so it’s possible my bias was at play. Despite their difference in ABV, the beers tasted nearly identical, which was a good thing seeing as I thought they were particularly tasty!

| DISCUSSION |

Mash temperature is viewed by many as a lever one can use to adjust how sweet or dry a beer is, a belief unquestionably informed by the easily observable relationship between mash temperature and attenuation. Who hasn’t received feedback from a judge or fellow brewer to reduce mash temperature because they felt the beer was too sweet? It seems only logical that stark differences in FG would be perceived in such a manner, which is why tasters’ inability to tell apart beers mashed at either 147°F/64°C or 164°/73°C in this xBmt is so shocking– the beers finished 16 SG points apart from each other!

Without question, the beers in this xBmt were different– the cool mash temperature beer was 4.9% ABV while the high mash temperature beer was 3.3% percent. Based on established brewing science, we can assert that the beer mashed warmer contained more long chain sugars thus leading to a lower fermentability. What’s so striking is that neither the differences in alcohol nor sugar content led to perceptible differences in the finished beers.

Interestingly, in De Clerck’s A Textbook Of Brewing Vol. 1, an experiment is discussed that found differences in dextrin level as a function of mash temperature did not produce perceptible differences in mouthfeel or flavor. This along with our xBmt results seems to suggest that mash temperature, with its impact on FG and ABV, may not be as useful of a lever for adjusting beer character as we’ve been led to believe.

As for me and my brewing, I’ll continue to mash most of my beers between 152°F/67°C and 154°F/68°C, as it seems optimal for balancing conversion and yield. I’m really curious about the various methods used to increase the sensation of fullness in beer and look forward to exploring it more in the future.

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

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