Author: Marshall Schott

Arguably, the single most important component of brewing, responsible for converting the boring starches in a kernel of grain into amazingly sweet fermentable wort, is the mash. Without it, we couldn’t make the immensely delicious beers we make today. As every all grain brewer is very well aware, there are many variables to consider when deciding how to approach mashing a particular beer, nearly all focusing in one way or another on the variable of temperature. Real scientists have long since understood and spread their knowledge of how mash temperature impacts the resultant wort and finished beer, and since I’ve no interest in pretending to be as smart as them, I won’t go into too much detail (geek-out here, here, and here).

For the purposes of this xBmt, my focus will remain solely on single infusion mashing, characterized by steeping milled grain at a single temperature for a given amount of time. During this so-called saccharification rest, the starches are converted to fermentable sugars by 2 main enzymes, here’s a dumbed-down version how they work:

Beta-amylase is said to be most active between about 131°F-150°F (55°C-66°C) and chops up whatever the hell gets in its way into smaller bits of mostly maltose, a highly fermentable sugar. Because of this, lower mash temps have been shown to produce more fermentable worts.

Alpha-amylase is quite different in that it is more active at warmer temps ranging from about 154°F-162°F (68°C-72°C), converting starches into maltose as well less fermentable sugars and unfermentable dextrins.

In essence, a lower mash temp purportedly produces a beer with a lower FG that’s dry with a thinner body and crisp mouthfeel, while a beer mashed warmer is said to finish with a higher SG and be sweeter with a fuller body. Obviously, there’s far more to mashing than this, but that’s not really what I’m hear to discuss, rather I’m curious about the impact mash temperature has on perceptible differences.

| PURPOSE |

To evaluate the impact mash temperature has on 2 beers of the same recipe mashed at drastically different temperatures– 147°F and 161°F.

| METHODS |

Thanks to HomeBrewSupply.com for providing the recipe kits used for this xBmt. During chats with the guys from HBS, they were a bit surprised to learn I’d never brewed Biermuncher’s Centennial Blonde Ale, which sits in the #1 position on HomebrewTalk’s Top 10 Recipes list. The kits arrived well packaged with all of the ingredients marked, making them easily identifiable, and the 2 packs of Wyeast 1056 American Ale yeast were wrapped with ice packs.

My first order of business was making a yeast starter a couple days prior to brewing, I pitched both smack packs into a single 2 liter flask with plans to split it between each fermentor after harvesting some for future use.

I milled the grain and collected the full volume of water for both no sparge batches the night prior to brewing. I awoke the following morning and began to heat both kettles of water to strike temp, which took about 5 minutes longer for the high mash temp batch. To keep things from getting too confusing, I still staggered the start of each batch by about 10 minutes.

While I’d considered comparing a simple 10°F difference in mash temp, I ended up changing my mind and settling on the more extreme ends of the single-infusion mash range.

Each mash was allowed a 1 hour saccharification rest before the sweet wort was collected and transferred to kettles.

This is where I noticed the first rather obvious difference between the batches, with the high mash temp wort developing a rather large and persistent layer of foam.

Even as the wort was boiling, the foam stuck around, making be wonder if this was an indication of how the finished beers might differ in terms of head retention.

Hops were added at the appropriate times throughout the boil then the wort was chilled and racked to 6 gallon PET carboys. A post-boil OG comparison confirmed my process was pretty consistent between the batches.

Both fermentors were placed in my temp controlled chamber and allowed to finish chilling to my target fermentation temperature, it took about 2 hours to reach 66°F, at which point I pitched the yeast. Signs of activity were present in both just 12 hours later.

I began to notice some differences in appearance at the 18 hour mark, with the kräusen on the high mash temp beer staying fairly low with larger bubbles while the low mash temp kräusen was beginning to grow.

Sure enough, the low mash temp batch ended up making a mess 24 hours into active fermentation.

I swapped the airlock with a blowoff rig and left it on until the kräusen dropped a bit, maybe 8 hours or so. The high mash temp beer was tame throughout fermentation.

I took the first hydrometer measurement once signs of fermentation activity had waned, then confirmed it hadn’t changed the following day, 6 since brewing the beer.

The .009 SG difference was initially pretty shocking to me though ultimately left me feeling confident such a highly discussed process component actually did what it’s purported to do– science works! I proceeded to cold crash, fine with gelatin, and package in kegs.

To carbonate, I hit each keg with 40 psi for 18 hours before purging and reducing to 13 psi for serving. By the time I began to collect data the following weekend, both beers were carbonated and looking nice.

| RESULTS |

A total of 20 people participated in this xBmt including many BJCP judges, obsessed homebrewers, and certifiable craft beer nerds. A discriminative sensory analysis method referred to as a triangle test was used to determine distinguishability and involved each participant being served 3 samples in different colored paper cups, 2 from the low mash temp batch and 1 from the high mash temp batch, then asked to select the different beer. In order to reach statistical significance given the sample size, 11 participants (p<0.05) would have had to accurately select the high mash temp sample, though only 9 (p=0.134) were capable of doing so, implying a general inability for people to reliably distinguish between a beer mashed at 147°F from another mashed at 161°F.

The 9 participants who made the correct selection on the triangle test were asked to complete an evaluation comparing only the 2 different beers, though they remained blind to the nature of the xBmt. It’s important to interpret the following information with caution, as the failure to achieve statistical significance means those who completed this evaluation may have done so by chance. Also, responses were all over the board on this one…

Four tasters perceived the aroma between the beers as being similar while 3 thought they smelled exactly the same and 2 felt they were not at all similar. Of those who reported noticing a difference, 5 preferred the aroma of the high mash temp beer and 1 liked the low mash temp beer more. Regarding flavor, 6 of the 9 tasters experienced the beers as tasting somewhat similar, 2 said they were not at all similar, and 1 thought they were exactly the same. Things get a little more interesting when it comes to mouthfeel, as not a single taster perceived the different samples to be exactly the same, with 6 saying they were somewhat similar and 3 believing they weren’t at all similar. A pretty striking majority of 7 tasters reported preferring the mouthfeel of the high mash temp beer compare to only 2 who liked the low mash temp beer’s mouthfeel better. Overall preference was split with 5 and 4 tasters expressing preference for the low mash temp beer and high mash temp beer, respectively.

At this point, the nature of the xBmt was revealed to the 9 tasters and they were then asked to select the one they believed was mashed warmer. Only 4 chose the correct sample.

My Impressions: I want to send a hearty cheers to Kevin “BierMuncher” Mattie for designing such an easy-drinking and flavorful beer! This was perfect to have around for the last couple weeks of summer, which is about as long as it lasted, as everyone who came over while it was on tap couldn’t keep their hands off. Regarding my experiences trying to distinguish between these beers, and even with my obvious bias, I honestly could not tell them apart. As is often the case, I was almost convinced I could detect some very slight differences when I first started pulling pints for myself, but this feather of confidence quickly drifted away as I began to attempt triangle tests served to me by others. At the very least, I expected to perceive a fuller body in the high mash temp beer, but side by side, it was essentially impossible for me to tell them apart.

| DISCUSSION|

I reckon every all grain brewer is at least somewhat aware of the impact mash temperature has on wort, most particularly that lower temps increase fermentability while higher temps decrease it. The objectively observable differences between the beers in this xBmt corroborate this scientifically valid fact– the higher beta amylase activity in the low mash temp beer resulted in a FG of 1.005 while the increased alpha amylase activity in the high mash temp sample resulted in a FG of 1.014, a strikingly vast .009 SG difference. Prior to this xBmt, if asked how 2 beers of such varying FG might differ, I would have thoughtlessly, perhaps even arrogantly, claimed the differences in body and especially perceived sweetness would be easily identifiable. It’s a line of reasoning that, on the surface, seems obvious: higher FG = more sugar = sweeter. The data just doesn’t seem to back this up, which I find incredibly surprising.

On a more anecdotal level, many of us have enjoyed commercial beers mashed on the warmer end of the spectrum that aren’t known for being cloying such as Lagunitas IPA, which is purportedly mashed at 160°F and finishes around 1.018 FG. Perhaps there’s more to this story, shit we thought we understood that we could learn more about. While I’ve no good way of measuring it, I’m curious if the types of dextrins remaining in a beer that was mashed on the warmer end of the spectrum are imperceptible to the human palate. This obviously doesn’t explain the fact mouthfeel between the beers wasn’t a dead giveaway, something that continues to stump me.

Finally, I’ve yet to comment on another aspect of this xBmt that didn’t seem to have an impact on the ability for tasters to tell a difference between these beers– level of alcohol. The low mash temp beer had a calculated 4.4% ABV while the high mash temp beer clocked in at a much lower 3.4% ABV. Whoa. Perhaps higher mash temps are just the ticket for those who prefer making flavorful examples of big beers with lower amounts of alcohol– Session Imperial Stout, anyone?

If you have any thoughts on this xBmt, please share them in the comments section below!

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