Author: Malcolm Frazer

Through thousands of years of human ingenuity, we’ve learned how to form raw materials of nature into a consumable that tastes as good as it makes us feel. It’s pretty incredible to consider the path brewing and beer has taken to land where it has today, from the discovery of malting and mashing to the breeding of hops with specific desirable characteristics and the isolation of particular strains of yeast. All of this knowledge formed over years of experimentation that ultimately led to the formation of methods known to consistently produce a quality product.

Indeed, brewing is steeped in tradition, many of the methods developed as a means of accomplishing a specific goal due to limitations in ingredients, equipment, or even knowledge. One such method developed in the early days of organized brewing by German brewers is the decoction mash, which was initially intended to combat effects of lower modification of malts as well as a way to overcome limitations on temperature monitoring and control existing at the time.

Put simply, decoction mashing is a method for increasing the temperature of the mash in a series of steps that involves removing portions of the mash, boiling it, then returning it back to the main mash. In addition to increased efficiency with malts of lower modification, brewers began to rely on decoction mashing to impart what they believed to be unique character to their beer.

While some have written decoction off as a remnant of our less advanced brewing past, others continue to employ the time consuming procedure convinced it has a positive impact on their beer. Having performed many decoctions myself, I was excited to finally test this one out!

| PURPOSE |

To evaluate the differences between a German Pilsner made using a triple decoction method and a beer of the same recipe made with a single infusion mash.

| METHODS |

While deciding what style of beer to make for this xBmt, I tapped some lager brewing friends to see what they thought might best showcase the effects of a triple decoction. I received a few different suggestions and ultimately settled on German Pilsner, as I felt its simplicity would lead to less obfuscation of whatever impact the decoction process might have.

A Certain… Ich Weiß Nicht Was

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.6 gal 70 min 41.3 IBUs 3.8 SRM 1.052 1.017 4.6 % Actuals 1.052 1.009 5.6 % Fermentables Name Amount % Pilsner (2 Row) Ger 10.25 lbs 91.62 CARAHELL® 9 oz 5.03 Acid Malt 6 oz 3.35 Hops Name Amount Time Use Form Alpha % Saaz 42 g 70 min Boil Pellet 6.4 Hallertauer 14 g 60 min Boil Pellet 4.1 Hallertauer Hersbrucker 14 g 30 min Boil Pellet 2.3 Hallertauer Hersbrucker 28 g 5 min Boil Pellet 2.3 Yeast Name Lab Attenuation Temperature German Bock Lager -Slurry for 400 Billion (WLP833) White Labs 73% 48°F - 55°F Mash Step Temperature Time Dough-In/ Protein Rest 133°F 10 min Dextrinization Rest 148°F 30 min 2nd Saccharification Step 158°F 30 min Mash Out 171°F 10 min Notes Water Profile: Ca 70 | Mg 16 | Na 36 | SO4 111 | Cl 67 | HCO3 81 | pH 5.3

Fortunate enough to have friends in the brewing industry, I scored a massive pitch of WLP833 German Bock Lager yeast slurry from Helicon Brewing the morning of my brew day, thus starters were unnecessary. After gathering the liquor for both batches and adjusting their profiles with minerals, I weighed out and milled separate sets of the same grain with the help of my loyal brewing assistant, Mollie the Masher.

Since the decoction method involves a bit more physical and mental effort than my standard single infusion approach, I decided to get it going first. While some brewers opt for a lower temperature dough-in and acid rest, I decided to forgo this step to avoid any possible impact on pH caused by phytic acid. I relied on BeerSmith to determine the strike temperature required to hit the initial rest temperature of 133°F/55°C.

I referred to a modified version of the Hochkurz decoction method discussed by Kai Troester to determine the volumes of mash to remove for each decoction in order to hit each step temperature. This method involves drawing off slightly more thick mash than some calculators recommend, the added mass ensuring target rest temperatures are hit, then adding back only enough of the boiled mash to hit the target step temperature; any leftover mash either remains in the kettle until the next decoction or, assuming a long enough rest, can be added back to the main mash once the temperatures match.

Immediately after mashing in, I pulled off approximately 30% of the thick mash, placed it in another kettle, and brought it to a rolling boil. The main mash was left at protein rest for approximately 10 minutes.

The first decoction was boiled, then I added enough back to the main mash to achieve the second rest temperature of 148°F/64°C.

After another brief pause, I moved a similarly sized portion of thick mash to the decoction kettle, raised the temperature to a boil and boiled it for 15 minutes for a total of 30 minutes for this rest.

Adding this boiling mash back to the main mash brought the temperature up to 158˚F/70˚C, where it sat for 30 minutes.

It was around this point I mashed in on the single infusion batch to hit my target saccharification temperature. Easy mode!

While the single infusion was left alone for a 1 hour rest, I pulled a third and final decoction, boiled it for 15 minutes, then added it back to the main mash, which raised it to a mash-out temperature of 171˚F/77˚C.

Mash pH readings were taken for both batches along the way and were different, though not by as much as I might have assumed.

After collecting the first runnings from both batches, I noticed the decoction batch had slightly less volume than the infusion batch, likely due to evaporation during each decoction step. Having previously consulted with the crew regarding how to address this issue, we decided for this initial xBmt to use just enough extra water during the sparge to the decoction batch to bring it to the same pre-boil volume as the infusion batch, our reasoning being to ensure any differences weren’t due to evaporation but rather the boiling of the mash. I added a smidge over 1 liter of water to the decoction wort and proceeded to boil both for 70 minutes with hops added at the times listed in the recipe.

The worts were quickly chilled at the completion of the boil and I took hydrometer measurements showing a very small difference between the batches.

I pulled off a few ounces of each wort for a better color comparison at this point.

Two marked fermentors were then filled with the same volume of wort from each batch then I let them finish cooling to my target pitching temperature of 48˚F/9˚C.

Once the temperatures were stable, I pitched even amounts of fresh WLP833 German Bock Lager yeast slurry into each.

I then set both fermentors to maintain a fermentation temperature of 50˚F/10˚C and decided to employ a more traditional lager fermentation method– each batch was held at 50˚F/10˚C until they were within 0.004 SG of the expected FG, after which I raised the temperature of each fermentor to 54˚F/12˚C to encourage complete attentuation, leaving them until FG was reached and no off-flavors were detected. Judging by airlock activity, both beers started fermenting around the same time and appeared to continue with similar vigor throughout. The beers fermented 11 days at 50˚F/10˚C and 3 additional days at 54˚F/12˚C before I pulled hydrometer samples confirming FG had been reached.

At this point, I dumped the trub and chilled the beers in their fermentors down to 40˚F/4˚C where they lagered for 12 more days before I proceeded with kegging them under pressure.

The filled kegs were placed in my keezer and hit with 40 psi of CO2 overnight prior to being purged and set to serving pressure of 12 psi where they remained the following week. When it came time to collect data, the beers were both perfectly carbonated and clear.

| RESULTS |

A panel of 33 people with varying levels experience participated in this xBmt. Each blind taster was served 2 samples of the single infusion beer and 1 sample of the triple decoction beer in differently colored opaque cups then instructed to select the unique sample. At this sample size, 17 tasters (p<0.05) would have had to accurately select the unique sample to achieve statistical significance. Ultimately, 15 tasters (p=0.10) chose the different beer, suggesting participants were not able to reliably distinguish a German Pils made using a triple decoction method from the same beer made using a single infusion batch sparge method.

Some readers have questioned whether blindness to the xBmt variable may be the reason participants are unable to detect differences between the samples, that perhaps by knowing what the test is about, they’d be able to focus more on meaningful aspects of the beer and thus increase their odds of correctly choosing the unique sample in the triangle test. While it goes against accepted sensory analysis practices, to satiate the curious, we decided to analyze how “sightedness” effects performance and administered the triangle test to a group of 22 new participants after informing them of the variable; they were not made aware of which beer was the unique sample, just that two German Pilsners were made using either a triple decoction or single infusion. In order to reach statistical significance, 12 tasters (p<0.05) would have had to correctly identify the unique sample, though only 8 (p=0.46) were able to do so, which not only confirms the non-significant blind data, but suggests one’s ability to distinguish between the samples may not be heavily influenced by knowledge of the variable.

Given the non-significant results, any further data collected is meaningless, as the findings don’t support the notion that triple decoction made a statistically distinguishable difference. But given the variable in question, we thought it’d be interesting to share preference data of only those who were correct on the initial triangle test. Please interpret with caution. The participants who correctly selected the decoction sample as being unique in the triangle test were instructed to complete a brief preference survey comparing only the two different samples while still blind to the variable. Of the 15 blind tasters who were correct, 4 preferred the triple decoction beer, 7 reported preferring the single infusion beer, and 2 said they perceived a difference but had no specific preference. Interestingly, 2 of the correct tasters admitted to perceiving no difference between the beers, suggesting the possibility their correct selections were simply a lucky guesses. Out of the 8 correct sighted participants, 5 preferred the triple decoction beer, 2 preferred the single infusion beer, and 1 person said they perceived no difference.

Purely for the sake of curiosity, we combined the blind and sighted data for analysis. With a total of 55 participants, 25 correct responses (p<0.05) would be required to achieve statistical significance, though only 23 tasters (p=0.12) correctly identified the unique sample, again failing to support the hypothesis that triple decoction produces a noticeable difference compared to single infusion.

My Impressions: I began sampling these beers prior to collecting data and believed from early on there was little chance tasters would be able to tell them apart, despite the rather radically different mashing regimen. I was admittedly in disbelief. I perceived the decoction beer as possessing a slightly stronger malt character with a hint more sweetness compared to the single infusion sample, which appeared to maintain a touch more haze. The difference was so subtle that I’m convinced I wouldn’t have noticed them had I not been searching for them so intently. After a few more days in the keg, around the time data was collected, whatever differences were present before seemed to become more noticeable to me, as I went 5 for 5 on various versions of semi-bind triangle tests, albeit none of which I felt very confident about. I was genuinely surprised when I was correct the the first 2 times, though in subsequent attempts, I knew exactly what to look for and was able to reliably detect the decoction beer- mother’s (brewers’s) intuition.

| DISCUSSION |

I’ve utilized different decoction methods many times over the years with the belief it resulted in beer with a richer malt character that simply couldn’t be had by a single infusion mash. This belief was consistently confirmed by my experiences with the decocted beers I made, as I always perceived them as possessing the sought after character decoction is said to impart. Acknowledging that confirmation bias could be at play, though hesitant to accept what I perceived was all in my head, I approached this xBmt fully anticipating a significant finding. Then I started sampling the beers for myself and was blown away by how incredibly similar they were, to the point I would have been surprised if the results were significant. All of this left me with more questions than answers. Is it possible the lauded decoction character is more a function of concentrated wort than actual cooking of the mash? Would the decoction beer have tasted different if I’d used a notably undermodified base malt? Where the hell was the melanoidin flavors I’d sworn I tasted in previous decoction beers?

I’m constantly left amused by participants’ preference ratings, not just because it demonstrates that certain methods, even when they do result in a noticeable difference, may not produce the most desirable outcome for some. The fact significance was not reached in this xBmt could mean the preference ratings were simply random picks, though it’s also possible those who were correct actually did perceive a difference and the majority just happened to like the single infusion beer more. Either way, this data reminds me that “what I like” may not require the methods espoused by others, but those that I’ve found produce the most satisfactory results for me.

It should go without saying these xBmt results do not “prove” decoction has no perceptible impact on beer, despite the fact participants were unable to reliably distinguish a decocted German Pils from one made using a single infusion batch sparge method. Of course, it’s likely some will rely on these results to confirm an already held belief, which as unavoidable as this is, we strongly recommend against. Considering the shear number of respected brewers who utilize decoction methods, a single data point such as this certainly is nowhere near enough to invalidate the practice. This case is obviously not closed and our hope is that these findings motivate further exploration of this interesting traditional method.

If you have experience with decoction methods or thoughts on the matter, please share in the comments section below!

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