exBEERiment | Impact Of A Single Decoction Mash When Using Under-Modified Malt In A Czech Pale Lager
Author: Jordan Folks
Beer production begins with creating wort through the mashing process, during which endemic enzymes are activated that convert starches into fermentable sugars. There are a number of factors at play when it comes to how much of these sugars are created during the mash including the specific approach to mashing, of which there are many, as well as the ingredients used, namely the type of malt and its level of modification.
In malting, modification refers to the extent enzymes break down the protein matrix and cell walls within the barley kernel during the germination process, creating pathways for those same enzymes to later access and convert starches to sugar. The degree of modification varies substantially between different malting approaches – whereas most modern commercial malts are highly modified, meaning the starches readily convert during a simple single infusion mash, traditional floor malting tends to result in malted grains with much lower modification that require a more rigorous mashing regime to achieve the same level of conversion.
Developed in Germany and Czechia in the late 18th century, the decoction mash is one such method that involves boiling portions of the mash, grains and all, then returning it to main mash in order to increase the temperature. This boiling process helps to break down the hard, starchy cell walls, thus making the starches more accessible to the enzymes for conversion. Initially used to increase efficiency and yield, many modern brewers believe decoction mashing also imparts unique and highly desirable flavors. I recently got my hands on some floor malted Czech Pilsner malt and decided to put it to the test.
| PURPOSE |
To evaluate the differences between a Czech Pale Lager made using a single infusion mash and one made using a single decoction mash.
| METHODS |
For this xBmt, I went with a simple Czech Pale Lager recipe with a grist made-up entirely of under-modified Pilsner malt. Special thanks to F.H. Steinbart for supplying the malt for this batch!
The Light Let Through
Recipe Details
| Batch Size | Boil Time | IBU | SRM | Est. OG | Est. FG | ABV |
|---|---|---|---|---|---|---|
| 5.7 gal | 60 min | 36.5 | 3.7 SRM | 1.042 | 1.011 | 4.07 % |
| Actuals | 1.042 | 1.011 | 4.07 % | |||
Fermentables
| Name | Amount | % |
|---|---|---|
| Czech Pilsen Malt (Floor-malted) | 10.75 lbs | 100 |
Hops
| Name | Amount | Time | Use | Form | Alpha % |
|---|---|---|---|---|---|
| Saaz | 57 g | 60 min | First Wort | Pellet | 2.2 |
| Saaz | 85 g | 60 min | Boil | Pellet | 2.2 |
| Saaz | 85 g | 15 min | Boil | Pellet | 2.2 |
Yeast
| Name | Lab | Attenuation | Temperature |
|---|---|---|---|
| Lookr (L29) | Imperial Yeast | 77% | 50°F – 58°F |
Notes
| Water Profile: Ca 41 | Mg 4 | Na 10 | SO4 47 | Cl 35 |
I used two pouches of Imperial Yeast L29 Lookr to make a single large starter a day ahead of time.
The next day, after collecting the water for two 5 gallon/19 liter batches, adjusting them to the same desired profile, and getting them heating up, I milled the grains.
With the waters properly heated, I added the grains for the decoction batch to one kettle of water to achieve the initial temperature of 144°F/62°C, after which I incorporated the grains into the single infusion batch set to maintain 150˚F/66˚C. In order to reduce the influences of extraneous variables, I planned to hold the single infusion mash for however long the decoction mash took to finish. After a 45 minute rest, I pulled approximately 1/3 of the decoction mash, placed in a separate kettle, then brought it to a 162˚F/72˚C. Following a 15 minute rest, I boiled this small portion of the mash for 15 minutes.
Next, I reunited the boiled mash with the main mash, which settled at 165˚F/74˚C, and let it rest another 10 minutes, during which I prepared the kettle hop additions.
I removed the grains from the decoction batch and proceeded to heat the wort up. This process totaled 1 hour and 47 minutes, which is how long I allowed the single infusion mash to rest before removing the grains. Both worts were boiled for 60 minutes, after which they were quickly chilled.
Refractometer readings showed the OG of the decoction batch was a bit higher than the single infusion wort. While there was a slight volumetric difference between the worts, with the decoction batch having slightly less due to boiloff, it wasn’t enough to account for the higher OG on its own, suggesting the decoction process resulted in more conversion.
Identical volumes of wort from either batch were transferred to sanitized fermentation kegs and placed in my chamber to continue chilling to my desired pitching temperature. Once both were at 48˚F/9˚C, I evenly split the yeast starter between them.
The beers were left to ferment at 50°F/10°C for a week before I gradually raised the temperature to 62˚F/17˚C over the course of a week. Following a 48 hour diacetyl rest, I took hydrometer measurements showing the decoction beer finished a bit lower than the single infusion beer.
I then gently reduced the temperature of the beers to 32˚F/0˚C over a few days the pressure transferred them to CO2 purged serving kegs, which were placed on gas in my keezer. After a 4 weeks lagering period, the beers were clear, carbonated, and ready for evaluation.
| RESULTS |
A total of 27 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the single infusion beer and 1 sample of the decoction beer in different colored opaque cups then asked to identify the unique sample. While 14 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, a total of 16 did (p=0.005), indicating participants in this xBmt were able to reliably distinguish a Czech Pale Lager made using a single infusion mash from one made with a single decoction mash.
The 16 participants who made the accurate selection on the triangle test were instructed to complete a brief preference survey comparing only the beers that were different. A total of 7 tasters reported preferring the single infusion beer, 8 said they liked the single decoction beer more, and 1 had no preference despite noticing a difference.
My Impressions: While I typically do 5 semi-blind triangle tests, for this xBmt, I went with 10 trials and identified the unique sample 5 times. Curiously, my first 3 attempts were with the beers served on tap, and I was wrong every time; my following 7 attempts happened later with beers I bottled for data collection, and I chose the odd-beer-out 5 times. These beers were very similar, though I perceived more malt aroma and fuller mouthfeel in the decoction beer, while I felt the single infusion version was slightly thinner and spritzier with less malt aroma. I preferred the decoction beer, but thoroughly enjoyed the single infusion one as well.
| DISCUSSION |
Originally developed by Czech and German brewers in the 18th century as a means of improving conversion efficiency, the decoction mash has come to be viewed by many as a method that also contributes unique characteristics to beer, namely stronger malt flavor and a fuller mouthfeel. Whereas some contend the benefits of decoction are limited to efficiency, tasters in this xBmt were indeed able to reliably distinguish a Czech Pale Lager made using a single infusion mash from one made with a single decoction mash.
In thinking of possible explanations for this result, the immediate presumption is that the decoction process had some notable impact on the flavor of these beers; however, it’s important to consider the fact the single infusion beer started with a lower OG and finished with a higher FG, resulting in an ABV of 2.9%, whereas the decoction beer was at 4.1% ABV. Since those objective differences were certainly a function of the variable, these findings seem to support the idea that decoction mashing is beneficial when using under-modified base malt.
As much as I enjoyed both of these beers, I had a slight preference for the maltier flavor and fuller mouthfeel of the decoction beer, and hence I’m wont to continue employing this arguably laborious method for classic European lagers in the future, at least when I have the time and patience. That said, I’m wholly convinced world-class lagers can be made using a single-infusion mash, and I’ve no plans to ditch this approach altogether, but I do appreciate the nod to tradition of performing a decoction mash.
If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!
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