by Spencer W. Thomas (Brewing Techniques)
Decoction brewing is surrounded in controversy in modern brewing circles. We know that, at minimum, medieval and Renaissance breweries used decoction mashing to provide predictable temperature boosts in the absence of thermometers and controlled heat for their mash tuns. The practice, however, continues to be used in home breweries and even commercial breweries in Germany and, to a lesser extent, the United States.
Adherents claim a variety of benefits of decoction mashing. Many home brewers, for example, use decoction mashing as a way to add continental malt character to their beers. At least, that’s why I use it. Darryl Richman, in Bock, emphasizes the importance of decoction mashing in brewing the extremely malty Bock style. In New Brewing Lager Beers, Greg Noonan claims that decoction provides a number of other benefits as well, including increased starch conversion, effective mashing of poorly modified malts, better hot break formation, and reduction of hot-side aeration.
No one will dispute that decoction mashing has a downside: It is a very time-consuming practice. Even a single-decoction mash adds at least an hour to the brew day. If your brewing time is already limited, you may not have the extra hours to spend in search of rhat elusive malt character.
With this in mind, I set out to investigate some alternative-ways to get increased maltiness in beers. I was intrigued by discussions on the internet mailing list Homebrew Digest about pressure-cooking wort or mash to enhance melanoidin formation for increased malt character. The interior of a pressure cooker at 10 lb of pressure easily reaches a temperature of 240 °F (115 °C). At this temperature, the Maillard reactions (one type of browning reaction) between sugars and amino acids in the wort proceed much more quickly than at normal boiling temperatures (Maillard reactions produce compounds that taste bready, toasty, and malty).
In this article, I describe and test two alternatives to the traditional decoction mash. The first involves pressure cooking all or part of the wort for part of the boil time. The second is closer to a decoction mash in that a portion of the mash is removed and pressure-cooked for a short time, then returned for the remainder of the mash schedule. The resulting beers are compared in a blind tasting with beers made using single-infusion and single-decoction mashing techniques.
The Oxford English Dictionary defines decoction as “boiling in water … so as to extract the soluble parts or principles of the substance.” Simply put, a decoction mash is one in which a portion of the mash is boiled.
Why would anyone do that? Beginning home brewers are all warned that boiling specialty grains will extract tannins and make our beer harsh and astringent. Yet decocted beers are among the smoothest and maltiest beers made. How can we reconcile these facts? A brief tour of decoction will resolve this dilemma.
The origins of decoction: Decoction mashing served two purposes in the “old days.” It provided a way to get predictable temperature steps in an unheated mash tun before the development of reliable thermometers. And, perhaps more important, it provided a way to efficiently mash poorly modified malt.
Without a thermometer, the only way to get a predictable temperature increase in the mash tun was to add a measured amount of boiling water. The problem with adding boiling water, however, is that it also dilutes the mash. If several mash steps are needed, more and more water must be added. To save the mash from a watery doom, and the tun from overflowing, the only alternative was to remove some of the liquid from the tun, bring it to a boil, and then return it to the tun. This method raises the temperature of the mash without increasing its volume.
Unfortunately, because most of the enzymes are in the liquid portion of the mash, boiling also destroys their ability to further convert starch to sugar. Though early brewers were not aware of enzymes, they must have quickly discovered the consequences of squelching enzymatic activity. Instead of taking fully liquid decoctions, they took mostly grain for all but the last decoction, with just enough liquid to keep the decoction from scorching.
This step in the development of decoction mashing led to its second benefit: Early malted barley was typically not well-modified; boiling the grain during decoction bursts starch granules and softens the unmodified tips of the malted barley, thus improving extraction efficiency and yielding a stronger beer from the same amount of malt. Again, although early brewers did not have hydrometers, they surely became aware that they could make more beer, or the same amount of stronger beer, by decocting their mash.
Decoction’s persistence today: With the advent of thermometers, heated mash tuns (not to mention RIMS systems), and modern malts, brewers today don’t require the decoction method to raise mash temperatures or to convert undermodified malt. So why do we decoct? Because of the third benefit of decoction: the flavor that it imparts.
Boiling the malt encourages Maillard reactions, which produce increased malty, toasty flavors and aromas as well as a wort of deeper color. These are the same reactions that produce the flavor in bread crust and grilled steaks. Some Maillard browning is also present in kilned malts, which is why dark malts are typically maltier tasting than light malts.
A traditional decoction schedule can include one, two, or three decoction steps and are thus referred to as single-, double-, or triple-decoction mashes. At each step, a portion of the mash is removed, heated through one or more sugar conversion steps, and boiled for 20–60 minutes.* The decoction is then gradually and smoothly returned to the mash tun with gentle mixing, raising the mash temperature to the next rest point. Many typical decoction schedules have been published, though brewers are certainly free to vary the number and temperatures of the rests according to their recipe design parameters, malts to be used, and individual brewery setup.
The graph above shows an example of a simplified triple-decoction mash schedule. In reality, of course, the rest temperatures are not constant, and holding the temperature of the rest mash (the part that is not being decocted) may require periodic infusions of boiling water or other means of heating. This four-and-a-half hour schedule follows the one recommended by Noonan. In another excellent reference, Richman provides a chart depicting a triple-decoction schedule used by the Weihenstephan brewery; that mash schedule is almost seven hours long!
Triple decoction: The triple-decoction mash is the most intensive and longest of the decoction mashes. It is suited to poorly modified malt (hard to find these days) and to beers made from a large proportion of wheat. Wheat malt has a different protein makeup than barley and is sometimes higher in protein. It has thus traditionally benefited from a protein rest, though wheat varieties differ greatly and many brewers claim good results with single infusion. You will probably choose to use triple decoction only if you wish to develop the most intense malt profile.
*Some brewers suggest that 5–10 minute boils are sufficient to achieve decent malt flavors.
A typical triple-decoction schedule starts with room temperature malt that is doughed in with cold water to prevent starch balling. About 1 quart of water per pound of grain produces a mash of the desired thickness. Another ½ quart of water per pound of grain is brought to a boil and gently infused into the mash to raise the temperature to 95–105 °F (35–41 °C) for the first step, often called the acid or low-temperature rest. While this step may not be needed for pH adjustment of many malts and waters, the breakdown of beta-glucans (gums) that occurs in this temperature range will reduce wort viscosity and ease sparging.
First decoction. After about 20 minutes, the first decoction is removed. The decoction should be made up of mostly grain with just enough water to surround the grains, and the volume depends on the amount of grain and water used and the size of the temperature step (see the box, “Calculating Decoction Volumes,” above). If the mash contains little liquid, the decoction may be as small as 30% of the mash. A thinner mash will require a larger decoction to provide sufficient heat to raise the mash temperature to the next step.
The precise amount may vary according to trial and error. For example, although the calculation shown would call for a volume of around 30% for the first decoction, I find it works best to take about 40% of the mash. I take such a large portion in part because the rest mash cools rather quickly in my mash tun. I therefore prefer to err on the larger side, because if I take too little, I’ll undershoot my next rest. If I take too much, on the other hand, I can simply let the excess cool to the rest temperature before mixing it back into the mash.
This first decoction is heated to saccharification temperature (150–158 °F [65–70 °C]) and held there until starch conversion is complete, which should take 15–20 minutes. In practice, it is easy to see the transition from cloudy, starchy wort to clear, sugary, sweet wort. Then heat the decoction to the boiling point and keep it there for at least 30 minutes, stirring as needed to prevent sticking and scorching.
The decoction is then mixed back into the rest mash gradually and gently to avoid “scalding” the mash and to minimize the amount of air mixed in. It should take about 10 minutes to completely return the decoction. Until you are used to how your system works, it may be useful to have some boiling water on hand in case you undershoot your target temperature of 122 °F (50 °C) for the protein rest of the main mash.
Second decoction. After holding the protein rest for up to 20 minutes, a second, thick decoction is taken. This decoction will need to be somewhat larger than the first because the next step to saccharification temperature is larger than the first step. I typically take up to 50% of the mash or supplement the decoction with some boiling water when I return it to the main mash.
As with the first decoction, the second decoction is heated to 150–158 °F, held briefly, and then brought to a boil. After the decoction boils for 30 minutes, it is mixed back into the rest mash to bring the temperature into the saccharification range of 150–160 °F (66–71 °C). Usually a rest temperature in the higher end of this range is desirable to develop a full-bodied malty sweetness in the finished beer (see Jim Busch’s article in “Further Reading” for a discussion of this mash rest step).
Third decoction. After maintaining the main mash at saccharification rest for 20 minutes (or when the iodine test indicates complete conversion), the third decoction is taken. Unlike the first two decoctions, this decoction is “thin.” In practice, this means that the decoction is completely liquid. At this point, we do not want any further breakdown of starch granules because no further conversion to sugar will occur; further breakdown of starches will only result in a starchy wort. I remove my final decoction by simply opening the lauter tap and running off about 40% of the mash volume.
The decocted liquid is brought to a boil, boiled for 20 minutes, and mixed back into the main mash to raise the temperature for mash-out (about 167 °F [75 °C]). At this point, the mash should be thoroughly mixed and roused and then left alone for at least 30 minutes to settle. Done properly, the decoction steps will have removed most of the air from the mash (thus minimizing the possibility of negative effects from hot side aeration), leaving it very dense. If allowed to settle undisturbed, the heavier husk particles will settle to the bottom, forming an effective filter bed, while the lighter, proteinaceous “hot break” material will settle at the top, where it will interfere least with the draining process.
Double-decoction mash: The traditional double-decoction mash schedule is identical to the triple-decoction mash except that the acid rest and first decoction are skipped. The process begins with a boiling water infusion to bring the malt from its dough-in temperature directly to the protein rest (122 °F [50 °C]). The remainder of the schedule proceeds as above, except that the saccharification rest temperature should be a bit lower to make up for the loss of the starch conversion from the first decoction.
Single-decoction mash: Single-decoction mashing is a reasonable compromise between the time demands of a full triple-decoction mash and the blandness of an infusion mash. The single decoction allows the development of some malt flavor without adding more than an hour to the brewing cycle.
The single-decoction mash starts with an infusion of boiling water to mash in to a combined protein and sugar rest at 131 °F (55 °C). In this step, large proteins are reduced to medium-weight polypeptides, which contribute to body and head retention. At the same time, beta-amylase starts producing maltose from the ends of starch and dextrin chains.
After a short rest (15 minutes), a thick decoction of 30–40% is taken, heated to 158 °F (70 °C) for saccharification, brought to a boil, and boiled for at least 30 minutes. As in any decoction mash program, the decoction is returned gradually and gently, with complete mixing, to the rest mash. This addition should bring the mash to the desired saccharification rest temperature, which is held until conversion is complete. Mash-out, if desired, can be accomplished by adding boiling water.
During decoction, important changes occur in the mash — starch is converted to sugar and dextrins, starch granules in the malt burst and gelatinize, proteins coagulate, and flavor and color are developed through browning reactions. For the purposes of this article, we are most interested in the browning processes known as Maillard reactions, complex reactions first described by the French biochemist Louis-Camille Maillard early in the 20th century.
Maillard reactions are still not completely understood. Initially, a sugar reacts with the amine group on an amino acid or at the end of a polypeptide chain. An unstable intermediate product then undergoes further changes, resulting in a variety of end products. These reactions occur rapidly at boiling temperature and higher. The result is a brown color and full, intense flavors.
The other browning reaction familiar to most of us is caramelization. This simpler reaction involves only sugar and requires much higher temperatures (300 °F [149 °C] and higher) than the Maillard reactions. The resulting caramel flavor, while pleasant, is nowhere near as complex and interesting as the range of flavors that result from Maillard browning. Interestingly, most of the flavors in caramel malts are actually due to Maillard reactions, rather than actual caramelization.
A key point to note is that the hotter the temperature, the faster the browning reactions occur. This is why a decoction (in which the grain is boiled) produces more browning and more flavor than does an infusion mash. More browning will occur when mash is boiled than when wort is boiled because the chemical composition of the mash is comparatively complex.
What doesn’t happen during decoction? A common question that occurs to brewers new to decoction is, “Why doesn’t boiling the grain extract nasty, astringent, husky tannins?” This question is often closely followed by the next, “Why doesn’t boiling the mash destroy the enzymes?”
The simple answer to the first question is “pH.” Tannins are extracted from the grain husks at pH values of 6 and higher. The pH of the mash, however, will typically be 5.2–5.5, well below this limit. In addition, mash has a relatively high protein content, so those tannins that do dissolve in it are likely to bind to a protein fragment and precipitate out.
In contrast, suppose you were to put a pound of grain into a gallon of water and bring it to a boil as you might do in extract brewing. Any acidic compounds in the malt are diluted by a larger amount of water; therefore the pH is likely to be above 6, and the tannins will happily dissolve into the water, where they will remain to impart an unpleasant astringency to the finished beer.
The answer to the second question is that after the initial rest, most of the enzymes have gone from the malt into solution. Thus, by pulling a thick decoction, you leave most of the enzymes behind in the rest mash. The enzymes that are carried into the decoction are denatured by boiling and cannot contribute further, which is one reason the decoctions are held at a sugar conversion rest before they are brought to a boil.
Recall that browning reactions occur more rapidly as the temperature increases. Thus, it makes sense to hypothesize that getting either the mash or the wort even hotter than boiling would produce more browning and thus more flavor. One way to reach a higher temperature is by cooking under pressure. In the kitchen, a temperature of 240 °F (115 °C) can easily be reached in a pressure cooker at 10 lb (psig) of pressure.
The following experiment was designed to test the hypothesis that pressure cooking of the wort or the mash can be a worthy substitute for decoction mashing.
The recipe: I chose to make a Munich Dunkel–style beer, a style in which malt character predominates and a nice, chewy malt character really makes the beer. I chose an extremely easy recipe to keep the experiment simple and to avoid introducing extraneous flavor notes that might cloud the differences between the brews (see the recipe box). The recipe therefore used only Munich malt with no specialty grains.*
The mash schedules: I set out to compare five methods: a single-infusion mash, a single-infusion mash with part of the wort pressure-cooked, a single-infusion mash with all of the wort pressure-cooked, a single-decoction mash, and a single-decoction mash with part of the mash pressure-cooked. My goal was to compare only the resulting flavors, not the mash efficiency. Because of logistical problems, it was physically impossible to brew all configurations at once and directly compare one method with another, so I decided to test a couple of different configurations in separate experimental brew sessions. After these experiments were done I decided to add an extract component, comparing an extract-based wort with the same wort pressure cooked.
The first experiment compared the worts from a straight infusion mash, a single-decoction mash, and an infusion mash with the entire wort pressure-cooked. The second experiment took place three weeks later, after I’d bottled the beers from the first brew session and freed up my fermentors. This time, I compared the worts from a straight infusion mash, an infusion wort with a portion pressure-cooked, a single boiled decoction, and a single pressure-cooked decoction. I used a different malt and a different yeast strain in the second brew session, but because I didn’t plan to compare the beers from the two sessions against each other (only with other beers from the same brew session), I did not think the differences would affect the results.
*Munich malt generally has sufficient diastatic power (DP) to convert itself. The De Wolf–Cosyns Munich malt has a typical DP of 50 °Lintner, only slightly lower than the company’s pale ale malt (60 °Lintner).
The first brew session: I split the 2 gallons of infusion-mashed wort into two 1-gallon batches. Each gallon of infusion wort was placed in a small refrigerator to ferment with worts from the same batch. This control ensured that any differences in the beers that were due to fermentation conditions could be detected as differences in the two infusion-mashed beers. No significant differences were detected in our tastings.
Single-infusion mash. I used a single infusion of 1 quart of water at 167 °F (75 °C) per pound of grist to reach a rest temperature of 154 °F (68 °C). I held the rest for one hour before sparging (no mash-out).
Single-decoction mash. The decoction mash started with an infusion of 1.1 quart of water at 145 °F (63 °C) per pound of grist to reach a rest temperature of 131 °F (55 °C), which I held for 10 minutes. I took a thick (mostly grain) decoction of about 40% of the total mash, heated it to 158 °F (70 °C), and held it for 10 minutes. I then heated it to boiling and boiled it for 20 minutes. Returning this decoction to the mash raised the mash temperature to 158 °F (70 °C), where I held it for one hour.
Pressure-cooked wort from the infusion mash. I ran the wort from an infusion mash into a pot, which I placed inside a pressure cooker with a small amount of water in the bottom (see box, “More on Pressure-Cooking Worts and Mashes,”). At 10 psig, no steam is lost from the pressure cooker.
Boiling and fermentation. The infusion and decoction worts were boiled for 70 minutes. The pressure-cooked wort was cooked for 20 minutes at 240 °F (116 °C) with one-third of the bittering hops, then boiled for another 30 minutes with the flavor and aroma hops (anecdotal evidence suggests that pressure cooking produces close to 100% alpha-acid utilization).
At the end of the boil, all worts were adjusted to a specific gravity of 1.050, chilled using a counterflow chiller, and fermented in gallon jugs using Wyeast Bohemian Lager yeast for two weeks at 50 °F (10 °C) and bottled using 0.8 oz of sugar per gallon for priming.
Second brew session: For the second experimental brew session, I made 1 gallon of single-infusion wort, 1 gallon of infusion wort for partial pressure cooking, 1 gallon of decocted wort, and 1 gallon of pressure-decocted wort.
Single-infusion and decoction mashes. I used the same methods as in the first brew session.
Partially pressure-cooked wort. Instead of pressure-cooking the entire infusion wort as in the first experiment, this time I took only 20% (about 1 quart) of the sweet wort and pressure-cooked it while the rest of the wort was boiling normally. All the hops were added to the normal boil only. The two worts were combined at the end of the boil.
Pressure-cooking a decoction. The pressure-cooked decoction mash started like the infusion mash. After 10 minutes at 154 °F (68 °C), I removed a mostly grain decoction of about 25% of the mash using a strainer. 1 placed the decoction in a bowl inside a pressure cooker and cooked it at 10 psig for 20 minutes. After cooling slowly back to 154 °F, I returned the cooked mash to the main mash and held it for an hour.
This method is not significantly quicker than a regular decoction mash because it still takes some time to get to the boil temperature and to come back down, but one benefit is that the pressure-decoction could be prepared ahead of time. You could remove a portion of the mash from a previous batch, pack it into canning jars, and then process it under pressure for 20–30 minutes to sterilize and seal the jars. (No need to worry about botulism: The high temperatures of pressure cooking destroy the spores.) This “predecocted” mash can then be added to a simple infusion mash to infuse extra malt flavor.
Boiling and fermentation. Again, after the boil the worts were adjusted to a specific gravity of 1.050 and chilled. They were fermented with Yeast Culture Kit Company Munich Lager yeast for three weeks at 50 °F (10 °C) before bottling with 0.8 oz sugar per gallon for priming.
Extract comparison: Eventually I realized that it was not necessary that the pressure-cooked wort come from an all-grain mash, so I decided to make a pressure-cooked extract beer and compare it with the same beer made without pressure cooking.
For the extract comparison, I made 3 gallons of sweet wort using Heidelburg “Octoberfest Amber” unhopped all-barley malt extract. I took about 1 quart of this wort and pressure-cooked it as I did in the first two experiments. The rest of the wort I boiled for an hour using the same hop additions as in the second all-grain experimental brew session. I then mixed the pressure-cooked wort with enough bitter wort to make 1 gallon in the fermentor. I ran 1 gallon of the remaining “normal” wort into a second fermentor. (I adjusted both gravities to 1.050.) The wort was fermented on the yeast slurry from the second session’s beers, also at 50 °F (10 °C).
The final gravities for the first batch were similar: The infusion and pressure-cooked beers came in at 1.018; a recently sampled decocted beer was at 1.016 (though as I mention later the bottle that was evaluated seemed much drier than that, indicating a localized infection).
The wort cooked in the pressure cooker came out of the cooker crystal clear with huge “egg-drop soup” clumps of hot break. It was clearly darker than the infusion wort and had a strong malty/bready aroma and flavor. The bittering seemed to be a bit lighter than in the infusion wort, but the utilization must have been reasonably close to what I anticipated. (Recall that I added only one-third of the usual bitteting hops into the pressure cooker, based on anecdotal evidence that pressure cooking produced close to 100% alpha-acid utilization.)
The infusion-mashed wort tasted good, but definitely wasn’t as interesting or exciting as the pressure-cooked wort. At that point, it appeared that I was onto a good thing. By the time I chilled and pitched the decocted wort (the last one to finish), I was so tired I forgot to taste it.
At bottling time, the infusion-mashed beer was pleasant, but somewhat bland. The pressure-cooked beer had a sweet, malty aroma and a matching flavor. Both were slightly cloudy. The decoction-mashed beer also had a malty profile, but was somewhat crisper and cleaner tasting than the pressure-cooked beer. It was clear that decoction and pressure cooking produced different end products. I preferred the decoction-mashed beer, but the pressure-cooked beer was easily my second choice.
The early results from the second brew session were similar to those of the first, although the differences between the beers were less pronounced, presumably because the whole wort was pressure-cooked the first time and only part of the wort was cooked the second time.
The pressure-cooked extract beer tasted a bit maltier at the end of fermentation than did the “straight” extract batch. Unfortunately, this experiment was marred by a couple of errors: First, the bitterness of the two beers would not be the same, and second, I put one of them into a contaminated keg, effectively terminating that portion of the experiment. (Nobody’s perfect.)
The beers were evaluated by various judges under differing conditions. The table, “Summary of Judges’ Comments,” shows the results of all the judging. The evaluations are summarized below.
The beers from the first brew session were informally tasted at a meeting of the Ann Arbor Brewers Guild after they had been in the bottle for only a week. In general, the comments matched my impressions at bottling time.
The beers from the second brew session were tasted by a group of experienced BJCP judges (ranging from Recognized to National status) at another meeting of the Ann Arbor Brewers Guild on November 14, about six weeks after brewing and three to four weeks after bottling. The beers were not formally judged on the 50-point BJCP scale, but were instead ranked in terms of malt character. The results, from least malty to most: Infusion, pressure-cooked decoction, pressure-cooked infusion wort, and the straight decoction. The character of the pressure-cooked decoction beer was judged as being somewhat “corny,” similar to the flavor and aroma of DMS. One judge remarked, “This one is decocted!” after his first sniff and sip of the decoction beer.
A second group of three judges of varying experience and I participated in a specially arranged blind tasting of all the beers (from all three batches) at the end of November. Again, we did not formally assign points, but instead concentrated on malt character and our overall impressions. One thing we learned is that after several malt-accented beers, it’s harder to pick out the malt profile in the remaining beers!
The beers were presented in pairs, with beers explicitly compared only against other beers from the same brew session. The judges knew that the experiment involved developing malt character in beers, which may explain why they seemed to be straining for differences. At this point, the decoction beer from the first batch had dried out significantly in the bottle, to the point where it was almost astringent and definitely overbalanced to the bitter side. The comments shown in the box clearly reflect these flaws. Another bottle sampled recently tasted fine, so the problem with the bottle judged must be attributed to a bottle sanitization problem.
As is usual in beer judging, the comments exhibit a wide range of variance in perception and opinion. One judge definitely preferred both infusion-mashed beers over all the others. When asked why, he opined that they were “smoother.” In general, though, it appears that pressure-cooking methods did increase the malt character in this beer. Between the two pressure-cooked beers, there appeared to be a slight preference for the pressure-cooked wort over the pressure-cooked mash. Except for the flawed first decoction beer, all were very drinkable, pleasant beers.
If you’re looking to increase the malt character in your beers but don’t have the time or energy for a full-blown decoction mash, try using a pressure cooker. Although I was not able to compare the extract brews, there appears to be no reason why extract brewers can’t also pressure-cook at least part of their wort for increased malt character. A “pressure canner” with a capacity of about 20 quarts will hold an 8-quart pot and can thus cook up to at least 6 quarts of wort without threat of it boiling over inside the cooker. This “boiled decoction of an extract wort” is sufficient to add a nice maltiness to a 5-gallon batch of beer, or perhaps to push an already malty beer “over the edge.” The pressure-cooking step can take place while the rest of the wort is boiling without adding any extra brewing time at all.
As with almost any experiment, this one probably raised more questions than it answered. I would still like to take an extract brew comparison through to completion. What would happen with longer pressure cooking — say 30, 40, or even 60 minutes? What would happen with a lighter recipe (for example, a Pilsener)? How about starting with a more complex recipe containing some caramel malts and maybe a touch of dark malt? What about pressure-cooking first runnings, which have a much higher sugar and peptide concentration?
Maybe some of you can answer these questions and let the rest of us know in another article!
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