Dunkel by the numbers

OG          11.5–13.3 °P (1.046–1.055 SG)
FG           2.9–3.3 °P (1.012–1.013 SG)
Attenuation         68–75% (apparent)
SRM       18–28 (usually about 20)
IBU         20–26 (usually about 22)
ABV       4.8–5.6%

The Bavarian dunkel lager — as well as its darker siblings, the schwarzbier and the rauchbier — is the historical precursor of all modern lagers. These include the Bavarian helles, Märzen and Oktoberfest, bock beers, the Vienna lager, the Bohemian pilsner, the Dortmunder export, the German pils, and even the North American pilsners.

Dunkel is the German word for “dark.” It refers to the deep brown, mahogany or sepia color of this opaque, all-barley lager. From the early sixteenth to the late nineteenth century, dark lagers were the most common beers in Bavaria. Initially called red beers, they came to be called by their modern name only in the 1840s, probably to distinguish them from the growing variety of paler lagers that were being introduced at that time.

The First Beer Style . . . By Law!

Before the introduction of the indirect-heat kiln in the early nineteenth century, which allowed maltsters to make pale malt, all beers were more or less dark. Depending on the climate and the season, the beers were either ales or lagers. Most beer became ales. Worts were inoculated with airborne, top-fermenting yeasts and underwent uncontrolled fermentation in unrefrigerated, open vats. In 16th century Bavaria, yeast was not even considered a necessary ingredient of beer making. Instead, it was regarded as byproduct of putrefaction and discarded. Beers would be lagers only in the winter in colder regions, such as Bavaria, when ale yeasts would be dormant and only bottom-fermenting yeasts were still active. These medieval beers often tasted sour and medicinal, especially in the summer when the chance of infection from wild yeasts and bacteria was greatest. Brewers would use any number of strong herbs and seeds to cover up the bad flavors.

The famous Bavarian Beer Purity Law of 1516, the Reinheitsgebot, began a momentous process that would change beer-making not just in Bavaria, but the entire world. After 1516, Bavarian beer could be made only from water, malted barley and hops. The importance of yeast in beer making had not yet been discovered, which is why the decree did not mention yeast as a beer ingredient.

In spite of the Reinheitsgebot, however, summer beers remained of poor quality. In 1553, therefore, the Bavarian ruler simply forbade all brewing between April 23rd and September 29th. As a result of these two regulations, a new beer evolved. Initially called red beer, it was always a dark lager, barley-based and flavored with hops. Fixed by government decree, it became the staple beer of Bavaria — this was the world’s first legally recognized beer style.

During the early decades of the nineteenth century, the new lager beer style spread from Bavaria to neighboring Austria and Bohemia. As pale malt became available around that time, brewers started to create blond lagers as well. After the invention of refrigeration near the end of the century, cold-fermenting lagers replaced ales as the favorite beers in all parts of Europe except for the lower Rhineland of Germany, Holland, Belgium, Britain, Scotland and Ireland.

Dunkel Profile

The dunkel, like all Bavarian-style beers, tends to be low in hop bitterness. Brewed with a large portion of Munich malt, dunkels are soft, elegant and well-attenuated with almost no nose. They have a rich, malty, mildly vanilla, nutty-sweet palate and a dry, rounded finish that is never harsh, toasty or acrid. The diacetyl level must be well below the taste threshold, and thus notes of butterscotch — typical of many British dark beers — must be totally absent.

Ingredients

The foundation grain of a typical dunkel is Munich malt, which is also  called dunkel malz or Münchener malz in Germany. Dunkels are often made from about 30% Munich malt with a color rating of 10° Lovibond (L) and about 15% Munich malt with a color rating of 20° L. For extra color, flavor and body, you can also add up to 15% caramel malt (60° L) and about 5% dextrin malt, such as CaraPils. Perhaps surprisingly, the rest of the grain bill —about 35% — is made up of pale pils malt (helles malz) with high enzymatic strength, a color rating below 2° L, and a protein content between 11 and 12%. (See the five-grain dunkel recipe on page 19 for instructions on how to brew this type of dunkel lager beer.)

It is also possible to make a dunkel entirely from a nine-to-one mixture of 10° L and 20° L Munich malts, but such a grain bill tends to produce a much lighter-colored, almost amber brew. (See the all-Munich dunkel recipe on this page, to the left, for instructions on how to brew this dunkel variation.)

Munich malts are produced from the same grains as pils malt, but are kilned longer and at slightly higher temperatures. Some are lightly roasted, but never burned. They add body, and some sweetness, to the beer. Never use black or severely roasted malts, therefore, as you would for color in a porter or stout, not even in tiny quantities! They would add roasted notes to the beer and make it non-authentic.

North-American-grown grains are perfectly acceptable for brewing Bavarian lagers, because the protein levels tend to be comparable to those of continental-European grains. Avoid barley varieties grown for ales in the maritime climate of the British Isles, such as pale ale malts. Their protein levels can be as low as 9%, which tend to be insufficient for the full-bodied texture, rich mouthfeel and creamy, long-lasting head of a properly made dunkel lager.

When brewing with extract, choose a pale German-style lager malt extract as a substitute for the pale grain. Choose a dark lager malt extract as a substitute either for all the other malts (see the extract version of the second recipe), or for just the Munich malts, if you are planning a partial mash (see the extract version of the first recipe).

Because the ratio between “specialty” (non-pale) and foundation (pale) malts is essentially reversed in a dunkel, a partial mash that would include the Munich malts would be impractical. If you choose just straight dark lager malt extracts, you still have the option of steeping the specialty grains for extra flavor. Alternately, you can make a mini-mash of the Munich and specialty malts and add light malt extract for the remainder of the fermentables for the beer.

Because malt, not hop, flavors dominate in a dunkel, use only German-type noble varieties for bittering, flavor and aroma. Hallertauer Mittelfrüh, Hersbrucker, Tettnanger, Spalt, Perle, Northern Brewer and Mount Hood are the best choices.

Ferment your dunkel with any of the standard Bavarian-style lager yeasts — such as Wyeast 2206 (Bavarian Lager) or White Labs WLP830 (German Lager) — but note that dark lagers tend to be fermented at a slightly higher temperature than blonde lagers. Whichever yeast you pick, it must be slow acting and capable of fermenting at an optimum temperature of 50-59° F (10-15° C).

Step Infusion Dunkel Mashing

In the old days, dunkels — like all Bavarian lagers — were made from decoction mashes. But with modern grains, infusion mashing is replacing decoction mashing even in German breweries. For authenticity, though, you should definitely use a multi-step mash schedule. To raise the temperature from one step to the next, use hot water. There is no general rule for the temperature of your infusion water, because it depends largely on the thermal absorption characteristics of your equipment; in other words, how much heat your brewing equipment absorbs (and radiates) while you brew. Use boiling hot water, if necessary. You can also apply direct heat to your mash tun.  When directly heating the mash, you should stir the mash slowly but steadily. Strring slowly minimizes aeration. Stirring steadily helps avoid scorching.

The entire mash cycle may take anywhere between 90-150 minutes for a step-infusion mash, depending on your choice of starting temperature and on the number of rests. Below is an outline of a complete mash schedule for a typical dunkel mash. If you are in a hurry, feel free to skip the lower-temperature rests, but be aware that you will sacrifice authenticity.

If your equipment allows you nothing but a single-step infusion mash, ignore the schedule below and aim for a compromise temperature of about 154° F (68° C) for about one hour, but your beer will likely lack the richness and creaminess that you would expect in a dunkel!

Protein-converting enzymes work best in thick mashes, while starch-converting enzymes work best in thin mashes. In a multi-step mash, therefore, it is always best to “dough in” as thick as possible rather than to “mash in.” This is good for enzymatic action, and it leaves enough room in the mash tun for plenty of hot-water additions to raise the mash temperature. The precise ratio of grain to water at the dough-in stage is not relevant, as long as the grain is at the right temperature and there are no dry pockets.

As an optional step, you can start out with an acid rest for 15-30 minutes at 100 ± 5 °F (38 ± 2 °C). Many German brewers believe that an acid rest improves extract efficiency if you hydrolyze enzymes, starches and proteins at this temperature.

If you skip the acid rest, dough in directly at about 122 °F (50 °C) for a protein rest of about 30 minutes. Otherwise, raise the temperature using a small quantity of hot water and external heat, if necessary. Mash temperatures in the range of 113-122 °F

(45-50 °C) also yield the largest amount of free amino nitrogen (FAN), simple amino acids that are essential for healthy yeast growth and yeast metabolism later on in the fermenter.

Next, increase the temperature to 146 ± 2° F (63 ± 1° C) for a beta saccharification rest of about 30 minutes, then to 156 ± 2° F (69 ± 1° C) for an alpha saccharification rest of about 30 minutes. Now you can use plenty of hot water for the temperature increase, because thinner mashes favor diastatic conversion. Also, because a dunkel is a relatively dry beer, it is essential that you give the diastatic conversion a full one-hour rest.

Finally, raise the temperature to 170° F (77° C) for the mash out and start sparging. For less trub in the kettle and a crisper, haze-free final beer, recirculate your wort. Immerse a pitcher in hot water (to keep it from acting as a heat sink), collect the first runnings and pour them back on top of the grain bed. After recirculation,  sparging  should take about 90-120 minutes.

From Boil To Bottle

All-grain brewers should boil their dunkel wort for 90-120 minutes. Extract brewers may employ a shorter boil, from 45 minutes to an hour. Add the bittering hops 15 minutes into the boil — never earlier! German wort has plenty of proteins, and because uncoagulated proteins envelop unisomerized alpha acids, you get less hops utilization out of your bittering hops. German brewers prefer to wait 15 minutes to let the proteins coagulate. Add the flavor hops 10-20 minutes before the end of the boil (or as late as at shutdown).  Add the aroma hops near, at, or shortly after the end of the boil.

Chill the wort to at least 55-65° F (13-18° C). The optimum primary fermentation temperature is 50-59° F (10-15° C). Use two packages, containers, or pouches of yeast, or make a yeast starter to increase the yeast count. Vigorous primary fermentation usually takes about seven days. At a gravity of about 4-5° P (1.016-1.020 SG), rack the brew into a secondary fermenter and leave it there for another two weeks.

Then transfer the beer for lagering. Lager your dunkel as close to the freezing point as is possible for about four to six weeks. You can lager at temperatures as low as -2° C (almost 28° F). During lagering, the remaining yeast in suspension reabsorbs or reduces a good portion of its less desirable metabolic byproducts, such as esters, aldehydes, fusel alcohols and diacetyl. This makes the beer taste clean and crisp. The yeast also scavenges oxygen, which increases beer’s shelf life. After lagering, rack off the debris one more time and prime with about 1/2 cup of corn sugar or dried malt extract. Alternatively, add about half a teaspoon of your priming agent into each 12-ounce bottle and siphon carefully out of the lagering container.

Horst Dornbusch is the author of “Prost! The Story of German Beer.” Starting with this issue, he’ll write “Style Profile” in every edition of BYO.

Decoction Tips

At mash-in, infuse your grain with up to 70% of your brewing liquor and reserve the remaining 30% for sparging. To raise the temperature of the main mash from one level to the next, draw one-third of the main mash into a separate cooker for a decoction boil of 10–20 minutes. Some German breweries boil about one-half of the mash during the final decoction and boil this for almost one hour. During the decoction, raise the temperature slowly at a rate of about 2 °F (1 °C) per minute. For improved saccharification, you can give the separate decoction mash an optional 15-minute rest at a temperature of 152–154 °F (67–68 C°). Then reintroduce the decoction mash into the main mash. Do this once for each step.

Five-grain Dunkel

(5 gallon, all-grain)

OG = 1.048  FG = 1.012 

IBU = 22  ABV = 4.6%

Ingredients

3.6 lbs. two-row lager malt

2.7 lbs. Munich malt (10° L)

1.4 lbs. Munich malt (20° L)

0.9 lb. caramel malt (60° L)

0.5 lb. CaraPils malt

5 AAU Hallertauer Mittelfrüh (1.25 oz. of 4% alpha acid)

0.5 oz. Tettnanger hops (flavor)

1 oz. Tettnanger hops (aroma)

2 packs of one of the following:

   Bavarian Lager (Wyeast 2206),

   Munich Lager (Wyeast 2308),

   Southern German Lager (White Labs WLP838) or

   Old Bavarian Lager (White Labs WLP920)

1/2 cup corn sugar (for bottling)

Step By Step

Step mash with 30-minute rests at 122° F, 146° F and 156° F. Alternatively, do a single-infusion mash at 154° F for an hour. Heat mash to 170° F prior to recirculation and sparging. Collect 6.5 gallons of wort. Boil for 90 minutes. Add bittering hops after the first

15 minutes of boil. Add flavor hops with 15 left in boil and aroma hops at the end of the boil. Cool wort. Aerate and pitch yeast. Ferment one week at 55°F, then rack to secondary and ferment an additional two weeks. Lager for 4–6 weeks at 28° F. Bottle and serve. See article for details.

Extract with grains option

Substitute 3.75 lbs. Bierkeller Plain Dark malt extract and 2.75 lbs. of either Bierkeller Plain Light or Irek’s Munich Light malt extract for the 2-row and Munich malts. Steep the caramel and CaraPils malts in 150° F water for 15 minutes. Remove grains, add malt extract and bring wort to a boil. Follow all-grain instructions from this point forward.

All-Munich Dunkel

(5 gallon, all-grain)

OG = 1.048  FG = 1.012  IBU = 22 

ABV = 4.6%

Ingredients:

8 lbs. Munich malt (10° L)

1 lb. Munich malt (20° L)

5 AAU Hallertauer Mittelfrüh (1.25 oz. of 4% alpha acid)

0.5 oz. Tettnanger hops (flavor)

1 oz. Tettnanger hops (aroma)

2 packs of one of the following:

   Bavarian Lager (Wyeast 2206),

   Munich Lager (Wyeast 2308),

   Southern German Lager (White Labs WLP838), or

   Old Bavarian Lager (White Labs WLP920)

1/2 cup corn sugar (for bottling)

Step by Step

Step mash with 30-minute rests at 122° F, 146° F and

156° F. Alternatively, do a single-infusion mash at 154° F for an hour. Heat mash to 170° F prior to recirculation and sparging. Collect 6.5 gallons of wort. Boil for 90 minutes. Add bittering hops after first 15 minutes of boil. Add flavor hops with 15 left in boil and aroma hops at the end of the boil. Cool wort. Aerate and pitch yeast. Ferment for one week at 55° F, then rack to secondary and ferment an additional two weeks. Lager for four to six weeks at 28° F. Bottle and serve. See article for further details.

All-extract option

Use 7 lbs. Bierkeller Plain Dark malt extract, or a combination of 6.2 lbs. Bierkeller Plain Dark and 0.8 lb. Irek’s Munich Amber malt extract. Do not use any of the Munich malts listed in the all-grain recipe.

Bring 6 gallons of water to a boil. Shut off heat and stir in extract. Boil the wort for 60 minutes. Add bittering hops after the first 15 minutes. Add flavor and aroma hops toward the end of the boil. Cool the wort to at least 65° F.  Siphon the wort to your fermenter and aerate thoroughly. Pitch yeast, ferment and lager as instructed in the article.