A Matter of Immense Gravity
Some Tricks to Successfully Brewing Strong Beers
By Jim Busch (Originally published in Brewing Techniques Magazine - Volume 4, Issue 2)
Brewing ales and lagers with a high alcohol content can be difficult for the uninitiated. Dealing with the complexities inherent to these beers calls for rethinking some of your techniques, but the reward of a special, festive beer makes the challenge worthwhile.
For brewers, any Starkbierfest presents not only the satisfaction and warmth of enjoying the finished product, but also the opportunity to showcase their skills in these hard-to-brew beers.
Jim Busch is an electrical engineer developing satellite communications systems for NASA at the Goddard Space Flight Center in Greenbelt, Maryland. Jim’s been an all-grain brewer since 1989, and when he’s not beer hunting, he’s often in his backyard brewery (with his Labrador retriever, Dunkles) that he designed and built in 1992.
What Is a Strong Beer?
Strong beers — beers with an original gravity of 1.064 or higher — require special handling from initial recipe formulation through the all-important fermentation and all the way to the aging and packaging of the finished beer. The brewing of strong beers can be divided into two classes based on original gravity: beers between 1.064 and 1.084, and beers above 1.084. This division is somewhat arbitrary, but as beers develop alcohol levels above 8% (v/v), their complexity and character change, as does the level of difficulty for the brewer.
Before I jump into the process of brewing strong beers, I should summarize the types of strong beers currently in commercial production. Strong beers are like all other beers in at least one respect: they come in two classes, ales and lagers. Typical strong lagers include Bock, Hellesbock (or Maibock), Doppelbock, and Eisbock. Strong ales include Belgian strong ales (including tripel and Grand Cru), Weizenbock, old ale, wee heavy, imperial stout, and barleywine. Brewing strong ales is somewhat more forgiving than brewing strong lagers; the abundant esters produced, combined with the higher hopping levels, are more at home in ales than in lagers.
It is important to start with a good idea of the desired characteristics of the finished beer. Should it be light in body but high in alcohol, or should it be heavy and malty with a warming alcohol finish? Should the drinker be able to tell how strong the beer is? Should the beer be aggressive in malt and hops but still balanced? Should the fermentation yeast by-products be evident to the drinker? All of these factors are controllable by the brewer, given enough forethought.
Strong beers such as barleywines should have a clearly evident malt base blending into a sweet to semidry finish with a warming alcohol end. Strong beers such as Belgian tripels should have a light malt profile, a spicy hop and yeast signature, and deceiving alcohol levels. Bock beers are typically malty and rich, but with a reduced yeast signature compared with strong ales. (A German brewer once told me that when drinking the best Bock beers, drinkers should not be aware of the alcohol level until they get up to leave!) Abbey ales are often quite dark in color but have little to no caramel or dark malt sweetness. It is a challenge to devise a recipe and method that bring out these various qualities at will.
The first choice the brewer encounters in brewing strong beers is the type of malts to be used. While it is technically possible to brew many styles of beer with what are considered “incorrect” types of malt (for example, a pale ale made with Pils malt), it is always better to pair the malt choices to the style to be brewed. To make a classic Doppelbock, you would be best advised to use German Pils and Munich malts. In the same vein, an English barleywine will be more authentic if British pale ale malt is used. Belgian ales are usually brewed with Belgian Pils malt, but German Pils is a good substitute.
The choice and quantity of specialty malts is also important. The use of caramel malts should be limited in some styles because the quantities and types of base malts used already can lead to a greater color, sweetness, and fullness of palate — particularly when using large quantities of English pale ale malt or German, Vienna, and Munich malts. The amount of dark malts used in imperial stouts can easily be overdone; recipes heavy in black patent malt can be overpowering and harsh. When brewing a new recipe, it is often best to be slightly conservative on dark malts and then revise the recipe next time the beer turns out too light. Overuse of dark malts, roasted barley, chocolate, and, in particular, black patent, can lead to a distinct burnt astringency. Even a dark, malty Doppelbock should be designed to blend and marry the individual flavors and malts.
Mashing is a variable that can make a significant impact on the overall perception of the beer. As significant factors in mouthfeel, a finished beer’s body and sweetness are the direct result of your mash rest temperature. When brewing very high gravity beers, it can be important to include a rest in the range of maximum beta-amylase activity, 140–149 °F (60–65 °C). This rest will help increase the fermentability of the wort and increase the apparent degree of attenuation. Conversely, when brewing a beer intended to finish sweet, such as a Scottish wee heavy, it is important to avoid this range of maximum maltose production. To obtain the rich toffee and malty notes of the best Bocks requires the use of decoction mashing or at least some German melanoidin malts. Belgian aromatic malt is sometimes used to increase malty aromas.
Adjuncts: Brewing adjuncts sometimes evoke a grimace from craft and home brewers. Our first awareness of adjuncts usually comes through mass-produced lagers made with 20–50% corn or rice. Brewing adjuncts also include simple sugars and flaked maize. A genuine Belgian tripel, however, cannot be made without sugar comprising 20% of the fermentables; this formulation is crucial when making a 9% (v/v) beer that does not have the body of a barleywine.
Such a high percentage of sugar fermentables may be cause for concern; it is well known that large percentages of sugar can be detrimental to fermentation because of the associated reduced level of free amino nitrogen (FAN) (1). In strong beers that contain considerable malt, however, plenty of FAN is available. It is in lower gravity beers that the lack of FAN can lead to serious fermentation problems. Sugar can be used in the form of candi sucre, corn sugar, or even cane sugar. It is important to use very light sugars in light beers, whereas darker abbey beers obtain much of their color from caramelized candi sucre (or caramel coloring), not from the use of specialty malts.
The subject of hops is too broad to allow discussion of specific hops suitable to the various high-gravity styles. What can be said in general terms is this: High hop levels tend to mellow and blend into the overall character of the beer over time. Some barleywines are considered harsh when young, but the hops and bottle conditioning mellows this effect of immaturity.
Choosing the right yeast is the most important factor in brewing strong beers. Pick the wrong yeast, and it will leave its mark on the beer. The beer may not even be able to continue to ferment above a certain alcohol level.
Strong beers require even more yeast cells to be pitched than normal beers. The typical yeast requirement for any beer is 1 million cells per milliliter of wort per degree Plato; a 23 °P tripel should be pitched with 23 million cells/mL. The best way to obtain this quantity of healthy pitching yeast is to brew a normal-gravity beer and repitch the yeast into the high-gravity wort. If you want to brew 5 gallons of 25 °P barleywine, start by brewing 5 gallons of 13 °P ESB and repitch from that fermentor into the barleywine. Another great source of this much yeast is the unitank of a quality microbrewery. Try to pitch at least 1 oz of yeast slurry per gallon of high-gravity wort.
The importance of proper wort aeration is even greater with strong beers, so be sure to use some form of aeration system (2).
Home brewers are often tempted to use Champagne yeasts in high-gravity brewing because Champagne yeasts have been selected over time for their high alcohol tolerance. In general, such yeasts are unnecessary and in some cases can result in a beer that is too attenuated for its style. Most brewers’ ale yeasts are alcohol tolerant to at least 10% (v/v), and lagers to at least 8% (v/v). There are several examples of commercial lagers and ales above 10% (v/v) (Samiclaus lager and Bush/Scaldis, for example), and these beers are fermented with regular brewers’ strains. I always prefer a strong beer fermented with regular brewers’ yeast, because the yeast fermentation by-products and attenuation seem more natural and in style. The use of Champagne yeast is a corrective option for hung fermentations, but I would aim to use normal yeasts first.
Strong beers that are pitched with sufficient yeast can undergo fairly normal fermentation, but it may appear violent and exhibit a very large kräusen layer. If fermenting in a carboy, it’s a good idea to use a blow-off tube or to place the carboy inside of a larger bucket to help catch some of the overflow. Open fermentors are excellent for strong beers, because the kräusen can be skimmed off and trub and bitter resinous material can be scrubbed out.
Never reuse yeast from a strong beer’s fermentation; high alcohol levels are very harsh on the yeast cells, and higher mutation rates can be expected.
When brewing Bock beers, it is essential to perform extended lagering as close to 31 °F (–1 °C) as possible. This lagering should last for eight weeks or longer to produce the cleanest flavors. Ales can benefit from a few weeks or months in a secondary fermentor before packaging.
Many strong beers require an extended period of aging to blend the aggressive flavors. This aging process can be accomplished in secondary fermentors if desired, in Cornelius kegs, or in bottles. The challenge is to end up with a mature beer with proper carbonation levels.
Fermenting beers to 8% alcohol or more can be very hard on the yeast cells. At the end of the fermentation, these cells may be incapable of refermentation in the bottle, so special care should be taken to help out the yeast.
For most strong beers, it is helpful to rack the beer to a secondary fermentor after primary fermentation is complete to settle out the yeast. Settling can be enhanced by placing the fermentor in a stable, cold area or in a refrigerator. The intent of the cold-conditioning period is to drop out the old yeast and trub so they can be removed before packaging. After the yeast settles out, the beer can be racked into a bottling bucket, and freshly cultured yeast slurry and sugar can be added to assist in the bottle conditioning.
For a 5-gallon batch, the slurry from 1 pint of yeast culture should be more than adequate to provide enough healthy young yeast cells to referment in the bottle. The yeast starter can be allowed to ferment out completely. Then decant the beer and discard, leaving healthy, clean slurry to repitch. Take care not to add too much slurry; adding too much slurry can accelerate autolysis, which can lead to staling flavors in the beer. If you are kegging strong beer, adding slurry is not required because the beer can be artificially carbonated, but it is still an option.
The addition of freshly cultured yeast is not always required, but if you attempt to bottle without this step the beer should not be cold-conditioned before bottling for fear of leaving the yeast dormant and incapable of refermentation. Beers that are bottle-conditioned with fresh yeast tend to carbonate and mature more rapidly than beers packaged without fresh yeast. An added benefit of using fresh yeast is that you can use a yeast strain different from the fermentation strain, a practice quite common in Belgian ales and German Weizens. The only risk with this procedure is the possibility of the bottling strain having a significantly higher attenuation level than the fermentation strain, which could lead to overcarbonation in the bottle. Bottling with different strains is also useful because some bottling strains flocculate better than others. A well-chosen conditioning/packaging yeast can result in a clearer beer that is easier to pour. Some strains can literally “clean up” fermentation by-products, which can be desirable, depending on the beer style.
The main problem facing high-gravity beers is the dreaded stuck fermentation. The best solution for stuck fermentations is to prepare for it and thus prevent it from occurring by aerating the wort and pitching enough yeast.
If you have a stuck or hung fermentation, you have several options. The first thing to do is to move the fermentor to a warmer location. This alone can often revive a sluggish fermentation. Sometimes it is useful to rouse the yeast each day by shaking the carboy or by stirring carefully if using an open fermentor. This process should never add air to the partially fermented beer, lest the alcohols oxidize into unpleasant aldehydes. Another option is to repitch with a large, new yeast culture. For this to be successful, a very large yeast slurry is usually required to overcome the alcohol levels in the fermentor. This option is a good one if you have a willing microbrewery from which to get yeast slurry. I suggest racking off the original yeast and racking onto the new yeast slurry.
Strong beers are ideal for “laying down,” which just means to place in a dark corner of the cellar (and not drinking) for months or years. Ironically, most strong ales are ideal for laying down, whereas Bock beers (lagers) tend to be best when consumed fresh. As beers age, they inevitably oxidize, creating elevated sherry and vinous notes. Many people prefer strong ales to have these characteristics, while others do not. Over time, beers made to lay down do develop complex aromas and flavors. I know brewers who make a “keeping ale” each season and save a few bottles for years. It’s the perfect beer for special festive occasions.
Brewing strong beers has always been a special event for brewers and some lucky drinkers. Strong beers are often brewed for special seasonal occasions, like the Starkbierfest in Munich, and the patrons fondly await the coming of these events. Drinking these special beers during festive times is quite memorable, but no less memorable than the lessons learned in brewing them successfully.
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