by W.L.
June 2004
The art of brewing, from its humble beginnings in ancient Sumeria to the multi-million Hectoliter industry of today has been, like all crafts, an evolving process of tradition and time honored methods versus cutting edge technology and the ever present specter of competition. Brewing will of course continue forever, however, declining consumption of beer as such, in major markets like Europe and the United States, forces the prudent brewer to keep abreast of current industry trends and to adapt accordingly or risk being sidelined by more innovative rivals. The prudent brewer should also keep an open mind regarding the diversity of methods and differing styles available. Such knowledge can only strengthen his/her mastery of the craft. As the saying goes, one should not “see the tree, but miss the forest.” This is not to say that all brewers should adapt. Those lucky enough to have a loyal following such as Augustiner Bräu in Munich can afford to brew as they always have. On a larger scale, the German Reinheits Gebot also (fortunately) protects brewing traditions as well as ensuring a familiar and quality product for consumers.
In the spirit of diversity then, this brief paper will focus one style of beer – Cask Conditioned Ale. All aspects will be discussed, from a general description of the genre and its history, to how it is produced and, most important - how it is served.
What is Ale?
To define Cask Conditioned Ale, one should first ask, what is ale? The history of ale goes back to the beginnings of English civilization (almost every civilization has some sort of fermented beverage). As such, one could write several books on the subject.
When the Angles, Saxons, Jutes, and Danes invaded and settled England in the fifth and sixth centuries, they brought with them their word for malt liquor which is öl and is the root for the modern word ale. Öl referred to a beverage made with malted grains, but without the benefit of hops (Sutula 1999, pp 12). These earliest of English beers are believed to have been brown in color. This beer, “the beverage of Robin Hood”, would have been made from malt that was brown and smoky as the result of kilning over a hardwood fire (Daniels 1996, pp 215). Hops came into use by English brewers in the 15th or 16th centuries after Dutch traders brought cultivated strains to the isle. Initially ale referred to unhopped malt liquor, and beer (from the Germanic word bier) to the hopped version. By the 1800´s, all malt liquors were hopped, and the original designations became almost synonymous (Sutula 1999, pp 35).
The Industrial Revolution came to England in the 18th century and the subsequent production of coal and steel allowed for better kilns and malting procedures that resulted in lighter colored beers (Daniels 1996, pp 154). By now, several different types of ale were available, and it becomes hard to classify them in specific groups without going into lengthy details. Further developments in the 19th and 20th centuries such as the introduction of bottled beer and glass drinking vessels, refrigeration, pasteurization, filtration, and artificial carbonation have affected the ale genre (as well as all other beers.) For reference then, the following chart (Fig 1) is presented as an aid on the current state of ales:
What is Cask Conditioned Ale?
After ale is brewed and undergoes primary fermentation (traditionally in an open fermenter), the choice of method for secondary fermentation determines whether an ale is cask conditioned or not. “Real Ale” is defined as: A name for draft, or bottled beer brewed from traditional ingredients, matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous Carbon Dioxide (Sutula, pp 153).
Real Ale hence, is ale that undergoes secondary fermentation in either a cask or a bottle. If it is the cask, then it is termed “Cask Conditioned Ale.” Cask ale was quite common in the days before the efficiency of refrigeration and modern methods of carbonation and dispensation rendered it almost extinct.
Breweries would rack their beer while it was still fermenting, directly into casks, delivering them that day to pubs and restaurants. The pubs would store the casks in relatively cool cellars, dug into the earth. From there, the beer would be hand-pumped up to spigots at the bar (Cizauskas, 1998). Traditionally, wooden casks were made out of English oak. Casks typically used were the Firkin (approx 41L) and the Kilderkin (approx. 82L). Making these casks is an art in itself (called Coopering) that goes back to antiquity (Foster, pp 71). Nowadays, stainless steel or aluminum casks are used.
Generally, the ale is racked straight from the primary fermenter into the cask. This means that the yeast cannot be filtered out. At this time, it is also primed with additional fermentable material for carbonation, dry hopped (the addition of hops to the cask to add aroma and hop character without adding significant bitterness), and finings are added (clarifying agents that precipitate suspended matter, most commonly isinglass - made from the processed swim bladders of fish, is used.)
The ale is now in the conditioning or maturation phase and is delivered sealed in this “primed and loaded” state to the local pub. The “local” aspect of cask ale is one of its defining benefits, but can also be seen a double edged sword in that it limits production and transport. As such, cask ale is meant to be local and fresh.
Since ale yeasts cease to ferment below about 10 ° C, care must be taken to keep temperatures above this minimum (how high is of course dependent on the strain of yeast). Exceedingly high temperatures cause the ale to “get too sour and acid, with too active a head”. High temperatures also allow for infections to grow faster, and affect aroma, taste, and clarity. Too low a temperature and the ale is flat, the secondary fermentation takes too long, chill haze occurs, and flavor sensations are masked (Nemeth, 1993). Optimum serving temperature is also around 10° C to 13° C.
Conditioning is traditionally done as a cooperative relationship between the brewery and pub. This requires pub personnel skilled in what is known as cellarmanship – the art of handling cask conditioned real ale. According to custom, a cellarmaster handles the cask and determines when it is ready for dispense. It is a complex discipline that requires the understanding of many variables and the nuances for each particular beer handled (Sutula 1999, pp 168).
In the pub cellar, living yeast cells in the sealed cask continue the process of secondary fermentation. The cellarmaster places the cask onto a stillage, a wooden device used to prop up and hold the cask in position for dispense. The cask remains immobile on the stillage from the time of delivery until the time its contents have been emptied. It is imperative that the cask remain undisturbed to prevent sediment from clouding the ale.
After 2-3 days, the cask is broached. This is done by driving a soft spile (a porous wooden peg) into the shive (a round plug device on the top center side of the cask). The spile is essentially a primitive CO2 valve allowing the cellarmaster to control the natural carbonation of the beer. As conditioning continues, excess CO2 is forced through the soft spile (observed as frothing foam). As frothing subsides, the porous spile is replaced with a hard (i.e. non porous) spile. Exactly when to do this is something learned only through experience, usually 36-48 hours after the start of conditioning. Once the hard spile is in place, the cask is left for a few more days until it has “fallen clear” i.e. the ale is clear and bright (Foster 1990, pp79).
The cellarmaster is responsible for among other things, ensuring the beer is clear, properly carbonated, and has lost the unpleasant odors associated with young beer. The final step is to drive a tap into the keystone, a small hole on one of the heads and fitted with a brass bushing (Bush, 1997). A minimum of one day settling is required to ensure that the tapping did not disturb too much yeast. In order to vent the cask for serving, the hard spile is removed. The ale will have a fairly low CO2 content, 1.2-1.8 volumes of CO2, compared with “normal” ales and lagers that are conditioned to about 2.5 volumes. For comparison purposes, the solubility of CO2 at 12 ° C in beer is 1.12 volumes (Sutula 1999, pp 161).
Since extraneous CO2 cannot per definition be used, the ale is forced out upon tapping using a beer engine, a piston valve assembly at the bar with a lever attached. It is typically adjusted so that one pull on the handle delivers a half pint. The addition of air is an integral and calculated part of serving cask ales. As ale is drawn out, it is replaced by air through the soft spile. The handles themselves are prominent symbols of an establishment serving cask ale. It is also possible to use a gravity dispense i.e. the ale is poured out directly from the cask which is located somewhere behind the bar. Such a dispense should have a cooling system associated with it due to the higher temperatures of the bar.
Nowadays, due to lack of quality control outside the brewery and the inexperience of modern pub employees, many real ale breweries condition casks themselves. This is also done to facilitate handling for customers. Brewery conditioned real ale is delivered by distributors in casks ready to dispense, and bartenders simply hook them up and pour them without having to worry about the complicated process of stillaging.
This does, however, require some extra equipment such as special casks with gas venting valves to replace the spile system, and a way to remove the layer of sediment before transport to the pub (Cantwell, et al., 1993).
Real Ale is not filtered or pasteurized, it is a “living” beer that retains all of its flavor, and the combination of moderate cellar temperature, low gas levels, oxygen and nitrogen (air) effects, fermentation by-products, and often a “snappy” (due to green beer constituents) hoppy aroma and flavor, means the ale tastes full of character and leaves an impression of a silky smoothness which heightens mouth feel and draws attention to the many layers of flavors (Foster, pp 69). These variables also cause cask ales to have a diverse, non-standardized flavor profile that differs from day to day, if not hour to hour. This is the time honored method of preparing ale. British purists consider this, ale at its best.
Production of Cask Conditioned Ale – A Case Study.
An excellent case study from the Pike Place Brewery in Seattle, USA (Cantwell, et al., 1993) provides insight into the intricacies of cask ale production. The brewery was founded in 1989 with the objective of creating British style ales using traditional methods and the finest ingredients.
Of interest was the intentional choice of inhomogeneous English floor malt varieties. High enzyme, well modified, American and Canadian two-row Barley malt were purposely left out. The inhomogeneous floor malt led to more complex flavor profiles according to the study.
Northwest Clusters hops were selected for bittering hops and a mixture of regional and English East Kent Goldings were chosen for finishing. Too large an amount of dry hopping imparted a “tinny” or oxidized flavor to the ale so that as little as 11mg per 29L (i.e. ¼ barrel) was used. It was noted that air in the cask (upon tapping) allowed the contribution of the hops to soften along with other flavors in the beer.
An interesting quote on the effects of air noted: “…just as air causes a robust wine to open up and become more accessible to the palate, air blends with cask beer to complete conditioning and to soften and generally bring forward flavors that might otherwise be indiscernible. Our cask ales are best about 24h after they are tapped and the air has become part of the beer. It takes confidence to fly in the face of modern practice and allow one’s hard-won beer to be influenced by Oxygen, but the results can be truly wonderful.”
On yeast selection, the strain chosen was extremely flocculent, causing the beers to “fall bright” (Traditional British term for precipitation) quite easily and therefore negate the need for finings. This process took 5-10 days, during which time the casks remained undisturbed.
Priming was done by kräusening with actively fermenting beer (1L of 10°Plato green beer per quarter barrel, approx. 29L, of beer at terminal gravity.) Previously, the brewers had tried using dry malt or unfermented wort, which led to insufficient conditioning i.e. not enough yeast cells. The brewers then tried racking several specific gravity points earlier than terminal gravity, however this led to the opposite effect, and too much yeast remained in solution.
Production of Cask Conditioned Ale – Continued
While some of the bigger breweries use enclosed cylindrical conical tanks, the traditional English method uses open primary fermenters designed to allow kräusen to overflow into a collection area. There, it is either removed or allowed to return into the main fermenter. This technique tends to introduce added oxygen to the fermenter that often results in slightly elevated diacetyl levels in the beer (Bush, 1997.) This however, is not necessarily an off flavor as long as it is not overpowering. Also, the secondary fermentation reabsorbs some of the diacetyl.
Primary fermentation is usually complete within 5-7 days at approx. 16°C-20°C as with most top fermented yeast strains. Exceeding these temps will increase bouquet compound concentrations and the ale will have excessively fruity and harsh overtones. It will also increase diacetyl production. The ale is racked into casks when approximately 1° Plato of residual extract is left with yeast cell levels of 0.25-2 million yeast cells per ml of ale (Bush, 1997).
For low original gravity ales such as Mild Ale (where there is little residual sugar left to ferment), it is essential to prime the cask with additional fermentable material to ensure carbonation. Although the case study detailed above documented kräusening as the priming method of choice, it is more common (at least in England) to use simple sugars for priming. Chief among these are white cane or beet sugar followed by invert sugar (a Glucose:Fructose mixture). All of these sugars are fully fermentable (Sutula 1999, pp 160-163).
Determining the amount of priming sugar is a function of initial and desired volumes of CO2 and the fact that 4g of sucrose per L of 1° Plato green beer yields approximately 1 volume of CO2. Using the assumption that the green beer at the end of primary fermentation is saturated with CO2, one can use a solubility chart to find the amount of dissolved CO2 and compare with how much is desired upon tapping. The difference is multiplied by the above conversion factor to obtain the amount of sugar to add (Sutula 1999, pp 160-163).
Isinglass fining quantities range between 1-5 L per imperial barrel (4 firkins or approx. 164L.) Isinglass is composed of collagen molecules which carry an overall positive charge. Since yeast and other haze particles (proteins, polyphenols, etc.) have an overall negative charge, electrostatic attraction leads to aggregation followed by sedimentation (Bush, 1997.)
Batch size should also be considered since a high turnover rate (depending on the ale style, anywhere from 3 to a maximum of 7 days) is required due to the instability of the ale. For successful turnaround, Nemeth reports “the minimum amount of beer required to make cask conditioning work is 1350 U.S. gallons (i.e. approx 51 HL).”
Serving Cask Conditioned Ale
The method of serving cask ale has a direct influence on the taste of the brew and as such merits attention. Serving ale through any hand pump agitates the beer and aerates it. One such system, the sparkler, deliberately maximizes this agitation. The sparkler is a tight nozzle with small holes, normally at the end of a long “swan neck” tube, through which beer is forced, often requiring several strokes on the hand pump. This agitation produces a thick creamy head; it also removes much of the natural carbonation from the body of the beer, and drives much of the hops bitterness into the head of the pint. Also, the thick creamy head supposedly blocks aromas from the beer itself. Such a pint is traditional in some parts of the North, and beers are brewed there with this in mind. However, used on other beers it leads to a different flavor balance from that intended by the brewer (CAMRA)(Daniels 1996, pp 159).
The choice to serve cask ale on a regular basis is not a simple task. It takes considerably more commitment on the part of an establishment when compared to “keg” beers for all the reasons discussed above.
In recent years, consumption of cask ale has been dramatically declining. The boom of the 90´s seems to be over. One possible reason is the rise of “nitrokegs”. These are beers that combine some of the mouth feel properties and flavor of cask ales, with all the advantages of kegs and none of the disadvantages of casks. This is done by dispensing with a Nitrogen/CO2 mix and using sparklers. Another reason is the stocking of cask ale in unsuitable establishments. Not every establishment has the commitment required in dispensing cask ale. One of the worst things that can happen is for an establishment to serve cask ale but without investing the extra time and effort needed. The end result is a poor if not downright undrinkable pint with ensuing bad publicity regarding cask ales. Cask ale brewers should therefore, in the interest of self preservation, be very selective when choosing outlets.
In conclusion, a brief foray into Cask conditioned ale was presented. A history of the Ale genre and the intricacies involved in producing and serving this style have, it is hoped, proved the validity of this style as part of world beer culture. Understanding cask conditioned ale serves to further enlighten brewers and connoisseurs alike with the end result being, hopefully, good beer.
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