Warm, Flat, and Delicious: A Primer on Cask Ale

Perhaps you’ve seen it at your local watering hole, at the end of a long line of colorful, gimmicky tap handles. It sits alone, in a corner, often barely visible on the inside corner of the bar: a long curvy brass neck and an old fashioned looking, unadorned wooden handle.

Surely it’s just kitsch, you think. A decorative throwback, reminiscent of the hand-pumped water wells of the frontier days. Then one day an unassuming beer geek wanders in with a notepad, speaks to the barkeep, and you watch him as he wrestles, through sheer brute force, what looks like beer out of that decrepit old device. No, my friends, that’s not decor; it’s called a beer engine, and is home to one of the true gems of the beer world: cask-conditioned ale. Many have seen it, some even know what it is, and yet in America it is a most overlooked and underappreciated piece of beer culture. That’s why I’ve chosen to try my hand at convincing a skeptical public why they would ever want to drink warm, flat beer.

Cask-conditioned ales, based on a loose interpretation of the definition offered by the Campaign for Real Ales (CAMRA) in the UK, has two primary characteristics: it has been naturally conditioned by the action of yeast, and has not been pasteurized or filtered. Let’s compare this to two more familiar data points to see what makes cask-conditioned ale so different.

Typical tap or keg ale is filtered to remove yeast and other sediment, giving it more of a crystal clear appearance and better shelf stability. You see, many of the compounds that are removed by filtration would otherwise decompose and undergo reactions over time that can degrade – or sometimes improve – the flavor of the beer as it ages. Inconsistency is the bane of the commercial brewery, and over time the commercial brewers have had a great deal of influence on consumers’ tastes and preferences, even among craft beer drinkers to a lesser extent.

Shelf stability is further improved by pastuerization, which kills off any microorganisms that might still exist in the beer at the end of fermentation. This keeps infections from wild yeast or bacteria from impacting the flavor stability over time, but it also eliminates any yeast still suspended in the beer that hasn’t flocculated (i.e. went to sleep on the bottom of the fermenter when it ran out of food). This makes bottle or cask-conditioning the beer impossible, and so it is force carbonated by pressurized carbon dioxide. That is, the brewers place the beer in a keg or tank and applies high pressure CO2 until the gas dissolves into the beer, giving it carbonation, then the full and carbonated keg, bottle, or can is sealed tight to keep the carbon dioxide from escaping until the beer is served to the consumer.

Then there’s lagers. These too are mostly pasteurized, filtered, and force carbonated, but only after a secondary fermentation and lagering period. After primary fermentation is complete (or nearly complete) the beer is stored for a long period of time at a low temperature, and the yeast clean up a lot of the mess they’ve left behind during primary fermentation. Things like esters, phenols, and higher alcohols that contribute yeast based complexity to some ales but are unwelcome in most clean-drinking lagers.

So what makes Cask Ale different? First of all, it’s alive. The beer is not pasteurized or filtered in any way, the brewer simply adds fining agents to it that encourage the yeast and other sediment to sink to the bottom of the cask so that it doesn’t end up in your glass. But the yeast is still there, and still actively working in the bottom of the tank, imparting flavors to the beer that lies above it. The beer is, in fact, fermenting while it is being served. This secondary fermentation is different from that undertaken by lagers because it doesn’t take place over a long period or at low temperature. The goal is the production of carbon dioxide which is trapped in the cask and naturally carbonates the beer. Another goal is the continued production of yeast byproducts such as esters, phenols, and higher alcohols – the yeast is not cleaning up after itself like it would during lagering, since there is still enough sugars to continue eating. The yeast actually continues to make a mess of the beer. That mess, however, lends a greater complexity to the beer.

Next is the carbonation. As the beer conditions inside the cask, a cellar master can control the level of carbonation by using corks of varying density in one of the holes on the cask (shown sticking out of the top of the casks pictured above). A denser cork allows less of the carbonation to escape and will result in a more heavily carbonated beer, where as a lighter cork allows more to escape, resulting in flatter beer. But since the beer is served through a beer engine (and your barkeep’s own elbow grease) rather than being forced through the tap lines by high CO2 pressure, and because the beer is naturally carbonated rather than by force carbonation at high pressure, the beer tends to be noticeably flatter than tap beer.

Why on earth drink flat beer? Most of us have, at one time or another, thrown a kegger and had some beer left over the next day. We know that this flat, oxidated beer is inferior to the beer we had the night before. Those of us who were in college at the time probably drank the beer anyway because beer money was too hard to come by in those days. But the reason this beer tasted so bad (aside from oxidation) was that it was designed to be served under heavily carbonated conditions – most of the popular frat house beers in this country are. They are bland, and nearly flavorless, and simply don’t taste good without the crisp bite you get from forced carbonation. You see, higher carbonation distracts the taste buds from tasting the complexity in beer; bubbles coat the tongue, separating the beer from your taste buds, and the carbonation raises the acidity of the beer, creating the only real balance in frat house beers, since many of them use hops extremely sparingly. High carbonation reduces your ability to taste complexities in the beer, which makes it a good thing only if the beer has no complexity to begin. The fizzy yellow lagers of my youth had none; the craft beers I enjoy today do.

There is one tradeoff to this lower carbonation rate, however. Carbon dioxide dissolved in the beer under pressure begins to be released when the beer is served, bubbling up to the top and out of the beer completely. In the process it drives with it a multitude of aroma compounds, for example the volatile compounds found in hop oils. This means that without a high carbonation rate, there is no rush of gas escaping when the beer is served, and the nose will be far less potent. On the other hand, this also means that the aromatics aren’t escaping into the atmosphere; they stay in your glass for the most part until they find their way to your belly. This is why, in my opinion, the best cask ales are IPAs and other heavily hopped beers. Not only do they have enough potency in the nose to still shine when served with low carbonation, but cask-conditioning and proper serving really helps the delicate and volatile hop compounds come into their own. In this Punk’s opinion, there is no greater pleasure in the beer world than a properly poured pint of cask-conditioned IPA (until recently my beloved local, the Sunset Grill and Tap, had a Dogfish Head 60 Minute that would nearly bring me to tears every time I had it…I miss it terribly).

Then there’s the temperature. The proper serving temperature of cask ale (often referred to as cellar temperature because traditionally the casks were kept in cool cellars below ground, before the age of refrigeration) is 54-57 F. Refrigerator temperature, where most beers are served, is typically around of 40 F, and room temperature is about 70 F. This means that these beers are meant to be served fairly warm – certainly cool rather than chilled – another forbidden act for the average fizzy yellow beer drinker. (Author’s note: I have been known to drink good quality lagers, especially darker ones such as Bocks and Dunkels, at cellar temp all the same, because I feel they deserve it; it really gives their malty complexity a chance to shine. In fact I’ve been known to drink good quality ales at nearly room temperature. It’s not for everyone, but hopefully after reading this you might understand why I would do such a thing.)

Again, the reason this higher temperature works is the differences between craft ales and fizzy yellow lagers. Cold has a tendency to numb the sense of taste so that it obscures some of the complexities of a good beer. Again, if a beer has no complexity, this works in its favor. Think about that the next time a beer commercial touts its product as “frost brewed” or accentuates the cold refreshing aspects of it, or tries to associate itself with snow covered mountains and brisk mountain streams. What exactly do they have to hide?

Furthermore, warmth excites the volatile compounds we spoke of earlier, so that the drinker of a properly served cask beer gets a slightly more aggressive aroma from the beer, whereas chilled beer tends to reign in the release of volatile compounds.

There’s one more thing conspicuously missing from a cask-conditioned beer that is off-putting for some drinkers: a nice frothy head. There is great debate in the world of cask ales about the use of special taps and other methods to coax some frothiness out of cask ale, and we’ll get into that in another article. The simple fact though, is that cask beers in general will not achieve the kind of head that is expected on a tap beer.

Head forms in tap beer when the carbon dioxide comes out of solution and bubbles to the top of the glass. The bubbles surrounding the escaping gas are made of various proteins and other compounds that are pulled out of solution along with the CO2. Think of this as a less invasive form of filtration; whenever you pull these compounds out of the beer and into the head, you disturb the balance of the beer and potentially rob it of some complexity. Again, fine if the beer has no complexity, but a nice cask ale can really show its chops when served without a head.

The reason tap beer has such a vigorous and lingering head is that it is continually replenished for a while after the beer is poured, as more and more CO2 comes out of solution and drags precious hop oils with it. The only way to accomplish a head like this on a beer that is not force carbonated is to agitate it as it goes through the line or the spout between the cask and the glass, or to hold the glass below the tap and let the beer be agitated as it falls into it (not unlike the way frothy “pulled tea” is served in east Asian cultures). But since there’s not enough carbon dioxide dissolved in a cask ale to continue to feed the head, this head will die down shortly, and will have robbed the beer of some of the more delicate and volatile flavor compounds. Depending on how the recipe was formulated, this might be OK (hence the debate I alluded to) but if the recipe is meant to be served without a frothy pseudo-head, why sacrifice flavor for the sake of eye candy? Does anyone out there really like the taste of a beer’s head? Judge a beer by the taste, not according to what beer commercials condition us to think it should look like.

Now I’m not saying that cask-conditioned ales are plug-and-play for the average beer consumer. They’re a lot like certain Belgian beers, it’s something a little odd and funky you might have to work your way up to over time. Even now, I often find it takes a few moments for me to adjust my expectations and my palate to really get the best out of a cask ale, especially if I’ve been drinking tap beers beforehand. But if you’ve been on a brewery tour and had a chance to try “green beer” that isn’t done conditioning, or if you love hoppy beers, cask ales are definitely worth a look. Just know that the quality varies widely based on the serving conditions maintained by the barkeep, so try asking for a sample before you order a full pint, especially until you get comfortable with cask ale’s unique characteristics and the reputation of the purveyors you frequent. Furthermore, try asking a beer guy like me for a recommendation where to find a good one (in good old Beantown, I’m a huge fan of the Sunset as I said, but stay away from John Harvard’s Brewhouse! they serve it way too cold). In fact, take a beer guy with you so they can confirm or deny the quality and authenticity of the particular specimen in realtime.

But in the unlikely event you can’t find a beer guy near you, just know that these gems are worth looking for, even with their variable quality, and don’t let your preconceived notions about warm, flat beer stop you from enjoying one of life’s greatest pleasures.

This was just an overview; we’ll return to the topic of cask-conditioned ales in the weeks and months to come, since there’s a lot of ground to cover here about the different ways they are kept and served, the history and culture behind them, and the modern efforts to save them. Stay tuned.


Geek Speak Decoded: IBUs, Hops, and Bitterness

This is the first in a series of articles on technical topics that might be of interest to the average craft beer consumer. They will cover topics that are on the minds of brewers when they design brews, but will be fairly non-technical and give only the essentials to help our readers better understand and appreciate the beer they drink, and decode any craft beer marketing material that they might come across.

By now, anyone who’s been to a respectable beer bar and tried to order an IPA has surely heard of IBUs, and might even be aware of a link between this number (a measurement of bitterness) and how much hops the brewer used. But there’s much more to consider here that gets lost on most drinkers.

Indulge me for a second with a geeky analogy from another realm. The situation with IBUs reminds me of a similar one a few years ago in the chip wars between Intel and AMD. Chips used to be marketed by their clockspeed in GHz. This gave the consumer a nice, simple way to compare the performance of two chips or the PCs running them without having to be a computer engineer or understand the underlying architectures. It was a very convenient tool for consumers and was widely exploited by manufacturers.

The problem was that the number by itself was useless; Intel figured out how to increase their chip’s clock speed by doing less work per clock tick (and thereby generating less heat and allowing them to run “quicker”). The result was that an AMD chip had better technology and would outperform an Intel chip with the same GHz number on it. But they were also more expensive and because the numbers were the same, consumers would pick the cheaper Intel chip, never fully understanding the real issues affecting performance. This led to a really ugly situation where AMD started using their own proprietary (and subjective) numbering schemes that didn’t really allow the consumer to casually compare performance at all. Thus the irresponsible use of this number as a marketing tool rendered it utterly useless to consumers. I fear the same thing might be starting to taking place as we speak in the crowded world of IPAs and other highly hopped beers.

IBU stands for International Bittering Unit, and is a measure of how much hop bitterness is present in a beer. The craft beer market in the US caters to a rebellious lot of consumers that are shunning the characteristics of mass-produced fizzy yellow lagers, particularly by actively seeking intensely flavored and highly hopped beers. The IBU has become the latest tool in the craft beer marketer’s kit, letting drinkers see at a glance which IPA is most intense and hoppy, and therefore better… but this number alone can’t tell you that, and it’s important for consumers to understand why.

First, one pivotal key to brewing a good beer is balance. An intensely hopped, bitter IPA is not going to taste right if this bitterness is not balanced by malty sweetness. There’s a simple rule of thumb for calculating how balanced a beer is, using a value known as the BU/GU ratio, which I will cover more completely in a later article. Essentially it is Bittering Units (IBUs) divided by Gravity Units, which is a measure of how much residual sugar is left dissolved in the beer after fermentation, the rest having been converted to alcohol. (Brewers typically use the original gravity, i.e. before fermentation takes place, in the BU/GU calculation, but it is still a decent proxy for the residual sweetness since attenuation-the portion of available sugar fermented-of most yeast strains typcially doesn’t vary enough to throw off the results.)

Even understanding this simple ratio does little to help the consumer, however, as the gravity figures are not touted as frequently as the IBUs. Even if you used alcohol content as a proxy for original gravity (which is feasible but troublesome for the same reason OG doesn’t correspond perfectly to residual sweetness), there are many other factors that can affect the percieved balance of a beer.

The second issue with the IBU rating has to do with the chemical reactions that take place during the boil. Hops contain many chemical compounds that affect the character of beer, but for our purposes we’ll focus on two groups: alpha acids and hop oil compounds. As the hops stew in the boiling wort, two things happen: alpha acids undergo a chemical reaction known as isomerization, which produces the bitterness that hops are known for. The other is that the volatile compounds in hop oils, which provide a rich tapestry of flavor and aroma to the finished beer, are slowly boiled away and lost forever. Therefore, hops that are added near the end of the boil (or even after the boil in a hopback or during conditioning in a process called dry hopping) will impart more flavor and aroma to the brew since the compounds don’t boil off, but will add much less in the way of bitterness (i.e. lower IBUs).

So what does it all mean? Higher IBUs do not indicate a better beer, by any stretch of the imagination. They measure bitterness, but say nothing about balance. Furthermore, bitterness comes from hops, but unscrupulous brewers can goose their IBU numbers and attract more attention by boiling all of the delicate hop oil flavor out of their hops to extract the maximum bitterness. Just be aware of this the next time you belly up to the bar for an IPA and are greeted by the “convenience” of having IBU numbers in front of you. Judge beers by taste, not by numbers.