I really like cask beer, even more than my own home brew. Everyone has their own tastes of course, but here are some of the reasons why I think cask conditioned beer is a thoroughly good thing.
Actually, I realise writing this that they are also very likely the points that might turn some people off. I like the fact that its warm and flat. It’s not warm of course, but 12°C –cellar temperature. The glass feels cool to the touch, but not cold. At this temperature, the beer feels cool in the mouth but the flavours really come to the fore. The beer is flat in the sense that, although it does contain carbon dioxide, the CO2 stays in solution in the beer. At 12°C, at atmospheric pressure, 2.1g per litre or about one volume per volume, i.e. a pint of beer has a pint of CO2 in it. To get bubbles in beer, you have to put more CO2 into it than the beer can hold in solution. Except cask beer. Cask beer gets its bubbles when it is pumped up from the cellar and air is drawn into the beer when it is pushed out the tap and this is enough to create a gentle head. The bubbles are bubbles of atmospheric air, so mostly nitrogen. CO2 actually has a definite contribution to beer flavour. When it comes out of solution, it can sweep volatile hop aromas out of the beer with it, meaning if you’re there to smell it, you get a lovely hoppy smell off the beer (The massive amounts of CO2 given off by fermenting beer mean hoppy home brews smell amazing when they’re fermenting). But it prickles the tongue and is ever so slightly acid tasting. Too much CO2 in beer and you don’t taste the other flavours as much. I think the gentle carbonation of cask beer is particularly suited to low ABV beers.
And then there’s social and environmental reasons to like cask beer. 12°C is ambient temperature in the cellar so the beer doesn’t actually require further cooling. Commercial lager, in contrast, is refrigerated during fermentation and subsequent maturation and ‘lagering’, and at the point of serving, so it’s carbon footprint is many times higher. It’s also shipped all over the world. Not that we should onerous carbon footprint calculation every time we decide what to order but it’s something to bear in mind.
Cask beer doesn’t keep for very long. It’s an unfiltered, unpasteurised living product that is still undergoing changes in the cask so the shelf-life on an untapped cask is about one month. Once it is tapped, it lasts only three days. This means it can only really be sustained by a local infrastructure of small or regional breweries supplying their own local area. If you’re a brewery trying to sell internationally, where your beer is completely outside your oversight, you have to pasteurise and filter to give the beer as long a shelf-life as possible. You can of course, pasteurise and filter even if you sell locally. The inference is not, if local, then real; it’s if real, then local. There is some connection the other way too. Real ale requires less initial brewery plant and equipment than bright beer, which makes it easier for small independent breweries to operate. The benefit of lots of small local businesses, of course, is that they create interesting variety. You see this when you go to different parts of the UK. There’s always something you’ve never tasted before.