ALE Summer 1997 No. 288

Back to Basics - Putting on the Pressure

By Paul Ainsworth

In the last issue we looked at keg beer, which CAMRA considers hugely inferior to cask-conditioned beer. But is all cask beer real ale? Sadly, the answer is no.

The key phrase in what follows is "applied gas". When cask beer is delivered to the pub cellar, it is, unlike keg, a living thing with yeast continuing to ferment and "condition" the beer. In doing so, it produces carbon dioxide and it is this gas, dissolved in the beer, which prevents it being flat and lifeless. The cellarman's task, by careful venting, is to keep a natural level of gas in the cask, but without any excess building up, which would make the beer fizzy.

As beer is drawn off, air enters and progressively dilutes the natural carbon dioxide. Eventually the oxygen in the air will damage the beer by encouraging bacterial growth. The end result is the vinegary pint we all know and hate. However, as long as the beer is sold relatively quickly and the cellarman knows his job, such problems need never arise.

Beer to make your teeth tingle and fur up your mouth...

Back in the sixties and seventies, when cellarmanship standards were generally lower, many breweries hit on a weeze for extending the life of cask beer. By feeding additional carbon dioxide into the cask, oxygen is prevented from coming into contact with the beer and so it lasts longer. Unfortunately the unnaturally high level of carbon dioxide leads to the beer becoming fizzy and over-conditioned. This did not worry the accountants and marketing men who had ousted the brewers as top dogs in the breweries.

At the time CAMRA started, nearly all local Greene King and Tolly pubs employed this system, known as "top pressure". In Greene King pubs the immediate give-away was the use of white mini handpulls which acted as switches for the dispense spout. Thankfully, most pubs have thrown out the top pressure system, though a handful remain.

Less tingle and less furring-up, but is it natural?...

A much more controversial mechanism for keeping oxygen away from beer is the cask breather or aspirator. This works by keeping the gas in the cask at atmospheric pressure by either admitting applied gas to replace beer drawn off or venting any excess gas generated by the beer itself. The carbonation level of the beer is thus kept constant.

The effect of the breather on the taste of the beer is a matter of hot debate. In controlled tests, most drinkers have been unable to distinguish between naturally conditioned and cask breather beers. However there are very good reasons why CAMRA totally disapproves of these devices.

It's not natural. It is unnecessary.

Firstly, the whole point of the breather is to extend the life of the beer beyond the standard three days. This it will do but at a cost in quality terms; flavour changes such as reduced sweetness and loss of hop character are likely to occur, while the flavour effects of carbonation itself will start to take over.

Secondly, having this life-support system on hand often tempts licensees to extend their range of beers. The result, all too often, is six or seven beers in average to poor condition, rather than a couple which are tip-top.

Thirdly the cask breather represents the thin end of the wedge. If CAMRA were to approve such a device, which works by applying gas, it would be difficult to argue against the use of top pressure which does the same, only more so.

For these reasons, CAMRA's recent AGM agreed that in future any pub which uses a cask breather on any of its beers cannot be entered in the Good Beer Guide.

Applied gas isn't the answer to good beer. To achieve that you just need to sell the appropriate number of beers in the right size of cask and apply just one thing basic standards of cellarmanship.

Next in the Back to Basics series...

ALE Summer 1997 No. 288 : Next section
Cambridge & District CAMRA