As above, so below

With the rise of murky craft beer I am once more left thinking how the poor, deluded crafties are groping blindly towards the shining light of our Mother church's teachings. Though in the CAMRA catechism the definition of real ale talks of the inherent evil of extraneous CO2, it is often forgotten that artificial carbonation is also an obvious external sign that the greater evils of filtration and pasteurisation have occurred.

Carbonation itself affects beer flavour, and high levels of carbonation can overpower some flavours, but filtration and pasteurisation are likely to cause more flavour problems. Once beer has been separated from the yeast it has lost a lot of its natural protection from oxidation, and great care has to be taken to prevent off flavours developing. Modern brewers will be looking for oxygen pick up of less than 100 parts per billion, something that is not always possible to achieve. Particularly if you're not working at a megabrewery with high spec. kit. Any problems caused by oxygen will be increased during pasteurisation, and when the beer is then served with a high level of carbonation it is a shadow a what it once was.

The current fashion for beer that can only be described as murky is in part because devotees think they have better flavour, and that they've not been filtered or pasteurised will be a big reason for this.  I myself have seeking out unfiltered and unpasteurised beers for many years. In Britain we have a long tradition of making such beers, and they can usually be found by looking for beers served from handpumps.