Filtration of Beer
In Australia and most of the western world the majority of beer has beer filtered for many decades to a crystal clear consistency. The consumer’s expectation was that cloudy beer was thought to be inferior in quality and so demanded clear beer.
However, with the advent of craft beers things are changing. There appears to be a movement to the exact opposite where beers are not filtered at all.
One of the driving forces to this is that it is believed that yeasty beer is far more flavoursome and natural. But is this all that is to the story?
Styles of Beer
The style of beer can dictate whether or not that beer gets filtered. For example a hefeweissen is commonly cloudy by design.But perhaps anyone who has ever tried to filter such a beer will know that this beer tends to be very hard to filter. This is because of the sticky or viscous nature of wheat beers which make them difficult to fine and filter. So perhaps it is a reason brewers decided not to filter such a beer and so the cloudy appearance became synonomous with wheat beers.
On the other hand lagers are by definition clean and crisp in flavour with little overwhelming notes that can come from the yeast left in certain beers. This style of beer works well in the clean, filtered state.
So it is important to realise filtration can serve a useful purpose and so much of the commercially filtered beers tend to be using lager yeasts.
Types of filters
We spoke about diatomaceous earth (D.E.) filtration last week. This is the most complex and difficult type of filtration devised by brewers. However, the result is purely amazing. D.E.is derived from the ground where millions of plankton were fossilised many moons ago. However, it needs to be purified and treated in a special way in order to make it food grade. The diatom, as it is called is a single celled plant.
The diatom consists of fine pores or holes that are so small that they actually trap “chill haze”. So it makes for a very clear beer, so clear that the remaining haze can only be “seen” using an instrument called a haze meter.
Other types of filtration are less obtrusive and hence less clarity can be attained. These include perlite (volcanic rock) which removes yeast and less haze , pad and cartridge filters which can usually remove yeast and beer particles but not haze.
Cartridge filtration is commonly seen in water filtration systems and a similar setup can be used by the homebrewer to remove yeast from beer.
Sterile pad filtration is fine enough to remove bacteria from beer but the yeast and beer particles need to be removed prior to sterile filtration. Sterile filtered beer precludes pasteurisation and so has little effect on flavour when compared to pasteurisation.
In the Masterbrew course students are given the opportunity to taste filtered (using cartridge) versus unfiltered beer in order to see the difference in flavour. Invariably in each class the opinion is usually split ~50:50 as to which one they prefer. If flavour was such a big thing and removal of flavour occured upon filtration the resuls would most likely look much different.
Many microbrewers don’t use filtration systems either due to the fact it is an added cost or perhaps of the mis-information that flavour is lost.
But in reality one should perhaps be guided by the style guidelines (BJCP) and filter accordingly.
But if not filtering beer one must take care not to leave too much yeast in the beer as it can add an unsightly look to the beer especially if poured on tap! And that has a habbit of happenning in the craft brewing industry from time to time.
Another reason we should be concerned about having too much yeast is that there is a more likely chance of getting yeasty, meaty, vegemitey flavours imparted to the beer which is not a good thing in any style of beer!
So filtering beer is recommended for certain types of beer that require clean, crisp flavour but others like wheat beers tends to be a part of the style. So the recommendation is ,”Filter according to style” .
If not filtering, good yeast removal techniques and appropriate equipment is necessary to minimise yeasty beer and reduce the risk of imparting off-flavours.