Friday, 16 October 2009

Question for lager experts

Go to any German or Czech brewpub and one of their chief offerings will almost certainly be one or more unfiltered lagers. They are often quite murky. I don't mind that if it tastes good and you can still see through it. I do draw the line at thick yeasty soup.

Something I have been wondering for a while is why lager apparently needs to be filtered to get it clear. Real ale usually drops bright after just a few weeks, so why does lager still have to be filtered after weeks or months of cold conditioning?


  1. Hmmm... good question. Never thought about it really.

    I've had a few unfiltered lagers where the yeast had settled and they weren't murky, but it was exceptional.

    Might it be the dispensing method with top pressure? On the other hand, when you are at a brewery and you are given a beer tapped straight from the lagering tanks, it's also murky. Might it be because the lager yeasts are still floating around? Dunno...

  2. Probably something to do with flocculating and non flocculating yeasts, but I'm no expert in this aspect.

    Unfiltered lager is generally shite.

  3. It has nothing to do with the dispense method and all around the flocculation characteristics of the yeast.

    Most ale yeasts (not all) are good flocculators, meaning the yeast naturally clumps together in the tank. The bigger and heavier the clumps the quicker the yeast drops out of the beer, giving you a bright pint.

    Brewers use all kinds of tricks to try and speed up this flocculation, the most common being the addition of finings, which add charged particles (from a range of things from the swim bladders of fish to plastic dust) to speed up and improve the flocculation of yeast and other particles in beer.

    Generally most lager yeasts (again, not all) are poor flocculators and this is one of the reasons for the long lagering/storing times of upwards of 2 months to get a naturally bright lager.

    This is also why it is common to see horizontal tanks in lager breweries. With the shorter tanks you have less height for the yeast to fall, hopefully speeding up the process.

    No beer needs to be filtered, if the brewer has the time/capacity/money to let Stokes Law do its work.

    Clarity is often just a byproduct of filtering, which is usually more about getting a biologically stable product into a bottle/keg/cask.

  4. Not sure I would agree with you on the unfiltered lager being shite though, I can't think of of a shite unfiltered Czech lager I have had, off the top of my head that is. Perhaps the Czechs do it better?

  5. I think Tandleman is thinking about the identikit helles, dunkles and weizen you tend to get in run-of-the-mill German brewpubs. I doubt that filtering those dull beers would make them any better, though. Mind, I've had some which were okay, and I'd almost always choose to go to a brewpub rather than a Kneipe selling crystal clear Krombacher or Bitburger.

  6. I agree with Al. Czech unfiltered lagers, even macro ones like Budvar or PU are really, really good. Have a pint of those (or any) tapped straight from the lagering tank and you'll believe in God once again (at least until you finish the glass)

  7. Thanks for the very informative comment, Jeff.

    On the subject of lager, I've heard two people in the last week arguing that proper lager can only be made in open fermenters. What's that about?

  8. Real ale usually drops bright after just a few weeks
    Hopefully it drops bright after a few days, not weeks, but that is usually due to the use of finings.

  9. In my experience (brewing lager on a microbrew scale on & off since 2000) as Jeff from Lovibond's says above, lager yeasts in general seem not to floc out very quickly.

    Craft-brewing lager includes a lagering period - in addition to helping to round out the flavours in maturation, this also settles out yeast & other haze-forming particles.

    We found that we had pretty clear lager after about 3 weeks cold-conditioning, but the beer flavour improved with further time at c0degC.

    We then put the beer straight into cask - we added finings to ensure "star brightness" but it probably would have been clear enough without it.

  10. Curmudgeon, I meant dropping bright from the start of fermentation, not from when it arrives at the pub.