FROM WATER TO WINE AND BACK - A FILTRATION PRIMER

Well howdy there, Pardner,

If you’ve ever experienced the incredible disappointment of homebrewing, in particular brewing your first batch of beer without professional help, you might be tempted to conclude, on comparing your swill with the professionally made stuff, that brewing is hard. I’d offer a counter-hypothesis: brewing is super, super easy; it’s making beer on par with modern, professionally-brewed beer that’s the herculean task.

There are a number of reasons for this, and there are certainly plenty of styles that can take a beating (and are thus a closer competition between the home-made and “real” stuff), but as regards presentation, there’s one immediate difference between the two groups: professionally brewed beers are by and large crystal clear, and homebrewed beers are almost entirely on the scale of Ziplock plastic to mist-fogged mirror.

Beyond the aesthetic concern, which has been around for a while (remember that post?), there are a few practical concerns regarding imperfectly clear beer: hazier beers tend to have shorter shelf lives, which is especially significant for distributed beers (read: six-packs from your neighborhood bottle shop), and depending on the nature of the source of the haze, they may not taste as good as “brilliant” (super-clear) versions, with yeast and hop matter suspended in hazy beers being particularly responsible for lackluster flavor where their presence isn’t expected (Hefeweizen, for example, is a classically hazy beer, in part due to protein-based haze, but also potentially due to suspended yeast, and that flavor is a virtual requirement).

So, what exactly are we filtering out of beer, and how might we actually filter our beer, whether our budget is six figures or three?

What are we filtering

In theory, in our brewing setup at least, an object as big as, say, a marble might be able to make it from the boil kettle to the fermenter, but there are tons of checks and balances that limit the size of items that make it into fermenters. 

First, you have the mash, wherein the water and malt are mixed and some enzymatic magic happens. In the olden days, this mixture might actually be the very slurry that you ferment and then drink, but in modern breweries, at the end of the mash, you recirculate the “wort” (liquid) through the grain bed until the liquid that passes through is clear, and then you pump it into the boil kettle, in effect using the grain bed as a giant filter. This stops anything above the size of a piece of barley from getting through - think, a sand-sized piece of malt, say.

Then you have the boil, where you’ll be adding the hops and perhaps some chemicals, but little else most of the time. Interestingly, the boil kettle would never have let too many hops into the next stage, since in the olden days, they used whole hop flowers (roughly the size of a chestnut when fully hydrated) which were easily filtered out by a hopjack (don’t ask), and nowadays, we have hop pellets which produce a fine sort of paste of hop matter, but which is effectively separated out via whirlpooling.

Finally, you pump this wort into fermenters, and add yeast (an obvious thing you’ll have to remove later), as well as dry hops in some cases, most often in the form of pellet hops (giving you that hop slurry to deal with). You might also add whole fruit or spices, potentially, but purees and extracts are largely taking over in the brewing industry due to, you know, this exact thing we’re talking about.

You might ask, then, if there’s anything microscopic that we have to worry about, and the answer is definitively yes, if we’re brewing with protein-heavy malts (or oats, etc.), or if our brewing practices aren’t great (i.e. we’re not achieving clean hot and cold “breaks”, i.e. not knocking enough malt protein out of solution).

Which is to say, the primary articles of filtration are yeast, hops, and proteins. The former are on the order of a few microns (a thousandth of a millimeter; hair bottoms out around 20 µm - microns, micrometers - in thickness), hop particles might be, oh, 5-1,000 microns I’d wager, and break proteins range from .5 µm to 80 µm.

How the big boys do it

There are plenty of commercial solutions to this modern problem, and, as I so often do, I think the cleanest way to present them is in bullet-point form, like so:

• Time and Gravity

  • The oldest method is still very effective, the question is merely “how long is this going to take.” Traditionally-fermented lagers may be acceptably clear at the end of their, oh, nine week fermentation, but an extra few weeks will certainly help

  • While yeast does quite well at dropping out of beer when said beer is chilled to around freezing, and when there’s enough calcium in solution, beers with protein-driven haze may take an impractically long time to clear, though theoretically they should eventually clear

  • Worth noting: this step can be done in ale casks, say, as they sit and prime or wait for an open tap, though we do use Biofine, a vegan and entirely food safe clarifying agent, in our casks

• Physical filters

  • There’s a pretty surprising array of filter options, but the idea is the same: pass the beer through some sort of paper or cloth, or even through a murky bed composed of beer and diatomaceous earth (which is what we use - that, and I think a leaf filter), et voila - clean beer

• Less time and “gravity”

  • F = ma, so why not just jack up the a? By spinning beer very quickly in a continuous centrifuge, and thus subjecting it to many times the force of gravity, you can essentially speed up the natural clarification process (natural here simply meaning old and filterless) and get clear beer quickly

  • An insane bonus I just learned about is the fact that with these, you can apparently tune the level of filtration you’d like, allowing you to pull yeast and hop particulate out of Hazy IPAs without losing the haze - wild!

  • They’re pretty fiendishly expensive though, hence their sporadic use in small breweries, though their yield is about 95%, vs about 90% for a nice lenticular filter (a type of physical filter), which adds up real fast

• Chemicals

  • If you’re okay with merely “pretty darned good” clarity, you can use a number of (totally food safe) chemicals to do this. The trick is basically to dump fairly large (on a molecular scale) particles with a positive or negative charge into your beer, which then glob onto smaller particles and drag them down. Thanks to Stokes’ Law, we know that these clumps will drop out proportional to their radii squared, so by doubling the radius of these globs, their terminal velocity (maximum falling speed) is four times greater. Any physics majors out there? No? Okay, sorry.

One more thing: every single one of these options is available on a homebrewing scale, even the centrifuge, which is nuts.

Conclusion

Clarifying beer used to be either an alien concept, or else a fairly straightforward and natural consequence of lengthy aging in caves, but in this crazy new world of readily accessible glassware, we’re stuck with rapidly clarified beer, and I hope this information has been interesting from at least a “how the sausage is made” perspective. And I guess it’s time for MacLeod to get a ‘fuge!

Cheers,

Adrian “Tempus ‘Fuge It” Febre