Sorry to harp on this, but there's a definite reference in the
quote from Kent Fletcher I posted above where he describes beer filtered through a 1-2 micron filter as tasting like 'seltzer'. A quick Google finds a sort-of one from
Jim Busch (of Victory) here.
I don't have it in front of me but I'm pretty sure Miller recommends a 4 micron filter as a commercial practice... even though he says filtering (with no specifics on pore size) will strip the beer of flavour and body earlier in the book!
But there's a fantastic explanation of all this stuff
here which comes to the conclusion that:
So if you were to say exactly what you said above, except substituting "1 micron" for "5 micron" I may well have believed you.
Interesting links Mal - I've read your links & can't find anything there against 1 micron filtering (though couldn't find the "seltzer" comment) - Most of the comments are of a "I've heard that" nature & i see no scientific or personal fact to back it up. I'm not saying there isn't, just not in what I read in those links. Also if you read some of the other posts in those links, there are some big raps for filtering "
"From: Jim Cave <CAVE at PSC.ORG>
Subject: Filtration
There has been some limited dialogue on the digest lately
about the relative advantages/disadvantages about filtering beers.
I regularly filter some of my beers, depending how quickly I use
them, how much time I have and for what purpose they will be used.
I have also been able to compare various beers which have been
filtered with unfiltered "control kegs" from the same batches.
Invariably, I have found that filtered beers have a cleaner, more
professional quality and are brilliantly clear, however, these beers
are less stable, the latter feature I believe due to a couple of
aspects of home filtration systems.
I think I remember that I read in Dave Miller's book on
Pilsners, that this type of beer benefits from filtration, by
removing "green beer" qualities. However, he notes that the life
of the beer is reduced by stripping the beer of it's yeast. I
concur with this. I find that a home-filtered pilsner that has
been kept at serving temperature noticeably deteriorates after
about a month to 6 weeks, depending on how much is left in the keg."
So he's saying that D Miller says filtering benefits Pilsners!
Like Jim I've actually made many beers done both ways & my personal preference is filtering.
Finally, (below) again from your links - this research seems to suggest that even a 0.2 micron filter isn't capable of stripping desired quality's yet there is anecdotal evidence that maybe it does. I personally don't like to sterile filter, hence the 1 micron - 5 micron in my experience still leaves a slightly hazy beer, tried & tested.
"The good people at Amicon Tech. (thanks for your research John Carpenter)
say that
> Their 10,000 MWCO(molecular weight cutoff)
>membrane is 10 Angstroms, the 100,000 MWCO is 100 Angstroms....she said
>1 million = 1000 Angstroms or 0.1 microns, and she thought the
>relationship was linear. So.... 10 million MWCO is 1 micron. A 5 micron
>filter would only filter out globular proteins with molecular weights of
>greater than 50 million. That's a pretty big protein, <SNIP>
>about 7-10 microns. So my conclusion is you can filter your beer through a
>5 micron filter and remove the yeast and any remaining trub and not have
>to worry about filtering out any of the other "flavor" proteins.
The *most* haze forming proteins are of the order of 50,000 plus. The
"MMWP's" of brewing are of the order of 5,000-50,000. These are the
mouthfeel and head retaining proteins, although they overlap with haze
forming ones. Proteins greater than 1,000,000 (HMWP) have no chance of
surviving a 60 minute boil and end up in the trub. (One reason for a 58-60C
rest is to reduce these HWMPs to Medium Weights that could survive the
boil.) Thus with a 5 micron filter, *all* soluble beer protein should pass
through except for "protein binding" to the filter medium itself. (As Chuck
Burkins pointed out.) Some yeast would also get through 5 microns.
>From Amicon's info above, a 2 micron or even 0.2 micron filter would also
not seem to be a problem. However 0.2 micron sterile filtrations in
breweries reportedly give a thinner mouthfeel although Amicon says molecular
weights as high as 1,000,000 should sail through? Something doesn't gel
here? I will research this further unless someone has data."
There are plenty of pro filtering comments as there are anti filtering comments, I think it pays to trial yourself & then make your own assessment.
I'd be interested in hearing from those that have started filtering & disliked what it does to their beer, so have stopped - I'd be amazed if there's more than a couple & I've sold hundred's of units.
Cheers Ross