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We recently instituted a three-phase filtration process at our brewery. We had occasional issues with varying carbonation levels in bottles from the yeast stuck in sediment, which the filters have definitely solved. However, we have noticed a change in the flavor and aroma of two dry-hopped beers we produce. At QA/QC tastings, samples (stored unrefrigerated in a dark room) from 4 weeks post-bottling are tasting and smelling completely oxidized outside of reason. We have never had storage issues like this before and I was wondering if the filters could possibly be breaking down hop compounds and aiding in premature oxidation? We have not detected this anomaly in any of our non-dry-hopped beers, nor have we detected it in any of our draft beers. For clarification, all product goes through a coarse 7-15um lenticular filter for all FV-BT transfers (post-finings) and only bottled beer goes through a 1um fining and .45um sterile cartridge filter. Has anyone heard of or dealt with this kind of issue before?
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Do you have a method of determining Total Packaged Oxygen at bottling? -
Prior to filtration, are you purging the filter system to remove air (= oxygen), eg. with deaerated water?Comment
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We purge all of the filters with CO2 and keep them under pressure during transfers/packaging. Unfortunately, we don't have anything to test oxygen at packaging, we are fairly small and a little low tech. Our bottling line does perform double evac/purge cycles prior to the pressurized fill.Originally posted by TL Services View PostComment
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really tight filtration
Hey there,
When you say oxidized flavor, you mean that stale cardboard taste? Sometimes oxidation presents in that classic fashion, it can also make strange estery tastes, and other phenolic, band-aid, solventy notes. Not being able to taste the beer, I have a few ideas for you.
For one, .45 um is really tight for beer. Almost all beer yeast would be removed at 1 um nominal provided your filters are intact. I've experienced noticeable flavor and aroma loss from going that tight. I've even seen it change the color!
For two, what kind of pump are you using? Sometimes a microscopic leak in a pump seal will introduce oxygen and with impeller pumps especially it will get beaten into solution and wreak havoc.
For three, depending on your cold-crashing/settling step prior to filtration, you may be able to step up your lenticular module to a 4-6 um (K300 from Pall) or even a K250, and then use your 1 um filter as your final filter. This will give clarity and 95%+ yeast reduction.
For four, you probably already know this but you need to make sure your filter housings are completely full during the filtration run, I like to start everything off nice and slow, gently filling the housings until foam begins to vent and slowly bring the speed up, checking the venting until it runs to liquid. That little bit of beer you waste is well worth it to make sure you are exposing the entire filter stack to the run.
Hope you find out whats going on and get your desired flavor and aroma back!
Best,
SamComment
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As BrewMage22 mentions, it is very easy (too easy...) to have some air in filtration systems that can go on to cause oxidation problems. If at all possible, I would recommend a liquid purge rather than CO2; packing a system with deaerated water and venting to ensure all air is fully removed is the only sure way to eliminate the latter.Originally posted by aglfh3 View Post
The point about pumps is also a good one; also, any joints & connections should be checked to confirm they are in good, leak-free condition. It is quite possible for air to enter through a small leak, but not for beer to escape the same way (so the leak isn't evident externally).
As a lab-rat, I have spent many occasions chasing high DO2 levels, and invariably these have been the result of miniscule amounts of air, entering through poor joints, seals, etc. At ~20% oxygen, it takes very little air to cause an increase in DO2 levels.
To put some figures on this, a dissolved oxygen meter will read around 9ppm (=9000ppb) in air, a significant level. So, roughly, an oxygen level of 0.2% would give around 90ppb DO2.
Although, perhaps, I could be accused of bias as I am involved with dissolved gases instrumentation, I would strongly advise anyone to invest in an oxygen meter. This is the only sure way to know what oxygen levels you are working with - anything else is just guesswork.Comment
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As far as DO2 meters go, if we are looking at TPO, would we need to purchase a DO2 meter with a crown piercer or should we not be too worried about O2 pick up with the samples being exposed to air? We are a small brewery and would prefer to purchase just one device that can perform the entire range of tests that we need.Originally posted by TL Services View Post
Also, are there any other low cost means of deaerating water besides boiling or CO2 scrubbing? Thanks everyone for all your help!Comment
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You would need a piercer for analysing TPO from bottled samples.
A meter like the Orbisphere 3650 would allow you to cover-off all analyses throughout the process - from wort to final pack - so not only keeping control of costs, but also meaning all your measurements would be directly traceable back to the one meter, giving good analytical consistency.
Dearating water can be achieved quite simply/cheaply by recirculating a tank of water past a nitrogen injection point (pinpoint, stone, etc.). Have a DO2 meter running on a sample point and you can measure when you're down to low level.
Hope that helps!Comment
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