Calculating AA in Homegrown hops

Physics, chemistry and biology of brewing. The causes and the effects.

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Calculating AA in Homegrown hops

Postby skotti » Tue Feb 12, 2008 6:58 pm

I am starting to grow my own hops and I am wanting to know the AA for them. Does anyone know what is the easiest way to test them? My BS is in chemistry and the only way I can find is NIR after titration. And without buying a microgram scale and NIR the ASBC method below is inaccurate.

http://www.realbeer.com/hops/ASBC.html

Does anyone know if there is a lab that does this test?

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Bitterness

Postby slothrob » Tue Feb 12, 2008 9:18 pm

I think you'd be better off making a small batch and using the spectrophotometric method. Then you only need a micropipetor and access to a centrifuge and a spectrophotometer.

...or, you could do what I do. Assume the alpha content is average for the hop strain. Make a small batch of a beer recipe that you know well and is forgiving in the bitterness level (an APA isn't a bad idea). Taste the beer and see if it's in the balllpark.

If it's any consolation, 10 people making the same beer with the same hops will make beer that varies in IBU by 20 to 50%. Most hop varieties only vary in %aa by about 10-20% from average, so using the average as a best guess probably won't put you too far off.

Also, remember that we can only distinguish a difference of 5-10 IBU between 2 beers. If you design your beers with this in mind, you can have a pretty good idea that the typical variation of that hop strain won't have a discernable effect on your beer.

Other than that, I think I remember reading that Hopunion does IBU or %aa testing for a fee. You can try contacting them.
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Home tests for AA% of homegrown hops

Postby billvelek » Wed Feb 13, 2008 12:28 pm

Gentlemen, I am not a chemist and I have a fairly weak background in chemistry -- having only taken Chem 101 in college nearly 30 years ago. However, in response to this thread, and particularly the original post, let me mention that there has been some recent discussion of using titration as a home test for AA over on my Grow-Hops Group -- http://groups.yahoo.com/group/Grow-Hops -- which now has 961 members. It seems, afterall, that titration might not actually be an accurate test of AA in particular, because if it just checks pH, then the beta-acid isn't being ignored, is it? I don't know if there is a 'work around' for that. Anyway, if you happen to grow hops -- or even if you don't but think you might have a solution that could help us -- I encourage you to join us and add your comments to this thread: http://groups.yahoo.com/group/Grow-Hops/message/1749. Thanks for any help.

Cheers.

Bill Velek
Visit www.tinyurl.com/bvelek - portal to my brewing sites: 3,100+ members on 'Grow-Hops', and 1,350+ brewers on my 'BrewingEquip' group.
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