Home Brew Forums > Home Brewing Beer > General Techniques > Do you calculate alpha acid loss over time?
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Old 01-18-2013, 08:02 AM   #11
theveganbrewer
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Yes, there are lots of peer reviewed research and there are loss formulas.

Each variety has different rates of loss, but the producers have those numbers.

You can predict the loss fairly accurately and I think the results can matter if you are trying to produce a consistent beer over the course of a year between harvests.
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Old 01-18-2013, 01:36 PM   #12
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Quote:
Originally Posted by ocluke View Post
There have been a lot of articles published in peer reviewed journals on this. The excerpt below is from an old Brewing Techniques article from 2004 that does a decent job of scratching the surface, and references for further reading of published articles are cited at the bottom.
Hops start to lose their a-acids and oils as soon as they are harvested. The rate of loss depends on the storage temperature, the amount of air present, and the hop variety. The lower the temperature, the less the hops deteriorate. It has been shown that the rate of loss halves for every 15 degrees C (27 degrees F) drop in temperature (2).

That said, I rarely use IBUs for hoppy beers, because the majority of my hop additions are at or post flame out (all calculate at zero). For hop forward beers I pay more attention to the weight, oil content and "freshness" (as calculated by a highly scientific "whiff" test) of the hops that I'm using than the calculated bitterness units. Ironically, I do pay attention to IBUs when making beers that are yeast or malt driven, and in those cases it is more to make sure that I have some bitterness structure to hold up the beer. I normally do not use an alpha acid loss calculator, but it does make sense to do so.
Yes....yes it was ignorance. I apologize.
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Old 01-18-2013, 02:09 PM   #13
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Default calculating hop bitterness

I recently discovered the calculator on Beersmith and just started to use the calculator. I have 5 batches fermenting now, yea, that is a lot, but I wanted to do as much brewing before real winter set in and use up all my base grains before the new bulk bags came in. I will be able to give an update in about a month. Ive got an IPA, Stout, Wee Heavy, Smoked Porter and a Vienna Lager. There is a fairly decent amount of loss in the acid as the hops age as indicated by the calculator so its either going to be correct or way over hopped beer.
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Old 01-19-2013, 01:47 AM   #14
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Thanks, I will start using this calculator. Beersmith has a storage index for each hop if you click on the variety here: http://beersmith.com/hop-list/
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