Author Topic: IBU scales, why so different  (Read 3355 times)

Offline micsager

  • Senior Brewmaster
  • ******
  • Posts: 1003
    • View Profile
IBU scales, why so different
« on: September 13, 2012, 09:36:53 AM »
Beersmith allows you to calculate IBU's.  But it includes three different scales, and on my most recent IPA, one said 88, and another said 120.  I didn't check the third.  Why are these so different, and is one considered  "the gold standard?"


Offline denny

  • Administrator
  • I must live here
  • *****
  • Posts: 11665
  • Noti OR [1991.4, 287.6deg] AR
    • View Profile
    • Dennybrew
Re: IBU scales, why so different
« Reply #1 on: September 13, 2012, 09:51:54 AM »
I think Tinseth is the most universally used.  Years ago, I was told that Rager was most accurate for partial boils and Tinseth for full boils.  I use Tinseth and when I've had beers analyzed for IBU the results have been very close to what I get in Promash using Tinseth.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

Offline hopfenundmalz

  • Official Poobah of No Life.
  • *
  • Posts: 4536
  • Milford, MI
    • View Profile
Re: IBU scales, why so different
« Reply #2 on: September 13, 2012, 09:57:10 AM »
Tinseth also works well for me. I have converted kegs, so did Tinseth when he did his work. His is the calculator that was correlated to measurements.

There is the aricle Gordon wrote back in the Jan-Feb 2010 Zymurgy covering when he went to Sierra Nevada Beer Camp. Some guy's data for beers measured there are in the article.
Jeff Rankert
Ann Arbor Brewers Guild, AHA Member, BJCP Certified
Home-brewing, not just a hobby, it is a lifestyle!

Online kramerog

  • Brewmaster
  • *****
  • Posts: 784
    • View Profile
Re: IBU scales, why so different
« Reply #3 on: September 13, 2012, 10:27:38 AM »
The IBU calculators may provide IBU estimates of over 100 IBUs.  Such estimations are probably incorrect.  Some people say that people cannot taste IBUs in excess of 100.  Consequently I would go with 88 IBUs here. 
Brewers of South Suburbia
Brixie's Brewers
Oak Park Homebrewers

Offline denny

  • Administrator
  • I must live here
  • *****
  • Posts: 11665
  • Noti OR [1991.4, 287.6deg] AR
    • View Profile
    • Dennybrew
Re: IBU scales, why so different
« Reply #4 on: September 13, 2012, 10:39:06 AM »
The IBU calculators may provide IBU estimates of over 100 IBUs.  Such estimations are probably incorrect.  Some people say that people cannot taste IBUs in excess of 100.  Consequently I would go with 88 IBUs here.

But just because you can't taste it doesn't mean you can't measure it.  Admittedly, we generally taste our beers (!) but you can certainly have a calculated value above the taste threshold.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

Online kramerog

  • Brewmaster
  • *****
  • Posts: 784
    • View Profile
Re: IBU scales, why so different
« Reply #5 on: September 13, 2012, 10:42:55 AM »
The IBU calculators may provide IBU estimates of over 100 IBUs.  Such estimations are probably incorrect.  Some people say that people cannot taste IBUs in excess of 100.  Consequently I would go with 88 IBUs here.

But just because you can't taste it doesn't mean you can't measure it.  Admittedly, we generally taste our beers (!) but you can certainly have a calculated value above the taste threshold.

It's not clear to me whether IBUs over 100 is a tasting issue or a chemistry issue.
Brewers of South Suburbia
Brixie's Brewers
Oak Park Homebrewers

Offline denny

  • Administrator
  • I must live here
  • *****
  • Posts: 11665
  • Noti OR [1991.4, 287.6deg] AR
    • View Profile
    • Dennybrew
Re: IBU scales, why so different
« Reply #6 on: September 13, 2012, 11:11:40 AM »
The IBU calculators may provide IBU estimates of over 100 IBUs.  Such estimations are probably incorrect.  Some people say that people cannot taste IBUs in excess of 100.  Consequently I would go with 88 IBUs here.

But just because you can't taste it doesn't mean you can't measure it.  Admittedly, we generally taste our beers (!) but you can certainly have a calculated value above the taste threshold.

It's not clear to me whether IBUs over 100 is a tasting issue or a chemistry issue.

You mean as a solubility issue?  I'll try to remember to ask John Maier about it.  Rogue's Old Crusty comes in at 110 IBU supposedly.  it would be interesting to know how they arrived at that figure.  I'll also try to contact the lab that did the analysis or me and see what they have to say.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

Offline erockrph

  • Brewmaster General
  • *******
  • Posts: 2415
  • Chepachet, RI
    • View Profile
    • Critical Tastings
Re: IBU scales, why so different
« Reply #7 on: September 13, 2012, 11:25:28 AM »
You mean as a solubility issue?  I'll try to remember to ask John Maier about it.  Rogue's Old Crusty comes in at 110 IBU supposedly.  it would be interesting to know how they arrived at that figure.  I'll also try to contact the lab that did the analysis or me and see what they have to say.

I remember hearing a recent interview on one of the brewing podcasts with someone from White Labs (Neva Parker, IIRC) saying that their highest reading in the lab was a beer from Mikkeller that was ~150 IBU's. I'm wondering if it was their "1000 IBU" IIPA.
Eric B.

Finally got around to starting a homebrewing blog: The Hop Whisperer

Offline hopfenundmalz

  • Official Poobah of No Life.
  • *
  • Posts: 4536
  • Milford, MI
    • View Profile
Re: IBU scales, why so different
« Reply #8 on: September 13, 2012, 12:17:29 PM »
The highest lab measurement I have heard was 113 IBU. You do get into solubility limits above 110, and 110+ is hard to acheive.
Jeff Rankert
Ann Arbor Brewers Guild, AHA Member, BJCP Certified
Home-brewing, not just a hobby, it is a lifestyle!

Offline weithman5

  • Senior Brewmaster
  • ******
  • Posts: 1668
  • naperville, il
    • View Profile
Re: IBU scales, why so different
« Reply #9 on: September 13, 2012, 01:12:02 PM »
time to bitter with dandelion
Don AHA member

Offline Kaiser

  • Global Moderator
  • Senior Brewmaster
  • *****
  • Posts: 1797
  • Imperial Brewing Geek
    • View Profile
    • braukaiser.com
Re: IBU scales, why so different
« Reply #10 on: September 13, 2012, 04:14:54 PM »
Didn't Tinseh measure the IBUs of errors taken from the boil at different times? there is a loss on the order of 30% during fermentation.

I don't use IBU estimation.

But when I did, I quickly learned that it its only useful to compare your own beers. you should base your estimated IBU target on past beers you brewed that had the desired bitterness.

Kai

Offline hopfenundmalz

  • Official Poobah of No Life.
  • *
  • Posts: 4536
  • Milford, MI
    • View Profile
Re: IBU scales, why so different
« Reply #11 on: September 14, 2012, 05:12:49 AM »
Kai, that would be a good question for Tinseth.

I know that the numbers I got were for finished beer, and were pretty close to what the Tinseth formula said. Well except for the double IPA that was calculated to be very high in the 100 range, but tested at 67 IBU IIRC.
Jeff Rankert
Ann Arbor Brewers Guild, AHA Member, BJCP Certified
Home-brewing, not just a hobby, it is a lifestyle!

Offline nateo

  • Brewmaster General
  • *******
  • Posts: 2162
  • Aachen, DE
    • View Profile
Re: IBU scales, why so different
« Reply #12 on: September 14, 2012, 06:31:52 AM »
Here's a visual representation of a couple of different IBU formulae. I like Tinseth because his curve looks like a classical chemical reaction.



http://www.valhallabrewing.com/dboard/dbnewsl/t9509d.htm
In der Kürze liegt die Würze.

Offline Kaiser

  • Global Moderator
  • Senior Brewmaster
  • *****
  • Posts: 1797
  • Imperial Brewing Geek
    • View Profile
    • braukaiser.com
Re: IBU scales, why so different
« Reply #13 on: September 14, 2012, 07:01:41 AM »
Kai, that would be a good question for Tinseth.

It must have been an exchange I had with him a while back where he pointed me to the procedure he used. I just looked here: http://realbeer.com/hops/ and couldn't find it.

An inherent problem for estimating beer IBU from AA amount and boil time (and maybe hop product type) is that  beer IBU depends on many more factors. Some of the major factors that come to mind are:

- boil pH. It is known that higher boil pH extracts more bitterness
- bitterness lost during fermentation blow-off (I believe that this is a good thing)
- bitterness lost to yeast trub. I expect this to vary quite a bit
- non-linearity of bittrerness extraction. I.e one cannot extrapolate the bitterness extraction of a high AA concentration boil from low AA concentration experiments.

There is a reason why IBU calculators are largely a home brew thing. All the authors that came up with extraction formulas were home brewers. Without a doubt, there has been commercial research on that topic, but it has not yielded the extraction formulas that we are using. Commercial brewers do pilot brews and measure IBUs to correct the recipe or process.

If you know that a particular commercial IPA has 60 IBU, then this number came from actual IBU measurements and not from an IBU prediction based on the hop bill. If you like that bitterness and want to have it in your home-brew you may start aiming for 60 estimated IBUs, but you may have to correct the hops up or down after you tasted the beer.

I just think many, especially beginning brewers, trust these IBU calculators too much w/o knowing how they work and what their limits are.

Kai

Offline hopfenundmalz

  • Official Poobah of No Life.
  • *
  • Posts: 4536
  • Milford, MI
    • View Profile
Re: IBU scales, why so different
« Reply #14 on: September 14, 2012, 07:58:06 AM »
I agree with what you are saying.

In addition, some yeast will take more of the IBUs out than others. The pH drop during fermentation does cause more to precipitate out. It is a wonder you can make predictions at all.

A brewery of a fair size can run the measurements and tell what the utilization is for their system. Sierra Nevada publishes their IBU numbers and I think you can use those as a benchmark - within production variations.

Homebrewers often try to calculate the numbers and obsess over it because they can. If one also knows that your perception can only discern a difference of about 4 to 8 IBUs (depending on who you read), then there is not much point in stessing too much over it.
Jeff Rankert
Ann Arbor Brewers Guild, AHA Member, BJCP Certified
Home-brewing, not just a hobby, it is a lifestyle!