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Brews & Views Bulletin Board Service * Brews and Views Archive 2005 * Archive through July 15, 2005 * Reference to max hop solubility < Previous Next >

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New Member
Username: Bigdog

Post Number: 20
Registered: 07-2003
Posted on Wednesday, July 13, 2005 - 12:52 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I have seen stated that 90 - 120 IBUs is the maximum limit for bitterness in a beer due to solubility and saturation of alpha-acids.

I have also seen other claims that 80-100 IBUs is the max human perception of bitterness.

Does anyone have any references or articles they can point me to documenting either of these?

Advanced Member
Username: Skotrat

Post Number: 815
Registered: 04-2003
Posted on Wednesday, July 13, 2005 - 02:09 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)


You may want to search through the HBD archives. The Great Al Korzonas did some studies about the human ability to perceive hop bitterness and such...

I want to say that it was in the 1999-2000 time frame.


New Member
Username: Bigdog

Post Number: 21
Registered: 07-2003
Posted on Wednesday, July 13, 2005 - 07:29 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks Skotrat!!! Nice memory,1998! HBD #2791 and #2797 Al Korzonas makes reference to 100 IBU being difficult to surpass. His source is The Practical Brewer, published by the MBAA.

Also a fellow club member found this for me:

In summary, Mitch Steelean, assistant brew master at Anheuser-Busch says:

"The maximum IBU level in a beer is somewhatd dependent on composition of the beer. A higher alcohol, higher gravity beer can have more IBUs than a beer at 5 percent alcohol. A 5 percent beer will max out at 120 parts per million iso-alpha acids, which corresponds to about 80 IBU. It is physically impossible to have more IBU than that in a 5 percent beer. As alcohol and unfermented carbohydrate in the beer increases, so does the ability of the beer to carry more IBU. Our hop
research expert feels that the claim that some barley wines have over 100 IBU is probably valid."

So it may be possible to exceed 100 with a big beer. The 120 parts per million iso-alpha acids is still consistent with ALK under a 5%ABv/w beer. Kind of ironic that this is from an AB guy!

Denny Conn
Senior Member
Username: Denny

Post Number: 4848
Registered: 01-2001
Posted on Wednesday, July 13, 2005 - 07:32 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Al Korzonas! One of the first books I got (and still one of the best) was Homebrewing Vol. 1. Sure wish he was as active in the HB world as he used to be.
LIfe begins at 60...1.060, that is.

Senior Member
Username: Hophead

Post Number: 1610
Registered: 03-2002
Posted on Wednesday, July 13, 2005 - 08:04 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Again, AB is a business, and they brew the beers that they can sell for the most profit. If IPAs were the peoples' choice, AB would be brewing IPAs, and they would be incredible...

Using the mighty recipator for my IPAs and IIPAs, I can't notice a difference once it gets over ~90 ibus as far as bitterness. Aroma is another story!

DJ Short
New Member
Username: Djshort

Post Number: 18
Registered: 02-2005
Posted on Wednesday, July 13, 2005 - 09:09 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

IBU is a representation of soluble alpha acids, but it is not always representative of the overall perceived bitterness of beer. Two beers with identical IBUs can have a totally different perceived bitterness due to several other factors ranging from the obvious to not so obvious:
Things like:
1) Other ingredients used in the beer that can contribute perceived bitterness (tannins, flavor compounds, yeast metabolism byproducts, etc..)
2) The drinker - different people have different sensitivities to bitterness and the ability to perceive bitterness evolves differently within different populations over time
3) Chemistry in the mouth - ion and pH of saliva have a significant impact of bitterness perception
4)History - What the consumer has tasted prior to drinking the beer - drink 2 consecutive, identical double IPAs and most people think the second one is less bitter than the first

IBUs are a number but don't always relate to how one will perceive bitterness and other flavors..

A good friend works at an analytical lab that does alpha acid solubility testing - hes never seen a value higher than 105 - that was in his own homebrew in which he boiled 16 ounces of hops for 3 hours with an OG of 25 plato. Interestingly, this beer finished with so much residual sweetness it didn't taste that bitter to me...

Some articles that may interest you can be found by searching online journal archives such as "Chemical Senses", "Physiology and Behavior", "Archives of Oral Biology" and some of the Food Science Sensory Science Journals....

Senior Member
Username: Fredrik

Post Number: 2393
Registered: 03-2003
Posted on Thursday, July 14, 2005 - 07:54 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I have seen a few references, some from MBAA and some other research articles. I tried to find the link now but I could't find it atm.

But, like has been said while the ballpark of IBU 100 may be some kind of rough max for a normal beer it is bound to depend on the composition, alcohol contents and certainly the pH. The alpha acids are acids, and the protolysis equiblirium is totally determined by pH.

isoAAH <-> isoAA(-) + H(+)

Higher pH favours isoAA(-) over isoAAH, which most certainly have much higher solubility.

It's well known that the impact of isoAA utilisation of pH during boil is huge. I think you can find much on the web by searching on humulone, pH and soubility.

This is why you can't say if the solubility is 100, 90 or 120. It can most certainly vary far more depending on some key facators like pH and ethanol contents.

I did some ballpark estimate and I wouldn't consider it impossible to hit maybe 200 IBU if the pH were to be 5.

I think this 100 IBU is a typical number for typical beer. If your beer pH is 4.2 or 4.5, I personally suspect the difference can be huge, I wouldn't think a factor two in IBU solubility to be out of the question.

I think one shouldn't hang up on wether it's 100 or 120. If you really want to know, then I would guess that you most certainly need to know etahnol contecnts and your beer pH accurate with two decimals.

FWIW, I did a silly and crude *ballpark estimate* before and it's not confirmed, but these estimates indicates that the impact of AA solubility of a pH shift of 0.1 could be as much as 25%. Probably not more though, but 25% is ALOT. It means 100 vs 125.