Is there a limit to the IBUs you can get in wort?

[jkarp]

James Spencer had a podcast not too long ago with some scientist, where they experimented to try and determine maximum IBU content. The maximum they were able to measure, in a very simple beer, was ~60IBUs

Basic Brewing also did a collaborative experiment with BYO on partial vs full boil worts on March 4th, 2010. They had the actual finished beer IBUs lab tested and found very little difference in IBU utilization, even after diluting the partial boil wort by 50%.

Full pre-boil gravity: 1.068; OG 1.076; IBUs 66
Partial pre-boil gravity: 1.127; OG 1.070; IBUs 61

This pretty well blows a hole in the "100 max IBU theory" as this partial boil must have had well over 122 IBUs in solution after boil. Considerably more in fact, when you consider that yeast pull significant amounts of iso-alpha acids out of solution during fermentation.

This all begins to make sense when one listens to this excellent interview with John Palmer from back in 2008. I believe the homebrewer's 100 max IBU theory actually came from the work of Malowicki and Shellhammer who established that that the maximum solubility of alpha acids in beer is about 90 mg/L. After listening to Palmer's interview however, one will discover that 1 IBU is not equal to 1 mg/L of iso-alpha acid as many homebrewers still believe.

So what is the IBU limit of wort? It's clearly higher than 100, based on the empirical evidence alone. It would make an interesting experiment (master's thesis?) for someone with access to the appropriate lab equipment...

 

[mabrungard]

Basic Brewing also did a collaborative experiment with BYO on partial vs full boil worts on March 4th, 2010. They had the actual finished beer IBUs lab tested and found very little difference in IBU utilization, even after diluting the partial boil wort by 50%.

Full pre-boil gravity: 1.068; OG 1.076; IBUs 66
Partial pre-boil gravity: 1.127; OG 1.070; IBUs 61

This pretty well blows a hole in the "100 max IBU theory" as this partial boil must have had well over 122 IBUs in solution after boil. Considerably more in fact, when you consider that yeast pull significant amounts of iso-alpha acids out of solution during fermentation.

This all begins to make sense when one listens to this excellent interview with John Palmer from back in 2008. I believe the homebrewer's 100 max IBU theory actually came from the work of Malowicki and Shellhammer who established that that the maximum solubility of alpha acids in beer is about 90 mg/L. After listening to Palmer's interview however, one will discover that 1 IBU is not equal to 1 mg/L of iso-alpha acid as many homebrewers still believe.

So what is the IBU limit of wort? It's clearly higher than 100, based on the empirical evidence alone. It would make an interesting experiment (master's thesis?) for someone with access to the appropriate lab equipment...

Uhh...the references cited do not support your contention that an IBU is not equal to 1 ppm iso-alpha acid. Read here: http://www.byo.com/stories/article/indices/37-hops/200-behind-the-ibu-advanced-brewing

That article, which coincides with the interview cited, pretty much confirms that with typically fresh hops, the formulas and analytical results agree. The other component of the interview is that iso-alpha acids are NOT the only bittering components in beer. But, they are the MAJOR bittering components. Beta acids and other components influence the perception of bitterness.

Regarding the Basic Brewing results, I'm not sure how we got from those results to the contention that the partial boil wort had over 122 IBUs in solution after the boil. Clearly advanced math was used that I'm not familiar with. From my read of the Basic Brewing results, the maximum achievable IBU result still appears to be as I originally stated. IBU results in the 60's are significantly less than 75 IBUs.

 

[jkarp]

Uhh...the references cited do not support your contention that an IBU is not equal to 1 ppm iso-alpha acid. Read here: http://www.byo.com/stories/article/indices/37-hops/200-behind-the-ibu-advanced-brewing

From the very article you reference:

The definition of IBUs that most homebrewers are familiar with is one IBU equals 1 milligram (mg) of isomerized alpha acid per liter (L). (Equivalently, one IBU can also be expressed as one part per million (ppm) iso-alpha acids.) In practice, however, measured levels of IBUs in a beer may deviate from this definition.

Regarding the Basic Brewing results, I'm not sure how we got from those results to the contention that the partial boil wort had over 122 IBUs in solution after the boil. Clearly advanced math was used that I'm not familiar with. From my read of the Basic Brewing results, the maximum achievable IBU result still appears to be as I originally stated. IBU results in the 60's are significantly less than 75 IBUs.

So you're implying that plain water has IBUs, or that dilution has no effect on IBUs?

 

[the_bird]

The big thing that I wish someone could examine is IBUs in an unfermented wort versus IBUs in that finished beer. I suspect the latter is quite a bit lower. I mean - the original question, how many IBUs in a wort, is totally different from how many IBUs in a beer, since there's the whole fermentation aspect, time going by for alpha acids to settle, changes in pH, countless other effects. If you've got five gallons of isomerized hop extract, you should be able to make the wort's IBUs whatever you want, but that will not necessarily follow through to the beer.

 

[terrapinj]

how does water chemistry factor into the perception of bitterness vs actual IBU or isomerization?

do sulfates for example change the actual isomerization / IBUs (lab tested, not theoretical) or does it simply alter the perception of bitterness?

 

[jkarp]

100% agreed the_bird and terrapinj. Everything about IBUs is ripe for some solid empirical data. One could spend years working out various permutations.

 

[remilard]

The question is whether you can dissolve more than about 100 IBUs into solution, not whether you can taste them. If you only partial boil it will limit the maximum bitterness you can get in a beer to fairly low.

I've tasted things (mostly medicine) that have perceived bitterness orders of magnitude higher than any beer I've had. Anyone who things Pliny the Elder represents the maximum bitterness that can be perceived should go chew up a piece of aspirin as I believe that would convince them otherwise.

 

[hoppymonkey]

I've tasted things (mostly medicine) that have perceived bitterness orders of magnitude higher than any beer I've had. Anyone who things Pliny the Elder represents the maximum bitterness that can be perceived should go chew up a piece of aspirin as I believe that would convince them otherwise.

or anything with wormwood in it.

 

[LVBen]

I've tasted things (mostly medicine) that have perceived bitterness orders of magnitude higher than any beer I've had. Anyone who things Pliny the Elder represents the maximum bitterness that can be perceived should go chew up a piece of aspirin as I believe that would convince them otherwise.

Or just skim a little bit of the hops off of the surface of a boiling beer and put that in your mouth...