IBUs: standard calculation vs lab tested

[SocieteTravis]

I am looking for data to develop an equation for solving for the differential of calculated vs tested IBUs.

If anyone brews beers that are over 60 calculated IBUs AND later had them tested by a lab for their actual IBUs I would love information from you.
If you would be willing to share information, I would like for any given beer:

-The calculated IBUs (without any sort of hop saturation correction.) (If you could, include the formula you used for the calculation.)
-The laboratory tested IBUs
-The Original Gravity
-The Terminal Gravity

I will share any results with anyone who shares data with me.

[jwalts]

I took the lazy way out and modified my calculations based on a few data points:

-A Deschutes weblog (http://www.deschutesbrewery.com/blog...nd-statistics/) that describes a couple of beers brewed to a calculated 243 IBUs, which ended up at 80 and 87 IBUs after bottling.
-An article in either Brew Your Own or Zymurgy magazine (I don't remember which one) that compared various hop calculations to the lab results for beers that were brewed at a session of Sierra Nevada's Hop School. The very limited data suggested Tinseth's method (http://www.realbeer.com/hops/research.html) is most accurate and can be valid to about 65 IBUs. I wish I still had the magazine so I could back up these claims.

Basically, I multiply the Tinseth utilization formulas (adjusted for a brewhouse-based baseline utilization value) by the following multiplier when my target IBUs are above 65:

Multiplier = IBU/((IBU-65)*(240-65)/(85-65)+65)

So the Tinseth formula becomes [bigness factor x boil time factor x IBU concentration factor]. The multiplier is just an inverse linear equation, but at least it's bound by two lab-tested endpoints. It should be in a reasonable ballpark but, like you, I'd love to see more lab data. I also add a minimum limit for kettle utilization to account for alpha acid isomerization in the whirlpool.

Joe

[Chaz]

Yeah, as mentioned above, hops added to the whirlpool (where programs like ProMash will say it contributes nothing) will actually impart bitterness from sitting at the ~200dF temperature for that long period of time. I recently read 18% of Stone Ruination's IBUs actually come from the whirlpool addition.

Also worth noting, yeast pitching rate will have an effect.

[jfulton]

Whirlpool hops are not going to have a significant effect on IBUs, at least with standard whirlpooling practices. The relatively cooler wort, the already high level of isomerized acid, and the fact that the hops settle into the cone, not being turned over in convection, will greatly reduce utilization. I find it hard to believe that any brewery is getting near 20% of their bitterness from a whirlpool addition. However, I have heard of some brewers that whirlpool for like 45 minutes, before even beginning the rest ! That's another issue altogether though...

[Chaz]

I find it hard to believe that any brewery is getting near 20% of their bitterness from a whirlpool addition. However, I have heard of some brewers that whirlpool for like 45 minutes, before even beginning the rest ! That's another issue altogether though...

Well, it came directly from Mitch himself... He said about 18% IBUs and they get about 9.6% utilization on whirlpool hop addition for that beer where the whirlpool is a 15 minute fill, 15 minute rest and and 45 min knock out. So 75 minutes of 18dP wort at ~200dF according to what he wrote.

Pelican Pub's Kiwanda Cream Ale's only addition of hops is at the whirlpool and they publish that they end up with 25 IBUs in that. I'm not sure if that's estimated or calculated though.

But you are right, I'd imagine batch size, wort gravity, process and equipment would be a big variable in how much bitterness is actually extracted from a whirlpool addition.

[jwalts]

Matt Brynildson, a former hop chemist, claims to get 22% whirlpool utilization at Firestone Walker (50-bbl system) and to have gotten 15% whirlpool utilization on a 10-bbl brewpub system. Keep in mind that even if you employ a standard 10-minute whirlpool followed by a 20-minute rest, a lot of your wort is still in hot contact with the hops while it waits to go through the chiller. This doesn't just affect the utilization of whirlpool additions, but late boil additions as well.

Another interesting point, illustrated by the Rock Bottom hop experiment presented at the 2009 Craft Brewers Conference, is that perceived bitterness correlates with perceived hop flavor and aroma more closely than it does with IBUs measured in a lab. We can argue about IBU utilization until we're blue in the face, but it won't change the fact that you can make a hoppy-as-hell beer by adding most of your kettle hops in the whirlpool.

Joe

[J.M.Martin]

I do believe you will have to formulate an in house equation from your own data. There is just too much variation from brewhouse to brewhouse; from the individual brewer’s process to the equipment. I believe we all know the equations we use to calculate IBU’s are not exact but with in house data and out of house lab results you can formulate an equation specific to your Brewhouse. White Labs has their Big QC Day coming up that might be a nice inexpensive way to get a handle on your actual IBU’s.

Cheers

jamie

[pbutlert]

Well, it came directly from Mitch himself... He said about 18% IBUs and they get about 9.6% utilization on whirlpool hop addition for that beer where the whirlpool is a 15 minute fill, 15 minute rest and and 45 min knock out. So 75 minutes of 18dP wort at ~200dF according to what he wrote.

Pelican Pub's Kiwanda Cream Ale's only addition of hops is at the whirlpool and they publish that they end up with 25 IBUs in that. I'm not sure if that's estimated or calculated though.

But you are right, I'd imagine batch size, wort gravity, process and equipment would be a big variable in how much bitterness is actually extracted from a whirlpool addition.

Our procedure for Kiwanda is to add all the hops at boil stop, ramp down the kettle temp., whirlpool for about 3 mins., and then rest for about 30. Knock-outs take about 30 mins. We send all our beers to Analysis Labs here in Oregon, where IBU's are measured as low as 21, and as high as 29 consistently. Darron had a mention in Brew-Your-Own magazine a few months back, and Matt from Firestone also talked about adding hops at whirlpool in this article.

[Chaz]

This doesn't just affect the utilization of whirlpool additions, but late boil additions as well.

That's a good point too.

Our procedure for Kiwanda is to add all the hops at boil stop, ramp down the kettle temp., whirlpool for about 3 mins., and then rest for about 30. Knock-outs take about 30 mins. We send all our beers to Analysis Labs here in Oregon, where IBU's are measured as low as 21, and as high as 29 consistently. Darron had a mention in Brew-Your-Own magazine a few months back, and Matt from Firestone also talked about adding hops at whirlpool in this article.

Thanks for the clarification. Would you be able to give a ballpark on how many pounds per barrel you add at boil stop?

[pbutlert]

11 pounds. We usually knock out 18-19 barrels.

[gdebisschop]

It only makes sense that whirlpool additions add bu's- if you're above isomerization temp, alot of that wort will be there for a considerable amount of time. When I was at Siebel we had "old school" beer guys teaching full utilization for all additions, and all the craft guys (myself included) shrugged it off as old school thinking. Years later we did some analysis and found that at the brewery I was working in (which did have relatively long knockout times) all additions were more or less at the same % utilization- at least from lab feedback and our calculations that's what we backed into.

cheers
geoff

[eoconnor101]

I have only had 2 batches tested but have approximated that we get about 25-30% utilization at whirlpool and from late boil additons. But 60 minute hop additions are completely utilized by knockout so FWH additions are treated the same as 100% utilized. Using BS2 I can roughly estimate IBUs in beers below 60-65 IBUs, however I do believe it starts to be inaccurate in bigger beers and those with more calculated IBUs. I will admit further testing is needed. I plan to test several recent batches of beers calculated over 65 IBUs and will be happy to post the data here.