Difference In IBU Calculations?

[Jordan71017]

According to my calculations (I use the formulas in John Palmer's: How to Brew) the IBU's for a recipe I've been playing with are 135. When I use that recipe in BeerSmith the IBU's come out to 158. When I punch the recipe into ProMash it comes out to 248 IBU's. Does anybody know why this is or which one is more accurate?

 

[Bmorebrew]

There are different formulas for calculating BU - Tinseth, Rager, Garetz, for example. They each work differently, but in your case it won't matter. Typically you won't be able to get more than about 100 BU into the beer (as a rough estimate). The only real way to know is to measure by lab test.

 

[Jordan71017]

Thanks!

 

[TTB-J]

There are different formulas for calculating BU - Tinseth, Rager, Garetz, for example. They each work differently, but in your case it won't matter. Typically you won't be able to get more than about 100 BU into the beer (as a rough estimate). The only real way to know is to measure by lab test.

I agree in essence - it's not that you can't get more IBUs into a beer than 100, it's just that the vast majority of us really can't distinguish the difference in bitterness levels past that point. In other words, 100 IBUs is a rough taste threshold, after which it pretty much all tastes the same.

 

[rhamilton]

Once you get into the IBU range that high -- the formulas go out the window.

 

[JLem]

Estimated IBUs are just that- estimated. The various formulas set different parameters for how much bittering you get at different boil times and wort gravities. None are likely to be 100% accurate. Best thing to do is to pick one and stick with it. This way you can always compare apples to apples with your beers and you know what "35 IBUs" tastes like for your beers and can then adjust your hops appropriately as needed. I believe yhe Rager formula is used quite a lot by craft breweries and homebrewers, so that's what I use.

 

[BamaRooster]

Once I taste a beer with IBU's approaching 100, I can't taste anything else, except bitter, the rest of the night

 

[william_shakes_beer]

100m IBUs make my tongue squeak.

 

[Jordan71017]

Thanks to all for your input.

It just seems to me that when a beer's IBU's = the ABV times 10 (i.e. 10.2% ABV @ 102 IBU's or 5% ABV @ 50 IBU's, etc.) the beer tastes balanced to me. I'm designing a beer I hope will turn out to be 13% ABV so I was shooting for 130 IBU's, give or take a few.

 

[rhamilton]

It just seems to me that when a beer's IBU's = the ABV times 10 (i.e. 10.2% ABV @ 102 IBU's or 5% ABV @ 50 IBU's, etc.) the beer tastes balanced to me.

What is funny is you are exactly right!

Most people use a OG/IBU ratio of 1:1 to describe balanced beers - but ABV/IBU maps pretty much the same way, but in a 1:10 ratio.

 

[Yooper]

I agree in essence - it's not that you can't get more IBUs into a beer than 100, it's just that the vast majority of us really can't distinguish the difference in bitterness levels past that point. In other words, 100 IBUs is a rough taste threshold, after which it pretty much all tastes the same.

It's not just that- it is true that there is also a limit to the amount of hops oils that can be in a substance before it's saturated. The number I hear tends to be 100-120 IBUs and then it's just not possible for more.

I know my Pliny clone calculated out to something like 250 IBUs. But of course, that's a theoretical number, and if someone where to measure the IBUs in a lab it'd be more likely to be 90 IBUs or something like that.

 

[JLem]

It's not just that- it is true that there is also a limit to the amount of hops oils that can be in a substance before it's saturated. The number I hear tends to be 100-120 IBUs and then it's just not possible for more.

^ this

Just like salt or sugar, there is a limit to how much can be put into solution. And isomerized alpha acids really aren't that soluble to begin with.

 

[TTB-J]

I'm fairly certain, if I read Palmer's 2008 article on this correctly, that the limitation on iso-alpha absorption really doesn't necessarily have a limiting effect on IBUs. His article referred to a study on fresh vs. aged hops that actually had interesting results in terms of measuring IBUs:

That study illustrates two important points. First, that the standard international UV spectroscopy method for IBUs does not measure the actual concentration of iso-alpha acid, it measures the absorption at a specific wavelength of light of a group of compounds that are chemically similar to iso-alpha. Secondly, in the spectrophotometric method, compounds other than iso-alpha acids contribute to the measured IBU number — and this can yield similar IBU values in beers brewed with fresh or aged hops, despite differences in perceived bitterness. The other compounds that contribute to IBU in the spectrophotometric method include bitter oxidized beta acids, decomposition products of alpha and beta acids (which are not bitter) and some hop polyphenols (which are thought to be bitter), like xanthohumol.

Thus, IBUs doesn't really equal 1 mg iso-alpha acid per liter.

Edit: here's the link to the full article, please let me know if I'm just reading it wrong: http://www.byo.com/stories/article/indices/37-hops/200-behind-the-ibu-advanced-brewing

 

[Jordan71017]

Can you send your beer to a lab to get tested for IBU's? Not sure I'd really do it, just curious.

 

[BamaRooster]

Yep, white labs does it

http://www.whitelabs.com/beer/lab_services.html

 

[pjj2ba]

As far as which formula to use, I like to recommend that people pick one and stick with it. Then brew a bunch of beers with different hop levels to calibrate YOUR taste buds. Then when you build a recipe you will know from experience what 50 IBUs tastes like, for example and you can adjust your recipe.

In other words don't get hung up on the calculations. Just figure out what the different levels taste like and use that as your guide.

 

[frozt]

Not to get too far off topic, but does anyone know about how much white labs is charging for those lab services? I don't see any prices, but I'm sure it's not cheap.

 

[BamaRooster]

Not to get too far off topic, but does anyone know about how much white labs is charging for those lab services? I don't see any prices, but I'm sure it's not cheap.

They don't list any prices, somebody should call and ask!

 

[ArcaneXor]

It's $139 for two beers for Big QC day. Today is the last day to order for this year, but they will introduce more specific lab services for homebrewers later this year.

http://www.whitelabs.com/QC Day/BIG_QC_2012.pdf

 

[Jordan71017]

@ pjj2ba

I hear what you are saying but I like to try to clone commercial beers. I want my IBU's to be as close to theirs as possible on my first attempt. Do different breweries use different calculation methods or do they all get their beers lab tested?

@ ArcaneXor

I don't understand the website.......so do you send your beers in for testing or do they send you a kit so you can test your own?

 

[frozt]

I think they send you a kit with packaging materials, and you send the sample back.

 

[JLem]

@ pjj2ba

I hear what you are saying but I like to try to clone commercial beers. I want my IBU's to be as close to theirs as possible on my first attempt. Do different breweries use different calculation methods or do they all get their beers lab tested?

Some breweries estimate, some have it measured. Those that estimate may use any of the formulas. If you are trying to clone a commercial beer, you might contact the brewery and see if you can get some info about it. Most breweries I have contacted have been been very forthcoming with info.

 

[Jordan71017]

Thanks! You guys are great!