Questions about IBU calculation

[PapaDon]

I'm new to brewing and somewhat confused, my wife says I'm totally confused but that's a different subject. So here goes: I tried to figure the IBU of my current brew but get different results depending on the calculator used. "IBU Calculator " at Brewers Friend, HomeBrewing.com, a downloaded Excel spreadsheet and BrewersFriend's Recipe Designer software, are all different and not even statically close. So I'm confused. Which one if any is correct? Thanks

 

[Silver_Is_Money]

As to which is correct, the truth is that none of them are, because (aside from occasionally lucking out) none of the math models for IBU are going to get you anywhere close to lab measured IBU perfection. In reality roughly +/- 33% of lab tested IBU values is about all you can ever hope to consistently get out of the software models. In a podcast ominously titled "The IBU Is A Lie" one homebrewer who was part of the testing process was 70% off vs. lab testing for his IBU value on a submitted beer sample.

Some of the problem with the witnessed discontinuity in output across the various IBU calculators stems from their being multiple math models that all differ, and additional of it comes from different approaches to the implementation of the given math models.

Glen Tinseth, the man behind the math of what is likely one of the most used models stated on the same podcast that he never once tested a pellet hop, and that for pellet hops "All bets are off.".

I hope this doesn't further confuse you. Find a calculator you like and stick with it.

 

[Oginme]

To add to Silver Is Money's dead on response. Your best move is to get a few commercial beers with known IBU and brew something that calculates to a similar IBU. Choose one calculator and stick with that!!!! Now taste test your beer against the others and decide if you need to be higher in target number or lower or are you pretty close. THAT is your best path to attaining an IBU target for your recipes.

I think the actual IBU calculation involves the hop %AA, amount, gravity of the wort, time of the year, the astrological sign relating to the date the hop bine was originally planted, and a magic eight ball.

 

[PapaDon]

Cute, someone with a sense of humor I love it.

 

[BrewnWKopperKat]

Agreed, choose one calculator and stick with that.

"All models are wrong, some are useful" applies nicely to mathematically (aka software) estimated IBUs.

https://www.experimentalbrew.com/podcast/episode-32-ibu-lie. There is a follow-up article titled " The IBU is a LIE! Kind of....." https://www.experimentalbrew.com/experiments/writeups/ibu-lie-kind that makes the following observation: "we think the 'undershoot' is due to today’s more rapid chilling procedures than were common during the formula’s development."

Master Brewers podcast 123 (http://masterbrewerspodcast.com/) Tracking IBU Through the Brewing Process is worth a listen.

Basic Brewing Radio November 1, 2018 - IBUs vs Wort Gravity and Hop Stand Temps (http://www.basicbrewing.com/index.php?page=basic-brewing-radio-2018) and the associated PDF offer some interesting data as well.

And the "Hop Queries" newsletter (https://appellationbeer.com/blog/hop-queries/) will get you to articles on estimating IBUs at higher altitudes and lower temperatures.

 

[hottpeper13]

So Oginme, what you'er saying is the brew I made on the Super Snow Moon most likely had the correct IBU calculations!
I say screw the software and use Palmers math to do your own calculations. Get a beer of the same IBU's you think you have and side by side them, then adjust your utilization until you get what you are looking for. Perception is the only thing that counts. Whirlpools mater!!!

 

[Silver_Is_Money]

Dr. Chris White, the founder of White Labs, is apparently of the opinion that it is ones choice of yeast that will be the final arbiter which determines the hoppiness level of beer (vs. calculator predictions):

http://beerandwinejournal.com/yeast-strains-ibus/

I was amazed that White Labs research indicates that WLP029 yeast is among the few choices which typically result in only achieving about 50% of calculated IBU's. I'm all set to brew a Kolsch tomorrow using this yeast.

Overall, 2/3 of the 100 White Labs yeast strains tested resulted in IBU's that were less than the calculated IBU value.

 

[eric19312]

I'll pile on to the advice to get one calculator, stick with it, and use it to steer your recipe design decisions.

The key to being able to do this is to record your recipes and then record your tasting notes. With IPAs and other beers with dry hops involved it is good idea to taste the beers over time as the dry hops can provide some perceived bitterness while in suspension that may not correlate to IBUs calculated or measured in a lab. Then you need to rebrew the beer or at least something similar and use those tasting notes to make a decision for more or less bitterness.

I don't try calibrating my calculated IBU to commercially labeled IBU, it is difficult to know if the brewer is actually measuring the IBU in a lab or just providing the calculated value himself. I do know my local is just calculating. So comparing his IBU to my IBU is useless but when he says his pale has 50 IBU and his IPA has 90 IBU I know what to expect.

I like the Rager calculation and just stick with it.

 

[balrog]

As said, maybe better, find one and use it; specifically, if you feel a recipe needs higher bittering, next time use the same calculator but up the IBUs 20%. It's subjective, and you'll not notice 5 IBU difference either. Furthermore, remember that IBU are for bittering, and not hop flavor. There is no International Flavor Unit which will tell you that using 2oz Cascade at 5m from flameout give you more IFU than Centennial, or when added at 30m which drives off flavor/aroma.

 

[Soulshine2]

I'm new to brewing and somewhat confused, my wife says I'm totally confused but that's a different subject. So here goes: I tried to figure the IBU of my current brew but get different results depending on the calculator used. "IBU Calculator " at Brewers Friend, HomeBrewing.com, a downloaded Excel spreadsheet and BrewersFriend's Recipe Designer software, are all different and not even statically close. So I'm confused. Which one if any is correct? Thanks

I know the feeling. I use a brew calculator from a brew supply, and Ive seen more than a few times the values for the hops within the calc system are not what the hops actually are ...they're not too far off but not the same. Luckily there is a drop down to manually adjust whats actually listed on the package. Same with fermentable values on various malts.

 

[Silver_Is_Money]

I wonder if White Labs ever published the report which was alluded to in the dissertation at the link I provided in post # 7 above? It would help greatly if we all knew just where 100 or so of the White Labs yeasts stood in regard to their percentage of impact upon final beer IBU's.

 

[Oginme]

I don't try calibrating my calculated IBU to commercially labeled IBU, it is difficult to know if the brewer is actually measuring the IBU in a lab or just providing the calculated value himself. I do know my local is just calculating. So comparing his IBU to my IBU is useless but when he says his pale has 50 IBU and his IPA has 90 IBU I know what to expect.

Actually, I found it quite easy to call or write to the brewery to get an answer to this. Most of them were very forthcoming about if their values were calculated or tested. Of those which they said were calculated some stated that they developed their own calculation based upon testing of final product.

 

[dmtaylor]

The Tinseth equation is the best of the bunch... and it's not perfect either, as another pointed out that it was based on whole hop cones, not pellets. But for lack of anything better, it's the best, and is what I use and what I recommend.

For a ballpark number, you can use this approximation that I developed that follows pretty closely with Tinseth (try it and you'll see) AND which adds IBUs for hop stand / whirlpool / whatever you want to call post-boil hop additions:

IBU = oz * AA% * [sqrt(5*Boiltime)/V + sqrt(2*HStime)/V]

where
V is post-boil volume,
Boiltime is in minutes, and
HStime is post-boil hop stand time in minutes that it hangs around between about 150-190 F.

For multiple hop additions, put each one in separately, run the calc, then add up the total IBUs. It's not perfect, but it's pretty darn close for standard gravity worts of 1.050-1.060. At higher gravity (e.g., >1.080), change the sqrt 5 to 4 instead, and sqrt 2 to 1.5. At low gravity (e.g., 1.035-1.040), change the 5 to a 6, and the 2 to 2.5. Pretty close, and not too hard to memorize for those of us who like to formulate recipes on the fly on the back of napkins and such, that's the real reason why I took time to figure this out... that, and I'm a math nerd.

 

[Silver_Is_Money]

Remaining wort volume at the time of each hop addition is critical to a determination of wort density, which (combined with boil time remaining) is critical to determining potential hop utilization, and this may be where most of the math models differences in interpretation lead to differences in IBU prediction output, even if utilizing nominally the same math model. Some implementations use post boil volume across the board. Some implementations use pre-boil volume across the board. Many implementations split the difference and use a midway boil volume across the board. And some implementations actually try to calculate the most likely remaining volume present when each hop addition is made. Further to this end, some implementations attempt to correct volume to room temperature, and some more simply use volume at boil temperature.

For 'Mash Made Easy' I have made a number of adjustments and corrections (each leading to new version releases) since I added IBU calculation to it in an effort to compute (as it stands now, with version 6.25) the most likely room temperature adjusted remaining boil volume commensurate with the time of each hop additions introduction into the wort. I have no idea what other programs or programmers are doing in this regard, even hearkening back to the various math models origination and originators, but as to the calculated IBU output for each hop addition, the presumed volume (and thereby wort density) that one starts with for each hop addition makes a big difference at the end when all of the individual hop additions calculated IBU contributions are tallied up to achieve a final overall IBU "prediction".

But in the end it is merely a "prediction". And I believe that post #7 above has a lot to do with the accuracy of any mere prediction.

 

[Silver_Is_Money]

More on the subject of yeast having a huge impact upon IBU's. Some hard data:

http://tastingroom.yeastman.com/upl..._WLP940_WLP001_WLP830_WLP051_IBU One Page.pdf

 

[balrog]

 

[brewbama]

I recently ran into a discrepancy between calculators and determined there was a loose nut between the chair and the keyboard. Once I figured out not to check some box buried in a profile setting (how it got checked I have no idea), the calculations agreed between the calculators within my personal acceptable level of tolerance.

FWIW I use Tinseth. It gives me a reference number that I can correlate with my perceived bitterness produced on my system using my processes.

 

[Big Monk]

I recently ran into a discrepancy between calculators and determined there was a loose nut between the chair and the keyboard. Once I figured out not to check some box buried in a profile setting (how it got checked I have no idea), the calculations agreed between the calculators within my personal acceptable level of tolerance.

FWIW I use Tinseth. It gives me a reference number that I can correlate with my perceived bitterness produced on my system using my processes.

ProMash's "Kettle Size Factor" was aimed at manipulating Tinseth's 4.15 Time Divisor much the same.

Basically your Utilization Factor was:

U Factor = Kettle Size Factor * 4.15

 

[Silver_Is_Money]

You know things are getting weird when a totally hop free IPA tastes more bitter (as well as more characteristically proper) than an IPA with hops added.

In a double-blind taste test of two batches of the final hop-free pale ale compared to a regularly brewed pale ale, tasters found the hop-free beer to have more of the style’s characteristically bitter flavors.

https://qz.com/1233483/beer-made-by-genetically-engineered-yeast-can-taste-bitter-without-the-hops/

 

[balrog]

You know things are getting weird when a totally hop free IPA tastes more bitter (as well as more characteristically proper) than an IPA with hops added.
https://qz.com/1233483/beer-made-by-genetically-engineered-yeast-can-taste-bitter-without-the-hops/

Then what would they do for the antimicrobial hop action?

And the haze?

Oh right. There's always Tang.