The Great IBU Test

drew's picture

Most of us geeky adherents to the world of homebrewing love our numbers. What's your efficiency rating, what's your gravity, your pH, your blah, blah, blah, blah..... There's a comfort, cold as it may be, in having a number we can look at. Numbers provide a reasonably solid, nonsubjective measure of the world - a target, a pin in the map. 

And so, no surprise, we measure everything in the beer world in an attempt to use numbers to measure something horrifically subjective and biologically wibbly. That includes bitterness with our much vaunted/touted IBU. "This beer has 50 kajillion IBUs and is so bitter it will scrape your tongue straight down to the lingual nerve!" But you know that thing is a fiction right? 

The quick and dirty IBU assay basically measures the absorbtion of light at a specific wavelength (275nm) and then multiply that by a fitting co-efficient (50). It's a rough fit estimation of perceived bitterness to the amount of dissolved iso-alpha acids. But there's a lot of stuff behind the perception of bitterness and the testing and the equations were mostly centered around the world of commercial brewing in the 1950-70's aka mid gravity lager brewing. 

Then we get into a second order of estimation in the brewing world when we try to predict what our IBU's. There are a number of prediction formulas out there that attempt to get from a baggie of hop pellets to the kettle to the IBU in the glass.  Boy do they vary too! One system's measurements might say "this is 77.7 IBUs" and another "93.4". The trick of course is to find one calculation, burn its meaning into your head/palate and use it. (The other part of the whole thing is these rough estimation calculations depending heavily on system geometry, boil velocities, etc. It's a mess and tough!)

For this experiment, we're going to have brewers from around the world brew up one of 3 recipes - a Basic Pale Ale, IPA and DIPA. We're going to compare the recipe calculations to actual measurement assays done on the various brewers beers. Plus we're going to put together a bunch of tasting notes to show the differences between the brews!

To help us ensure the "sameness" of our hops - our sponsor NikoBrew.com is going to provide the hops to our participating brewers so we can have even lots. (We'll also be testing the hops naturally to give our calculations the best shot).

We'd also like to thank the American Homebrewers Association for sponsoring this experiment! (Go download their new app - BrewGuru!)

Experiment Status: 

Subject: 

Proposed By: 

IGOR_Lead: 

Question: 

How do the IBU calculation formulas compare to the reality of IBU's in a beer when put to the test under different gravity scenarios

Hypothesis: 

They vary greatly from system to sysem.

Brewing Sessions Needed: 

1

Recipe: 

Special Observations: 

- As you brew, please record your kettle volumes over time, your initial kettle gravities

- Oh and photos of your boil kettle/burner setup as well! (This includes Pico style systems)

Experimental Procedure: 

  1. Choose one recipe out of the Basic Pale Ale / IPA / DIPA series. (If you're really ambitious do all three)
  2. Your hops will be delivered from NikoBrew (Drew has details)
  3. Brew, carefully recording all of your important variables. 
  4. Ferment, recording temperatures - skip the dry hop step for this experiment.
  5. Bottle and ship
    1. You'll be sending 3 bottles to Denny who will have one bottle assayed. One bottle tasted by him and one bottle tasted by me.
  6. Have a tasting! Record people's subjective experiences. Ask about bitterness levels. Serve beside commercial variants and ask participants to rank the beers in terms of bitterness.
    1. Pale Ale "Classic" : Sierra Nevada
    2. IPA "Classic": Stone IPA
    3. DIPA "Classic": Green Flash West Coast IPA
  7. The bottles shipped to Denny will be split between us and used for a hedonistic ranking test where samples will be ranked by multiple voters by bitterness levels and favorites. 

Experimenters Questions: 

  • Malt Choices - Which - Let's go domestic - for the munich - let's go Briess or Briess equivalent (L/Gravity)
  • Finings - None except optional Irish Moss
  • Dry Hop - No dry hop of the samples sent for analysis please
  • Mineral Profile - let's go your usual route (please note your water treatment)
  •  
CA_Mouse
CA_Mouse's picture
Can we get at least the base

Can we get at least the base recipe to start gathering the needed grains. I'm interested more because I plan on brewing all three. Typical of my experience, I'll do the DIPA first and then the other two either the next day or just brew three days in a row.

Bob

drew
drew's picture
All three recipes are linked
Andrew Brown
You're correct. They are

You're correct. They are listed above but I missed the hyerlinks at first too. Maybe it's my screen settings or something but the hyperlinks don't really show up that much different from the normal text.

Statsmats
Recipe error?

Drew...just entered the recipes into beersmith...the grainbill on the IPA is the same as the APA and comes in at 5.5%...think we need to scale up the IPA a bit to get the 7.5%.

Dave

drew
drew's picture
Good catch

Yup, transcribed that wrong - IPA has 13 lbs of 2-Row

Statsmats
Adjustment

Okay great. Based on my normal system efficiencies (low), I'm adjusting my water volumes from 5.5 to 5.25 gallons and seem to be hitting your numbers spot on...assuming this is the approach you want.

- Dave

drew
drew's picture
That's fine - primary targets

That's fine - primary targets are to keep IBUs on calculation point.

CA_Mouse
CA_Mouse's picture
Drew, I had to adjust my

Drew, I had to adjust my recipe in BeerSmith to match your IBU #s as well. Which IBU Scale are you using? I have enough hops to cover these changes.I noticed that the AAs on the packages I got are lower than your numbers in the recipe.

CTZ is 13.2% AA
Centennial is 9.4% AA
Cascade is 5.3% AA

Pale Ale dropped to .52oz
IPA increased to 1.21oz
DIPA increased to 1.88oz

Bob

drew
drew's picture
The initial calcs are Tinseth

The initial calcs are Tinseth I think. It's whatever BS2 defaults to. Are you adjusting because of your kettle dimensions, etc? 

CA_Mouse
CA_Mouse's picture
Lower AA percentages on hte

Lower AA percentages on the hops I received.

Bob

drew
drew's picture
Recipes were already adjusted

Recipes were already adjusted for the lower AA's from Analysis. Let's go with the indicated amounts.

CA_Mouse
CA_Mouse's picture
Now I'm confused. Which are

Now I'm confused. Which are the lower AA's? What is on the packages or in the recipes above?

Based on the AA's listed on the packages, the IBUs will be significantly off from the recipes above that contain higher AA's listed.

Bob

drew
drew's picture
Numbers from the hop analysis

Numbers from the hop analysis were as followed and should be reflected in the updated recipes, unless I goofed. (The number in the parens was what I originally calculated). Curious what it says on the package itself

CTZ - 12% (not 14%)

Cent - 7.8% (not 10%)

Cascade  - 4.4% (not 5.5%)

CA_Mouse
CA_Mouse's picture
CTZ is 13.2% AA

This is what is on my packages.

CTZ is 13.2% AA
Centennial is 9.4% AA
Cascade is 5.3% AA

The recipes above still have the 14%, 10% & 5.5%

Bob

drew
drew's picture
Ahh, forgot to change the

Ahh, forgot to change the recipe AA%'s as transcribed. All the amounts are correct for the analyzed values.

APA: 31.8 Garetz & Tinseth, 34.7 Rager

IPA: 57.8 G&T, 68.3 R

DIPA: 75.9 G&T, 93.9 R

CA_Mouse
CA_Mouse's picture
Thank you Sir! Just wanted to

Thank you Sir! Just wanted to make sure I was on the right page when I start mine on Sunday.

Bob

drew
drew's picture
Thank you for keeping me

Thank you for keeping me square and double checking my work!

CA_Mouse
CA_Mouse's picture
I think proofreading for MTF

I think proofreading for MTF and HBT has caused me to double check and re-read everything before passing them off as good to go!

Bob

BiochemBrewer
Mineral Profile

Is there any specific mineral profile you are looking for? or just whatever we would normally do for the style?

drew
drew's picture
In this case, I'd use

In this case, I'd use whatever you normally use. Make sure to note the water profiles you use because it will be interesting to see if we can suss out data.

CA_Mouse
CA_Mouse's picture
Sorry about that Drew, I didn

Sorry about that Drew, I didn't realize they were links since they were not colored.

Bob

drew
drew's picture
Yeah, they're very poorly

Yeah, they're very poorly colored. Gotta change that in the style shets

Siberian
Siberian's picture
Malts

Do you want particular maltsters?  Specifically on the "munich" because I think you could see some real variance in character there.  European Munich vs the Munich produced near me (Pilot) vs Briess is pretty varied. Though maybe not enough to impact a bitterness test...

drew
drew's picture
Let's stick domestic for this

Let's stick domestic for this run.

quirkzoo
quirkzoo's picture
Dryhop optional?

I noticed the recipes say "Dryhop Optional". It seems like in this instance we should control for that variable. I know that the classic forumulas typically don't factor dryhop into their IBU calculation but I also know that the general wisdom now is that it does in fact contribute "perceived" bitterness.

It might be cool for someone that has the ability to do a ten gallon batch to split it in half and dryhop one and have them tested side by side to see if there is a difference in perceived bitterness and IBU.

My T-Rex's name is Broccolisaurus

drew
drew's picture
Let me look through the

Let me look through the signups and we'll talk about it. For now, let's assume no dry hop since the dry hop IBU contribution is a bit iffy, but I do like the idea of getting one batch split with dry hops and no dry hops.

Thoroughbrews
Thoroughbrews's picture
This sounds like fun.

where do I sign up?

STB's

drew
drew's picture
This one is closed for now

This one is closed for now until we get final confirmation on hop #'s, but we have another awesome group brewing exercise coming up shortly.

CA_Mouse
CA_Mouse's picture
I can easily adjust any of

I can easily adjust any of mine to a double batch. 5.5 gallons is the absolute minimum that I can brew, so splitting one off after the boil would not be a major impact on me.

Also, are we using any finnings?

Bob

drew
drew's picture
Outside of Irish Moss, let's

Outside of Irish Moss, let's not.

CA_Mouse
CA_Mouse's picture
One more... Several versions

One more... Several versions of Munich Malt. Briess base Munich is about 10L and Weyerman is 5-7L. Not to mention that there are Munich Light, Medium and Dark...

So many choices.... I need a beer!

Bob

drew
drew's picture
Let's go Briess since that's

Let's go Briess since that's a solid readily available domestic choice.

Sean Dwyer
Any word as to when hops will

Any word as to when hops will be shipped?

sean

Sean

drew
drew's picture
We were just debating that...

Niko has sent off a set of hops for analysis which should be done in a few biz days. After that the hops should ship and be one the way!

BeardedBrews
DIPA Specific Questions

Pre-Boil Volume - 6.5 Gallons / 1 gallon per hour? (changes the boil gravity)

Table Sugar - Late boil addition or 60 minute addition? (changes the boil gravity)

Hop Steep - Preferred temperature for this steep? (changes isomerization rate)

FG - Is 9.2% ABV accurate (82% attenuation) for a 1.014 FG target?

drew
drew's picture
Sugar at start since the

Sugar at start since the calcs take into account the full gravity.

Yes, boil off rate of roughly 1 g/h

Steep let's go for everyone's favorite - just off the boil (I don't feel like any of our calculations have adjusted for reduced whirlpool temps) How do you feel about those answers?

BeardedBrews
I Feel

I feel warm and comforted, somehow more secure in my ability to exceed all expectations!

(Or, you know, just fine for a Tuesday)

I agree that the start of the boil is the most consistent, plus it gives the IBU calculators the best shot at being correct. Leaving the whirlpool as a wildcard might end up being where the variation in the experiment comes in. One other piece that might become important is the total time between flame-out and 70F. We know that a no-chill approach will increase perceived bitterness, so it would follow that variation in people's chilling approach could contribute to IBU in the lab. It might be good to have everyone record detailed times on that side.

Statsmats
Sugar

A follow on to Bearded...regarding sugar could this be added to the fermentor after full krausen? Been having success with my additional sugars in that way...or does that mess up the experiment?

Also...any type of sugar (beet/cane/brown/honey) or would that also muck up the waters for your tastings?

Ready to roll on three batches!

drew
drew's picture
Beet/Cane plain white sugar -

Beet/Cane plain white sugar - added to the boil. I think that wll be truest to calculations

CA_Mouse
CA_Mouse's picture
I'm liking this one....

I'm liking this one....

Free Hops (Thank You Niko!) - Check.
Free Specialty Grains (favor from one of my LHBS Thank You Vince!) - Check.
Free Yeast (White Labs Customer Club) - Check.
Free space to do tastings during a Brew Demo (Thank You More Beer - Riverside!) - Check.
Now if I can only figure out how to get free shipping to Denny!!!

Starters for the PA and IPA are on the stir plates, so I'm ready to start mine!

Bob

DryBoroughBrewing
TGIBD

2 kegs filled, spunding valves attached, and in the fermentation chamber.  Now, time for a beer.