wait why am i getting two different IBUs for same recipe?

[TacoGuthrie]

I've plugged my recipe into beersmith and then into the online hopville recipe creator. I'm getting way different IBUS. 70 vs 40?!? Can anyone help explain why this is. Which one is correct?

Also I should note i only have a 16qt brewpot so do partial boils but shouldn't that basically increase my ibus?

Beersmith:
--------------------------
Batch Size: 5.00 gal
Boil Size: 5.72 gal
Estimated OG: 1.066 SG
Estimated Color: 5.8 SRM
Estimated IBU: 72.9 IBU
Brewhouse Efficiency: 70.00 %
Boil Time: 60 Minutes

Ingredients:
------------
Amount Item Type % or IBU
5.00 lb Pilsner Liquid Extract [Boil for 15 min] Extract 45.45 %
3.00 lb Pale Malt (2 Row) US (2.0 SRM) Grain 27.27 %
2.00 lb Vienna Malt (3.5 SRM) Grain 18.18 %
0.50 lb Cara-Pils/Dextrine (2.0 SRM) Grain 4.55 %
0.50 lb Caramel/Crystal Malt - 10L (10.0 SRM) Grain 4.55 %
1.00 oz Simcoe [12.20 %] (60 min) Hops 39.2 IBU
0.50 oz Simcoe [12.20 %] (15 min) Hops 9.7 IBU
1.00 oz Simcoe [12.20 %] (5 min) Hops 7.8 IBU
1.00 oz Simcoe [13.00 %] (1 min) Hops 1.8 IBU
1.00 tsp Irish Moss (Boil 10.0 min) Misc
10.00 gm Gypsum (Calcium Sulfate) (Mash 60.0 min) Misc
1 Pkgs Nottingham (Danstar #-) [Starter 25 ml] Yeast-Ale

% LB OZ MALT OR FERMENTABLE PPG °L

43% 5 0 Pale Liquid Extract 36 4

26% 3 0 American Two-row Pale 37 1

17% 2 0 Vienna Malt 36 3

4% 0 8 Cara-Pils/Dextrine 33 2

4% 0 8 Caramel/Crystal Malt - 10L 35 10

4% 0 8 Corn Sugar (Dextrose) 46 0

Batch size: 5.0 gallons edit
Original Gravity
1.073
(1.065 to 1.076)
Final Gravity
1.017
(1.015 to 1.019)
Color
5° SRM
(Yellow to Gold)
Mash Efficiency ?
70% edit
hops
USE TIME OZ VARIETY FORM AA

Boil 60 mins 1.0 Simcoe leaf 12.2

Boil 15 mins 0.5 Simcoe leaf 12.2

Boil 5 mins 1.0 Simcoe leaf 12.2

Boil 1 min 1.0 Simcoe leaf 12.2

Boil: 3.0 avg gallons for 60 minutes edit
Bitterness
12.2 HBU
40.5 IBU
ƒ: Average edit
BU:GU
0.56
yeast

Nottingham Ale Dry Yeast
ale yeast in dry form with medium to high flocculation
Alcohol
7.5% A.B.V.
5.8% A.B.W.
Calories
240 per 12 oz

 

[carbon111]

IBUs will vary depending on what formula you use. Tinseth, Garetz and Rager all come up with different numbers - the Hopville calculator is an average of those three plus their own. Rager seems more out-of-whack than the others, giving much higher numbers.

AFAIK, your software can be set to use whichever formula you like best.

Smaller boils give less hop utilization as higher gravity worts extract less bitterng agents - in your examples above, one boil is set at 3 gallons and the other at 5.72.

One nice thing about full boils is the ability to use fewer hops to get the same IBUs.

 

[TacoGuthrie]

hmmm

i just checked tools>options in my beersmith (can you tell i'm a new user??) and it says I'm using Tinseth.

I just wanted to make an IPA with a BU:GU of at least 1.

I guess i'll play around with it.

 

[carbon111]

Also, remember to set your actual boil size in your software and on Hopville to get more consistent, accurate results.

 

[TacoGuthrie]

I had Beersmith set up to match my equipment. Then Vista crashed on me at the end of last week. I spent most of saturday reinstalling the OS and a lot of the software I lost.

So I had to reinstall Beersmith. btw Brad at the Beersmith forums (the mod) was really helpful in getting me back up and running and finding my old recipes files buried in windows directories. The point is that I didn't setup my equipment again in teh re-installed software including your point about boil volume.

I brewed that IPA tonight and it was hellish. Stuck sparge on my mini mash tun, near boil overs because i wasn't getting that much boil off. On and on.

Tough day but thanks for the points carbon!

 

[carbon111]

Sorry to hear the day was such a pain. RDWHAHB.

Here's hoping your IPA turns out "just right".

 

[TacoGuthrie]

May have been a pain at the time but I loved it. Always learning new things.

 

[gxm]

Using a full 5 gallon boil, putting the values into my spreadsheet (using Tinseth), I get the same IBUs as Beersmith for the 4 hop additions, 39, 10, 8, 1.8, which add up to 58, not 73.
If I change to using a 3 gallon boil (~100 BG), and use water to hit 5 gallons, I get 39.
So, these two programs are calculating the same thing, you've just given them different input parameters.
The high BG using all the extract upfront is why many extract brewers add half the extract at the start of the boil, and the other half extract at sometime between 15 mins and knockout. This lowers the BG to a value close to the final value, and helps approximate the hop utilization you'll get with a full boil.
If you do that, and bump up your initial 60 min hops to 1.2 oz, you'll get pretty close to 1 BU:GU. You can also increase the IBUs by adding hops earlier, such as hopping the same amounts at 60, 20, 10 & 1.

Good luck

 

[SumnerH]

Using a full 5 gallon boil, putting the values into my spreadsheet (using Tinseth), I get the same IBUs as Beersmith for the 4 hop additions, 39, 10, 8, 1.8, which add up to 58, not 73.
If I change to using a 3 gallon boil (~100 BG), and use water to hit 5 gallons, I get 39.

So, these two programs are calculating the same thing, you've just given them different input parameters.
The high BG using all the extract upfront is why many extract brewers add half the extract at the start of the boil, and the other half extract at sometime between 15 mins and knockout. This lowers the BG to a value close to the final value, and helps approximate the hop utilization you'll get with a full boil.

Be careful with the partial boil settings, they're based on the (now known to be incorrect) assumption that hop utilization varies with the gravity of the wort. Smaller boils will give you slightly lower utilization because of physical phenomena, but not nearly as dramatically as most brewing software calculates--you're better off listing every boil as a full (or nearly full) boil than going with the utilization methods that current brew software uses.

The March 20 podcast here ("What is an IBU, really?") has some good info from John Palmer on the subject. Basic Brewing: Home Brewing Beer Podcast and DVD - Basic Brewing Radio: 2008

One conclusion he reaches is that late extract addition is still a good idea (especially to stop maillard reactions and keep color light), but it's not really got anywhere near the affect on hops utilization that the home brewing community thought it did even 2-3 years ago.

It's not at all new news in the commercial brewing world, though; you find plenty of papers going back to the 1980s pointing out that boil gravity doesn't affect utilization. E.g. the American Society of Brewing Chemists ASBC Journal 1989 - Hop Utilization in the Brewery-An Interbrewery Comparison. in 1989 saying "In the range 10.5-13.5° P, no relationship between hop utilization and original gravity was found" (a range that's been extended by further study since then).

 

[SumnerH]

I've plugged my recipe into beersmith and then into the online hopville recipe creator. I'm getting way different IBUS. 70 vs 40?!? Can anyone help explain why this is. Which one is correct?

They're probably both wrong. IBU formulas are kind of a crapshoot attempt at estimating what the real IBUs are going to be, and none of them are 100% accurate. In practice, the important thing is to pick one and stick with it, so that you have a consistent baseline to work from

I wrote up a comparison of tests from one BBR episode, where they made a recipe and calculated the IBUs using 5 different algorithms, then had the actual IBUs measured for the beers:
https://www.homebrewtalk.com/f128/estimating-bitterness-algorithms-state-art-109681/#post1209569

For one beer, the Garetz algorithm calculated that it would be 10 IBUs. Daniels had it at 64 IBUs. Tinseth had it at 38. That's a really wide range of estimates, obviously. It measured out to 34. Which algorithm was closest varied based on what kind of beer was being made, but if you look at all the results you can see some are more often way out of line. I go with Tinseth, just to have a standard base to work from.

Even at a relatively simple level, most formulas have a lot of room to improve their estimates--e.g. none of them take the kind of fermentables you're using into account but some do dramatically alter results for partial boils. In reality using, wheat malt is going to have a much larger effect on actual IBUs than doing a 3.5 gallon boil will.