IBU seems off

[stijn26]

Hi,


Recently I brewed:

BIABacus Pre-Release 1.3T RECIPE REPORT
BIAB Recipe Designer, Calculator and Scaler.
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IPA - Batch 6​

Recipe Overview

Style: IPA
Source Recipe Link:
ABV: 3,4% (assumes any priming sugar used is diluted.)

Original Gravity (OG): 1,037
IBU's (Tinseth): 40,8
Bitterness to Gravity Ratio: 1,10
Colour: 7,2 EBC = 3,7 SRM

Kettle Efficiency (as in EIB and EAW): 89 %
Efficiency into Fermentor (EIF): 76,3 %

Note: This is a Pure BIAB (Full Volume Mash)

Times and Temperatures

Mash: 60 mins at 68 C = 154,4 F
Boil: 75 min
Ferment:

Volumes & Gravities
(Note that VAW below is the Volume at Flame-Out (VFO) less shrinkage.)
The, "Clear Brewing Terminology," thread at http://www.biabrewer.info/

Total Water Needed (TWN): 49,77 L = 13,15 G
Volume into Boil (VIB): 46,49 L = 12,28 G @ 1,031
Volume of Ambient Wort (VAW): 35 L = 9,25 G @ 1,039
Volume into Fermentor (VIF): 30 L = 7,93 G @ 1,039
Volume into Packaging (VIP): 27,78 L = 7,34 G @ 1,011 assuming apparent attenuation of 73 %

The Grain Bill (Also includes extracts, sugars and adjuncts)

Note: If extracts, sugars or adjuncts are not followed by an exclamation mark, go to www.biabrewer.info (needs link)

95% Muntons whole pale - maris otter (6 EBC = 3 SRM) 4918 grams = 10,84 pounds
5% CaraPils Weyermann (4,5 EBC = 2,3 SRM) 261 grams = 0,57 pounds


The Hop Bill (Based on Tinseth Formula)

9,2 IBU Chinook Pellets (11,2%AA) 9,8 grams = 0,346 ounces at 75 mins
15,3 IBU Chinook Pellets (11,2%AA) 34,4 grams = 1,213 ounces at 15 mins
4,6 IBU Mandarina Bavaria Pellets (7,8%AA) 14,7 grams = 0,52 ounces at 15 mins
4,4 IBU Chinook Pellets (11,2%AA) 24,6 grams = 0,866 ounces at 5 mins
7,3 IBU Mandarina Bavaria Pellets (7,8%AA) 58,9 grams = 2,079 ounces at 5 mins
0 IBU Chinook whirlpool Pellets (11,2%AA) 29,5 grams = 1,039 ounces at 0 mins
0 IBU Mandarina Bavaria whirlpool Pellets (7,8%AA) 88,4 grams = 3,118 ounces at 0 mins
0 IBU Manda + Chinook 50 50 Pellets (11,2%AA) 300,1 grams = 10,584 ounces at mins (Dry Hopped)

Mash Steps

Mash Type: Pure BIAB (Full-Volume Mash): Saccharifiaction for 60 mins at 68 C = 154,4 F

Strike Water Needed (SWN): 50,75 L = 13,41 G 68,5 C = 155,4 F



Now when I taste it, its quite unbalanced, It's a good beer but too bitter.
However it is only 40 IBU and the BU:GU ratio is not that out of whack I think.
What are the possible causes of this?

 

[Silver_Is_Money]

I suggest giving it several weeks to age and mellow (round) out a bit, and then tasting it again.

 

[Northern_Brewer]

Your calculator is ignoring any bittering contribution from 3oz of fairly-high alpha hops at 0 mins, and 14oz of dry hops. Which is something that a lot of them do - your actual bitterness is way over 40IBU, thanks to alpha contributions from any hops present whilst the temperature was >80C, and non-alpha bitterness.

I'd also not leave the dry hops in for too long - most of the flavour compounds come out within 24 hours, so 48 hours is plenty.

You might also want to replace some of that late Chinook with something with a bit less alpha.

 

[cactusgarrett]

As NB said, you may have only 40 formula-determined IBU in there, but all those other additions contribute more perceived bitterness. You run that through lab equipment, you very well could have 40 IBU, but perceived is a whole different beast.

 

[Silver_Is_Money]

Your calculator is ignoring any bittering contribution from 3oz of fairly-high alpha hops at 0 mins, and 14oz of dry hops. Which is something that a lot of them do - your actual bitterness is way over 40IBU, thanks to alpha contributions from any hops present whilst the temperature was >80C, and non-alpha bitterness.

Is there a bitterness calculator you recommend which takes flame out, hop stand/whirlpool, and dry hop additions into consideration with respect to their IBU contribution? The calculators I've seen, as well as my own, hit zero IBU at the zero minutes of remaining boil time mark.

 

[Northern_Brewer]

Some of them take a stab at calculating flameout hops at 10% utilisation, but it's unique to each person's process depending on time spent above 80C- to take one extreme, you might see utilisation of >50% in no-chill scenarios. 10% is a reasonable first guess though.

I think someone mentioned Scott Janish had got an analysis of a beer that was hopped entirely post-copper and it came back at 70 IBU, which gives you an idea of how big these effects can be.

A lot of these massive dry-hopped beers are increasingly seeing little hopping in the kettle, maybe a splash of bittering hops or alpha extract and a little bit late on, but as above, you are getting beers hopped entirely after flameout.

The bitterness calculators are struggling to catch up, particularly when it comes to perceived bitterness from non-alpha sources. For now, you have to rely on experience rather than a spreadsheet.