Help me understand the IBU Calculation

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gcdowd

gcdowd

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For fun, I was playing around with the timing of my DME additions to see how it would affect the IBUs of an IPA I've been working on. Noticed that if I put half the DME in at the beginning and half at the end, it changes my IBU calculation by about 30 IBUs. I understand that with a lower boil gravity, the hop can better utilize because it doesn't have to "compete" with the malt (I think that's right). Anyway, 30 IBUs seems like a heck of a difference. Knowing that my boil is only 3 gallons and the total volume will be 5, is that accounted for in the final IBU calculation? I'm using an app on my phone for the calculations (called BrewR). Anyway, below is the recipe and I'm hoping someone can verify my IBUs. I'm kind of a hop head but am not sure if this will be too bitter (currently the recipe is giving me an IBU of 97 and I believe it uses Tinseth).

8# of light DME (4# at beginning of boil, 4# at 15 min)
1# Crystal 20L (steeped for 30 min before boil)

Hop schedule:
1 oz Centennial (8.9%) @ 60 min
1 oz Centennial (8.9%) @ 45 min
1 oz Amarillo (9.3%) @ 30 min
1 oz Cascade (6.4%) @ 15 min

Dry Hop
1 oz Cascade
1 oz Amarillo
 
IBU calculations are a WAG. You don't know your kettle's utilization, you don't really know your AA% (They pull samples for testing from giant bundles of hops, so there's really no way to know your AA% exactly). You don't really know how long ago your hops were picked or how they were stored. There are also elements in your water chemistry that can lead to perceived bitterness that the calculators can't predict.

It would basically be impossible for you hit 97IBU, as verified by a lab, with this recipe. That's good since there's not nearly enough malt to carry that many IBU.

The only thing useful about IBU calculators is that you can use them as a relative measuring tool. Let's say your formula thought it would be "70." If "70" is too bitter, next time try "60." But there's little relation between "70" and a lab-tested 70IBU.
 
gcdowd said:
Ok thanks. In your opinion, is my hop schedule decent for an IPA?
Click to expand...

No. You should get rid of the 45 minutes addition, and possibly move the 30 minute to about 20. Then take your two ounces from 45 minutes and 15 minutes and spread them out among the last 15 minutes. Leave some for flameout.

This is just my opinion though...
 
+1 to Nateo comment....its all a guess, and one that you can make yourself crazy over. My suggestion is to use a calculation that is easier for you to make (by this I mean: use whatever one is used by your brewing software, one that is used by a website you like, one that you have in a excel spreadsheet, etc). and go with it.

Take that number and see if it gets you in the ballpark for the style you are brewing (i.e. does 65 IBUs give you a IPA of suitable bitterness?). Chances are it will. If it doesn't, adjust the % utilization figure in the IBU calculation accordingly.

Hope this helps.
 
Suthrncomfrt1884 said:
No. You should get rid of the 45 minutes addition, and possibly move the 30 minute to about 20. Then take your two ounces from 45 minutes and 15 minutes and spread them out among the last 15 minutes. Leave some for flameout.

This is just my opinion though...
Click to expand...

I agree. If you need more bittering, move some hops to 60 minutes. But move the 45 minute and 30 minute hops.

IPAs are about a firm bitterness with lots of hops flavor. Hops added to the kettle before the last 20 minutes of the boil impart bitterness, but not much flavor. Hops added at 15-20 minutes left in the boil are the hops that provide the flavor. Hops added after 15 minutes left in the boil are for flavor as well, but provide much more aroma. That's because the longer hops boil, the more the oils in them are isomerized. IPAs have much more hops flavor.

A good schedule for an IPA would be more like this:

Hop schedule:
1.5 oz Centennial (8.9%) @ 60 min (or enough hops to give enough bitterness)
1 oz Cascade (6.4%) @ 15 min
.5 oz Centennial (8.9%) @ 5 min
1 oz Amarillo (9.3%) @ flame out

Dry Hop
1 oz Cascade
1 oz Amarillo
 
Also are you sure you want to be using such high AA hops for the finishing hops? Most of the time those are the noble varieties with a very nice aroma and taste with low bittering. I agree completely with the above comments.

Also IBU has to do with hop utilization. The places growing them can get a very good estimate of their AA levels, but adding hops at flame out will give very different properties than 60min however add the same amount of IBUs. What you really care about is hope utilization and boil off. The longer a hop boils the less flavour and aroma are imparted to the beer and the more alpha acids are converted into iso-alpha acids which are very stable and cause the bitterness. Look up hop utilization, there are many tables which list percentages at various times. Bitter at 60min and add the rest between 20 and 0min, or add them all as late hop additions.

I am just surprised to see the varieties chosen, are they really good flavor and aroma hops? I don't generally deviate too much in any of my beers above the 5% except in rare circumstances with using a goldings variety. Tell use how it turns out, I am curious.
 
Thanks everyone, I think I will use the hop schedule that Yooper suggested. This is my first attempt at a hop schedule so your input is invaluable. Thanks again!
 
asterix404 said:
Also are you sure you want to be using such high AA hops for the finishing hops? Most of the time those are the noble varieties with a very nice aroma and taste with low bittering. I agree completely with the above comments.
Click to expand...

In an American IPA? Centennial and Amarillo are *awesome* for aroma and dry hopping. Plus the AA% of late additions doesn't really matter all that much unless you whirlpool/hot steep for a while. If you knock the temperature down to below ~180 degrees within 5 minutes, the difference in additional bittering imparted by a 4% AA and a 10% AA flameout hop is very small.
 
asterix404 said:
Also are you sure you want to be using such high AA hops for the finishing hops? Most of the time those are the noble varieties with a very nice aroma and taste with low bittering. I agree completely with the above comments.

Also IBU has to do with hop utilization. The places growing them can get a very good estimate of their AA levels, but adding hops at flame out will give very different properties than 60min however add the same amount of IBUs. What you really care about is hope utilization and boil off. The longer a hop boils the less flavour and aroma are imparted to the beer and the more alpha acids are converted into iso-alpha acids which are very stable and cause the bitterness. Look up hop utilization, there are many tables which list percentages at various times. Bitter at 60min and add the rest between 20 and 0min, or add them all as late hop additions.

I am just surprised to see the varieties chosen, are they really good flavor and aroma hops? I don't generally deviate too much in any of my beers above the 5% except in rare circumstances with using a goldings variety. Tell use how it turns out, I am curious.
Click to expand...

Umm, centennial, cascade and Amarillo are Devine flavor/aroma hops, IMO and that of many others. Quite popular too.
And maybe I read this wrong, but you said a 60 min add and a flameout add give the same ibu's just different 'properties'? Not to be that guy (ok, to be that guy), I think you're way off. A flameout add lends almost no IBU, where an add boiled for 60 mins could have up to 30% utilization, lending a good amount of IBU. Look up 'hop utilization', plug some #'s into brewing software, experiment in your beers.

To the op, +1 on yooper's schedule.
 
asterix404 said:
Also IBU has to do with hop utilization. The places growing them can get a very good estimate of their AA levels, but adding hops at flame out will give very different properties than 60min however add the same amount of IBUs. What you really care about is hope utilization and boil off. The longer a hop boils the less flavour and aroma are imparted to the beer and the more alpha acids are converted into iso-alpha acids which are very stable and cause the bitterness. Look up hop utilization, there are many tables which list percentages at various times. Bitter at 60min and add the rest between 20 and 0min, or add them all as late hop additions.

I am just surprised to see the varieties chosen, are they really good flavor and aroma hops? I don't generally deviate too much in any of my beers above the 5% except in rare circumstances with using a goldings variety. Tell use how it turns out, I am curious.
Click to expand...

I bolded the incorrect line in the above. The 60 minute addition will provide far more IBUs than a 30, 15, 5, 0 addition for the reason explained after the bolded area.

American hops are perfect for American IPAs. I don't know what you mean about not using them!
 
ArcaneXor said:
In an American IPA? Centennial and Amarillo are *awesome* for aroma and dry hopping. Plus the AA% of late additions doesn't really matter all that much unless you whirlpool/hot steep for a while. If you knock the temperature down to below ~180 degrees within 5 minutes, the difference in additional bittering imparted by a 4% AA and a 10% AA flameout hop is very small.
Click to expand...

Actually, to get a bit geeky about the hops, it's not the high AAU (and 10% isn't high!) but it's actually the makeup of the hops themselves, specifically the cohumulone/humulone content. Higher cohumulone hops are considered by many to be "harsh" while low cohumulone hops are considered less so, regardless of the AAUs of the hops. In theory, that could mean that an 18% AAU hop variety could be less harsh than a 4.8% AAU variety. So, it's not just the AAUs that must be considered, but the actual properties of the hops variety.

American IPAs use American hops (and occasionally an English variety) for late hopping. This usually gives a resiny/citrusy/floral finish but "earthy" hops are used also. That's what an American IPA is all about. It would be very odd to use noble hops for finishing an American IPA.
 
+1, and just to add to that, %AAs have nothing to do with the amount of aroma/flavor a hop provides either.
 

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