IBU Formulas Help

[Hawaiibboy]

So I have been using iBrewmaster for a little while and never noticed this before:

If I change my grain bill, my IBUs change. I am using the tinseth formula.

From other posts I have read, tinseth is best for BIAB, but my question is if the IBUs are supposed to change if my grain bill changes?

Note: I am doing nothing to my hops schedule or amount.

 

[gcdowd]

Yes, hop utilization is impacted by the gravity of the wort

 

[Hawaiibboy]

Yes, hop utilization is impacted by the gravity of the wort

Good to know! I couldn't find it in my two books or anything and it was bothering me! Lol

 

[gcdowd]

Sure thing. That is why there is always a lot of talk about doing full boils vs. partial boils and how the IBUs are affected. Same thing with late LME/DME additions.

 

[rklinck]

If you are interested, Palmer's How to Brew includes a chart that sets out the utilization based on the length of the boil and the gravity of the wort.

 

[Yooper]

Actually, it's been since about 2008 that it's been disproven that wort gravity impacts hops utilization. It really doesn't, and John Palmer stated that he "got it wrong" in How To Brew.

It's now thought that break material may impact utilization but that's just a theory.

 

[rklinck]

Actually, it's been since about 2008 that it's been disproven that wort gravity impacts hops utilization. It really doesn't, and John Palmer stated that he "got it wrong" in How To Brew.

It's now thought that break material may impact utilization but that's just a theory.

So are you saying that we will get the same IBUs regardless of OG? Or are you saying that something is going on but we aren't sure what is causing the difference in IBUs?

 

[Hawaiibboy]

Actually, it's been since about 2008 that it's been disproven that wort gravity impacts hops utilization. It really doesn't, and John Palmer stated that he "got it wrong" in How To Brew.

It's now thought that break material may impact utilization but that's just a theory.

So then what formula should be used to take this into account? Rager?

 

[Yooper]

So then what formula should be used to take this into account? Rager?

I still use Tinseth, but just recognize that some of the issues with all of the IBU calculators simply mean it's not always right. At best, it's a good guess.

Whatever one you use, Tinseth or Rager, just always use the same one so you know what "50 IBUs" on your system tastes like to you. Unless you actually get it tested, you really have no other idea.

I was doing some reading about this recently, and even Pliny the Elder, which calculates out to something like 250 IBUs was tested by a lab and the IBUs were actually something like 75!

 

[Calder]

Actually, it's been since about 2008 that it's been disproven that wort gravity impacts hops utilization. It really doesn't, and John Palmer stated that he "got it wrong" in How To Brew.

It's now thought that break material may impact utilization but that's just a theory.

I don't believe it has been proven/dis-proven. It is still a subject of debate.

If it were now an established 'fact' that boil gravity did not affect utilization; such a major change in thought to the established beliefs (and known since 2008), I suspect Stan Hieronymus would have noted that significant discovery in his recent book 'HOPS' (originally published 2012). Stan doesn't mention that to even be a possible change in the current thought process for hop utilization and in the book says "Utilization decreases as wort gravity increases" (Page 188).

 

[Hawaiibboy]

I still use Tinseth, but just recognize that some of the issues with all of the IBU calculators simply mean it's not always right. At best, it's a good guess.

Whatever one you use, Tinseth or Rager, just always use the same one so you know what "50 IBUs" on your system tastes like to you. Unless you actually get it tested, you really have no other idea.

I was doing some reading about this recently, and even Pliny the Elder, which calculates out to something like 250 IBUs was tested by a lab and the IBUs were actually something like 75!

Good info there! I have known about the limits of IBU's in a beer and so the thing that always confused me was how people got like 100+IBUs but the formulas only provide a potential contribution to the beer and act as a way to estimate flavors.