connection between efficiency and IBU

[Elysium]

I am working on my second recipe and I am experimenting with different efficiency rates and the IBU keeps changing as I adjust it. (I am using brewtoad).

If efficiency is at 65%, the IBU is at 39 (that's what I am aiming for). If it is 75%, then it changes to 36. I am wondering if the 3 IBU will make a big difference in the bitterness and if there is a way to keep my IBU constant?

 

[GrogNerd]

IIRC, hops utilization is dependent upon the gravity of the wort, which is dependent upon the efficiency

 

[Mojzis]

I believe we can only sense changes in IBU's over three, but I am no expert. Your IBU's are changing because your efficiency changes the amount of fermentable sugars in the wort. Higher efficiency means more sugars, more sugars means slightly stronger beer. A stronger beer (sometimes said to be more malty) needs more bitterness to combat or equalize the sweetness of the wort. This all plays with issomerization rates (along with time, temp, gravity, etc).

Ways to keep IBU's constant:

Keep track of the age of the hops, older hops are less bitter.

Pellet hops and leaf hops may have different issomerization rates, you may adjust accordingly.

Keep the boil rolling, and the same every time.

Dial in your process so you know what efficiency you can expect. This is huge for several reasons besides IBU's. Try looking at some of the posts and stickies on how to raise and maintain efficiency.

Edit: IMO a change of 3 IBU's will not be detected.

 

[Elysium]

Dial in your process so you know what efficiency you can expect. This is huge for several reasons besides IBU's. Try looking at some of the posts and stickies on how to raise and maintain efficiency.

Edit: IMO a change of 3 IBU's will not be detected.

Thanks for the reply. There is another thing that concerns me now....after reading your reply.

I have just made MO+Saaz (SMaSH) and set the IBU at 39. Meaning that it is going to be extra hoppy...from a hop type that is used in lager. Do you think the taste of my brew will be totally unpleasant?And would you say that most of the people go for the evenly balanced way if they dont like very bitter beers?

 

[Yooper]

Thanks for the reply. There is another thing that concerns me now....after reading your reply.

I have just made MO+Saaz (SMaSH) and set the IBU at 39. Meaning that it is going to be extra hoppy...from a hop type that is used in lager. Do you think the taste of my brew will be totally unpleasant?And would you say that most of the people go for the evenly balanced way if they dont like very bitter beers?

There are a couple of things to be aware of. First, the reason the IBUs change when you change your efficiency isn't so much that IBUs are dependent on wort gravity (it's not, it's more "break material" per John Palmer) but that your SG/IBU ratio changes slightly, so it takes more bittering to "cover" the extra bit of sweetness.

I hope that makes sense. Think of it this way. Say you had a beer with an OG of 1.050 and 50 IBUs. That will be firmly bitter (an IBU/SG ratio of 1.000). If you had a beer with an OG of 1.039, 50 IBUs would be undrinkably bitter (IBU/SG ratio of 1.29!), and if you had an OG of 1.099, 50 IBUs would be on the sweet side (ratio of .325!).

In other words, by itself, the IBU number is meaningless. 50 IBUs may be a lot, or it may not be enough. In a blonde ale, it'd be way too much. In a RIS, it wouldn't be enough.

In the case where you're asking about 36 vs 39 IBUs, the difference is negligible. The human tongue probably can't perceive differences of 5 IBUs or so. But it depends on the beer- in a 12 IBU beer, 5 IBUs is alot. In a 40 IBU beer, it's not.

If your IBU/SG ratio is in the ballpark for the beer style you're making, then it will be fine. The key is balance. With the IBU scale, it's helpful to look at those IBUs. But you have to consider the beer style and what IBUs need to be to balance the sweet malt properly.

 

[Elysium]

There are a couple of things to be aware of. First, the reason the IBUs change when you change your efficiency isn't so much that IBUs are dependent on wort gravity (it's not, it's more "break material" per John Palmer) but that your SG/IBU ratio changes slightly, so it takes more bittering to "cover" the extra bit of sweetness.

I hope that makes sense. Think of it this way. Say you had a beer with an OG of 1.050 and 50 IBUs. That will be firmly bitter (an IBU/SG ratio of 1.000). If you had a beer with an OG of 1.039, 50 IBUs would be undrinkably bitter (IBU/SG ratio of 1.29!), and if you had an OG of 1.099, 50 IBUs would be on the sweet side (ratio of .325!).

In other words, by itself, the IBU number is meaningless. 50 IBUs may be a lot, or it may not be enough. In a blonde ale, it'd be way too much. In a RIS, it wouldn't be enough.

In the case where you're asking about 36 vs 39 IBUs, the difference is negligible. The human tongue probably can't perceive differences of 5 IBUs or so. But it depends on the beer- in a 12 IBU beer, 5 IBUs is alot. In a 40 IBU beer, it's not.

If your IBU/SG ratio is in the ballpark for the beer style you're making, then it will be fine. The key is balance. With the IBU scale, it's helpful to look at those IBUs. But you have to consider the beer style and what IBUs need to be to balance the sweet malt properly.

I am trying to understand the ratio idea you have just explained here...but I am clue less...for example, OG:1.039 IBU: 50..how does that give IBU/SG ratio 1.29?

 

[Yooper]

I am trying to understand the ratio idea you have just explained here...but I am clue less...for example, OG:1.039 IBU: 50..how does that give IBU/SG ratio 1.29?

50:39

It's a ratio.

 

[NordeastBrewer77]

There are a couple of things to be aware of. First, the reason the IBUs change when you change your efficiency isn't so much that IBUs are dependent on wort gravity (it's not, it's more "break material" per John Palmer) but that your SG/IBU ratio changes slightly, so it takes more bittering to "cover" the extra bit of sweetness.

I hope that makes sense. Think of it this way. Say you had a beer with an OG of 1.050 and 50 IBUs. That will be firmly bitter (an IBU/SG ratio of 1.000). If you had a beer with an OG of 1.039, 50 IBUs would be undrinkably bitter (IBU/SG ratio of 1.29!), and if you had an OG of 1.099, 50 IBUs would be on the sweet side (ratio of .325!).

In other words, by itself, the IBU number is meaningless. 50 IBUs may be a lot, or it may not be enough. In a blonde ale, it'd be way too much. In a RIS, it wouldn't be enough.

In the case where you're asking about 36 vs 39 IBUs, the difference is negligible. The human tongue probably can't perceive differences of 5 IBUs or so. But it depends on the beer- in a 12 IBU beer, 5 IBUs is alot. In a 40 IBU beer, it's not.

If your IBU/SG ratio is in the ballpark for the beer style you're making, then it will be fine. The key is balance. With the IBU scale, it's helpful to look at those IBUs. But you have to consider the beer style and what IBUs need to be to balance the sweet malt properly.

Thanks, I would've needed three times as many words to describe that half as well.

I am trying to understand the ratio idea you have just explained here...but I am clue less...for example, OG:1.039 IBU: 50..how does that give IBU/SG ratio 1.29?

It's a simple ratio; bitterness units:gravity units (points). A beer with 50 gravity points (1.050) and 50 IBU is a 1:1 ratio, or a BU:GU ratio of 1. That's hoppy. A balanced beer will be closer to a BU:GU ratio of .5, so say a 1.050 (50 points) with 25 IBU. To put it in palate terms, things like IPA will tend have a BU:GU ratio over 1.00, while malty beers tend to have a BU:GU ratio below .5.

 

[GrogNerd]

There are a couple of things to be aware of. First, the reason the IBUs change when you change your efficiency isn't so much that IBUs are dependent on wort gravity (it's not, it's more "break material" per John Palmer) but that your SG/IBU ratio changes slightly, so it takes more bittering to "cover" the extra bit of sweetness.

I guess I do have to argue with Yooper

as per Palmer

To calculate how much bitterness the final beer will have from these hop additions, we apply factors for the recipe volume (V), gravity of the boil and the boil time. The time and gravity of the boil are expressed as the utilization (U). The equation for IBUs is:

IBU = AAU x U x 75 / Vrecipe

 

[NordeastBrewer77]

I guess I do have to argue with Yooper

as per Palmer

He's stated otherwise numerous times since the first edition of HTB. He's even pointed out that he was incorrect in stating that in HTB, IIRC.

 

[GrogNerd]

then I'll reference tinseth

 

[NordeastBrewer77]

then I'll reference tinseth

As will I:

...... Your experience and brewing practices may be different than mine so here's the official disclaimer: Your Mileage May Vary (YMMV). ......

Not that I disagree, but I think the jury is largely out on the subject. MMVed, and I've seen very little difference in extract batches where the extract was not in the boil when compared to the same recipe with the extract boiled for the duration. As I stated in my first post, I've done the side by sides. That said, as an AG brewer that uses software to design recipes, wort gravity is always considered when creating the hop profile.

 

[Yooper]

I guess I do have to argue with Yooper

as per Palmer

Right, I know. But in 2008, Palmer said he "got it wrong" in How to Brew, and he's been talking about it on podcasts, articles, etc, as well as the NHCs that I've been to where we've talked about it in person.

Glenn Tinseth also talks about it.

There are LOTS of sources post-2008 (easily found on google) that discuss this, if you're interested.

The thing is, though- regardless of the cause of hops utilization, the formula sort of works anyway. It's not accurate, and the only way to really know the IBUs would be to have them tested, but it's the best we have to guestimate the bittering of the beer.

For example, Pliny the Elder has a theoretical IBU of something like 239 using the Tinseth scale. But it's been actually lab tested at something like 85.

That doesn't really matter- because we'd all call that beer "hoppy" anyway!

But that's the point with IBUs. It's not an exact science, and far more goes into hops utilization than wort gravity, break material, etc. Even for scientists, it's still not well understood.

And the argument I have with the above chart has "hoppy" as a description. I've had lots and lots of 50+ IBU beers that aren't hoppy at all. It's "bitterness" that you can measure. You can't measure "hoppy" because that's a flavor/aroma that contributes very little to the IBUs. You can have a beer that has 20 IBUs that has a ton of hops flavor and aroma.

 

[GrogNerd]

good stuff.

regardless, the recipe software takes gravity into account in calculating IBU. that's why it changes when efficiency changes.

can anyone reference an IBU calculator that doesn't use gravity as a variable?

and agree with Mojzis, at least to my palate, the 3 IBU difference would be undetectable

navy chow destroyed my palate, I'm sure I couldn't detect a 30 IBU difference

 

[NordeastBrewer77]

good stuff.

regardless, the recipe software takes gravity into account in calculating IBU. that's why it changes when efficiency changes.

can anyone reference an IBU calculator that doesn't use gravity as a variable?

and agree with Mojzis, at least to my palate, the 3 IBU difference would be undetectable

I'm not sure that there is one. That's what I was getting at in my last post. We all use software to design recipes, right? Or at least we should be. The software is going to figure in boil gravity when calculating IBUs. And like Yooper said, unless we're sending samples off to a lab, that IBU number is a guesstimate at best. It's pretty much a guideline for us to use when designing a beer recipe.

 

[Mojzis]

First, the reason the IBUs change when you change your efficiency isn't so much that IBUs are dependent on wort gravity (it's not, it's more "break material" per John Palmer) but that your SG/IBU ratio changes slightly, so it takes more bittering to "cover" the extra bit of sweetness.

On a few books I have read, the list of variables that affect utilization/isomerization is indeed plentiful. Gravity was one variable. That's all I meant.

He's stated otherwise numerous times since the first edition of HTB. He's even pointed out that he was incorrect in stating that in HTB, IIRC.

Yeah I don't go by Palmer alone anymore, I have run across a few things that have been dis-proven or that he has stated were incorrect.

And the argument I have with the above chart has "hoppy" as a description. I've had lots and lots of 50+ IBU beers that aren't hoppy at all. It's "bitterness" that you can measure. You can't measure "hoppy" because that's a flavor/aroma that contributes very little to the IBUs. You can have a beer that has 20 IBUs that has a ton of hops flavor and aroma.

Fully agree. The chart has limited use, but it shows the relationship between IBU's and gravity. I would have preferred it if the chart said bitter instead of hoppy.