Calculation of IBU additions after flame out (no chill/whirlpool)

[lael]

Scotty,how long are you whirlpooling / having hop and wort contact to see those utilisation rates?

 

[Midnight Brew]

Just to throw in some discussion, I currently calculate my cube hop addition as a 20 minute boil addition.

I've measure my wort 20 minutes after flameout with lid on and got 97C. Then I whirlpooled and waited 40 minutes with the lid on and got 95C. That is what I base my guesstimates at. Having a read of your article RB I'm now thinking I havnt measured my wort after transfer to the cube and Im going to say there would be a few additional degrees lost in that transfer itself, so I could realistically have wort at 90 - > 95C. (I'll measure this heat loss next brew)

Had a quick browse at the beersmith software and the default steep utilisation is 50% assuming that the wort is at the default temperature of 90C (at least 90C is recommended).

Went back and had a play with a few recipes already brewed and its literally half of what I have been estimating at. In one example its gone from 14IBU at cube hop to 7IBU. Now Im not sure whether I could detect 7IBU difference unless that samples were side by side. Sure does make for an interesting formulation of how we design our beers. Id love to be able to actually measure the IBU in a beer.

 

[///]

Whirlpool for 10, sit for 5, then run off in 45.

For the high alpha Aussie hops, they fry off really quick. Hence why we dry hop alot and hold right back on the bittering. I am also lucky that with the colandria it helps to manage the boil, remember hops help to reduce boil overs.

 

[technobabble66]

Hey III, apologies for being a bit of a thicker, but just to clarify, are you saying it takes you 45mins to drain your kettle?

 

[jyo]

/// is a commercial brewer, mate. He's talking 1000's of litres

This is great discussion. Top work, relaxedbrewer. With APA / IPA and high alpha hops I've learned the hard way (and from reading ///'s posts in the past about this) to be more aware of the bittering contributions of whirlpool hops. It will be cool to have a simple formula to help calculate.

Cheers.

 

[///]

Yep sorry, on average we have about 2100l in the whirlpool, but follow the same principles at home. Also one year made about 30000l of wort packs for another business and followed the same principles.

 

[pat86]

Very interesting, thanks OP. Scotty if you or the YH guys made fresh wort, they would definitely be the first fresh wort kits I would want to buy!

 

[RelaxedBrewer]

OK, I have done a second draft of the article.
I have included an example brew I did and some example utilisations from different chilling techniques. I also cleaned a few things up.

I understand that this article may go over some peoples heads (most people are not going to understand the maths, I know it took me a little while to get my head around at first). So if you don't want to read the article I will summarise it.
In summary;
1) I have derived an equation that can be used to estimate alpha acid utilisation and therefore IBUs with changing temperatures.
2) This can be used for estimating IBUs from whirlpool/hop stand and no chill additions.
3) This work was an extension of some other peoples work published in per reviewed scientific journals.
4) I have given examples of my no chill technique and the utilisations I expect on my system for different hop additions after flame out.
5) I applied this technique to a big hoppy West Coast IPA style recipe and showed the IBUs I expected from each hop addition.
6) I also have given some examples of utilisations from a few other techniques/systems.
7) I don't have access to equipment to test for alpha acids and there can not get actual IBU values. I am probably going to try to contact a university and see if anyone is interested in this work and try to check with real world values. If this happens we would most likely produce a proper scientific paper.

View attachment nochillwhirlpoolIBUutilizationcalculation-3.pdf

 

[danestead]

OK, I have done a second draft of the article.
I have included an example brew I did and some example utilisations from different chilling techniques. I also cleaned a few things up.

I understand that this article may go over some peoples heads (most people are not going to understand the maths, I know it took me a little while to get my head around at first). So if you don't want to read the article I will summarise it.
In summary;
1) I have derived an equation that can be used to estimate alpha acid utilisation and therefore IBUs with changing temperatures.
2) This can be used for estimating IBUs from whirlpool/hop stand and no chill additions.
3) This work was an extension of some other peoples work published in per reviewed scientific journals.
4) I have given examples of my no chill technique and the utilisations I expect on my system for different hop additions after flame out.
5) I applied this technique to a big hoppy West Coast IPA style recipe and showed the IBUs I expected from each hop addition.
6) I also have given some examples of utilisations from a few other techniques/systems.
7) I don't have access to equipment to test for alpha acids and there can not get actual IBU values. I am probably going to try to contact a university and see if anyone is interested in this work and try to check with real world values. If this happens we would most likely produce a proper scientific paper.

That is really bloody awesome that you have gone to the effort of doing the research and experimentation and summaried your findings. It seems it has been a big unknown - until maybe now!

I used to think I was reasonable considering I did double maths at school however the equations are getting a little confusing to me. I've worked on a couple of rules of thumb that I've read online for isomerisation at temperatures other than 100c so it'd be great if I could compare those rules to your equations answers.

It looks like in your paper that the utilisation of hops varies with the gravity of the wort. This was always considered the case I believe however John Palmer has changed his thoughts on that and has written somewhere (maybe an updated 'How to Brew' book - I'm not sure) that there is no evidence that this happens. It'd be interesting to hear your thoughts on that and maybe if you have the equipment to test IBU's, you could test a few different wort gravities vs utilisation. Anyway that is slightly off topic.

What I'm asking is, are you able to show me how I use your equation to calculate how many IBU's I will extract for the following 2 situations.

I have used Promash to calculate a 15min addition and the calculated IBU's.

1.050 OG wort
20g of Citra (10% AA) for 15mins
(Note: I'm not sure what the iso-a-acidt vs a-acid0 is but if it refers to the degradation of the AA% of hops over time in storage, lets say that the Citra was 12% AA to begin with and has been stored for a while in the freezer to end up at 10% AA now)

Promash gives me 22.5 IBU's based on Tinseth and a boil addition (100c)
My rule of thumb is that at 90c you halve the IBU's as compared to a 100c addition and that at 75c it is about 10-15% of the 100c amount, therefore:

@ 90c for 15min I estimate 11.25 IBU's
@ 75c for 15min I estimate 2.25-3.375 IBU's


How does your equation compare and can you show your working so I can later do it myself. Lets assume the temp is kept constant at 90 and 75 deg.

Cheers.

 

[RelaxedBrewer]

@danestead I will run though it for you after the weekend (I have a rather big one with the VIC case swap).

Your rule of thumb seems like a pretty good estimate though.

 

[RelaxedBrewer]

@ 90c for 15min I estimate 11.25 IBU's
@ 75c for 15min I estimate 2.25-3.375 IBU's

How does your equation compare and can you show your working so I can later do it myself. Lets assume the temp is kept constant at 90 and 75 deg.

In the situation you are proposing we are holding the temperature constant and you do not even need most of the work I have done. I have made equations that will work with changing temperatures something that other have not done yet (as far as I am aware).

So for your case we can use existing formula.
To get utilisation we use
U = 1- e^(-kt) (equation 2 in my article).
and k is temperature dependent
k = Ae^(-E/RT) (equation 2 in my article).
The constants A and E/R were solved by experimentation in the second paper I listed (JASKULA, B. KAFARSKI, P AERTS,G. COOMAN, L. A Kinetic Study on the Isomerization of Hop r-Acids J. Agric. Food Chem. 2008, 56, 6408–6415)
and were found to be A=3.13*109 and E/R=11661.

So for your situation all you need to do is plug in the temperature (T), A and E/R into the equation for k.(note: T is in Kelvin)
Then once you have k plug that into the utilisation equation with the time and find U (note t is in seconds).

So for 15 min @ 90C we get U = 7.2%
This equates to an IBU of 8.

and for 15 min @ 75C we get U = 0.8%
This equates to an IBU of 0.8

So your estimates are higher than mine.
I have never used promash, does it give utilisations for hop additions as well as IBUs? The brewing software I have gives 13 IBUs and a 12 U for a 15 min boil (100C) addition of 10AA Citra in 50 OG wort. This is a lot different from what you say Promash is giving you (22.5 IBU). What batch size are you doing and what boil size? (The number I quoted above are for 19L with a 23L pre boil volume)


(The interesting thing that I have done is modify this above method to work with a changing temperature by using some calculus and time series estimations)

 

[danestead]

Thanks for such a detailed post!

Im on holidays so dont have promash infront of me however im pretty sure it only gives an IBU number. Whilst we are talking about utilisation, when you say that in my 90 degree example there is 7.2% utilisation, to get 8 IBU's are you just rounding up or is the utilisation multiplied by the hop AA%?

The batch size I was using was 25L however that is actually my post-boil volume. I always use my post boil volume as batch size and use my efficiency as a mash efficiency. I manually calculate my losses rather than calling my batch 21L (volume into fermenter) and inputting my losses to kettle, trub, shrinkage into the software for it to calculate it all automatically. Preboil volume on my 25L 'batch' would usually be 28.1L for a 60min boil.

 

[Forever Wort]

I heard about this article at the Merri Mashers meeting last night. This is valuable and great work Kris.

For the less mathematically-minded among us brewers, all I can say is keep at it and hopefully we will one day see an accurate software calculator that will be able to give us estimated no-chill IBU additions based on simple variables we can input ourselves (gravity, AA, cooling times).

 

[verysupple]

In the situation you are proposing we are holding the temperature constant and you do not even need most of the work I have done. I have made equations that will work with changing temperatures something that other have not done yet (as far as I am aware).

So for your case we can use existing formula.
To get utilisation we use
U = 1- e^(-kt) (equation 2 in my article).
and k is temperature dependent
k = Ae^(-E/RT) (equation 2 in my article).
The constants A and E/R were solved by experimentation in the second paper I listed (JASKULA, B. KAFARSKI, P AERTS,G. COOMAN, L. A Kinetic Study on the Isomerization of Hop r-Acids J. Agric. Food Chem. 2008, 56, 6408–6415)
and were found to be A=3.13*109 and E/R=11661.

So for your situation all you need to do is plug in the temperature (T), A and E/R into the equation for k.(note: T is in Kelvin)
Then once you have k plug that into the utilisation equation with the time and find U (note t is in seconds).

So for 15 min @ 90C we get U = 7.2%
This equates to an IBU of 8.

and for 15 min @ 75C we get U = 0.8%
This equates to an IBU of 0.8

So your estimates are higher than mine.
I have never used promash, does it give utilisations for hop additions as well as IBUs? The brewing software I have gives 13 IBUs and a 12 U for a 15 min boil (100C) addition of 10AA Citra in 50 OG wort. This is a lot different from what you say Promash is giving you (22.5 IBU). What batch size are you doing and what boil size? (The number I quoted above are for 19L with a 23L pre boil volume)


(The interesting thing that I have done is modify this above method to work with a changing temperature by using some calculus and time series estimations)

I've been playing around with this and I think you may have made a mistake.

For 15 min at 90 C. I get U = 3.1 % (which matches Table 2 in Jaskula et al, you got 7.2 %) and for 15 min at 75 C I get U = 0.8 % (the same as you).

Other than that, great find!

 

[technobabble66]

...

So for 15 min @ 90C we get U = 7.2%
This equates to an IBU of 8.

and for 15 min @ 75C we get U = 0.8%
This equates to an IBU of 0.8

So your estimates are higher than mine.
I have never used promash, does it give utilisations for hop additions as well as IBUs? The brewing software I have gives 13 IBUs and a 12 U for a 15 min boil (100C) addition of 10AA Citra in 50 OG wort. This is a lot different from what you say Promash is giving you (22.5 IBU). What batch size are you doing and what boil size? (The number I quoted above are for 19L with a 23L pre boil volume)


(The interesting thing that I have done is modify this above method to work with a changing temperature by using some calculus and time series estimations)

Might need to check this Kris. I think for 90mins, U = 3.1%

Edit - curses for not refreshing my page, very supple beat me to it!

Again - Great paper!
We (ie: you ) just need to organise a quick little spreadsheet where a brewer can do a quick few temp checks, get a rough estimate of the cooling rate for their kettle/cube, then plug in a time to get a whirlpool/cube Utilisation estimate; and hence by-pass having to do the calculations themselves.

Edit 2: I think Kris used 100°C in his calc's instead of 90°C. No biggie.

 

[RelaxedBrewer]

Yeah.. sorry I sorted that stuff out via PMs. I accidentally listed the 100C calculation as the 90C, I should have updated the post.

A quick update: I spoke to a professor from RMIT alst week. He is quite interested in this kind of work. He is busy with other work for the next month or so but was pretty keen to collaborate with me after. This means I should be able to take some measurements and check the formula against real world data some time in the near future.

 

[Byran]

My advise to no chill brewers is to remove any 'mid' additions, ie. hops at 15, 10, 5 minutes, and just utilise the whirlpool with a standard amount taken from the step.

Not sure if I would drop the temp and then fill the no-chill container, i would go as hot as possible to maximise the pasteurization units particularly if you are reusing the container.

After much experimentation with no chill I have basically ended up in this exact scenario. On some lighter beers I only do a whirlpool addition. It feels weird to not boil any hops but it works.

 

[tateg]

Hi Guys
I am just trying to work the above equations out of curiosity but cant seem to get it going.
for the below scenario can someone tell me the actual equation using the data

So for 15 min @ 90C we get U = 7.2%
This equates to an IBU of 8.

U = 1- e^(-kt) (equation 2 in my article).
and k is temperature dependent
k = Ae^(-E/RT) (equation 2 in my article).

I understand what the values mean just not sure about how to enter them

thanks

 

[danestead]

Hi Guys
I am just trying to work the above equations out of curiosity but cant seem to get it going.
for the below scenario can someone tell me the actual equation using the data

So for 15 min @ 90C we get U = 7.2%
This equates to an IBU of 8.

U = 1- e^(-kt) (equation 2 in my article).
and k is temperature dependent
k = Ae^(-E/RT) (equation 2 in my article).

I understand what the values mean just not sure about how to enter them

thanks

Try PM relaxedbrewer. He originally had some small typos to the formulas he wrote up however will be able to help you out via PM to sort out your problem.