ATTENTION: All Partial Boil Brewers - Page 2

jkarp · 12-03-2008, 04:59 PM

A lot of nice work, but it still flies in the face of the results from the 2007 International Brewers Symposium. There's a LOT more variables to IBU production than wort volume. Sure would be nice if a simple test for calculating isomerized AA in finished beer were available so we could validate. Hell even the Tinseth table could use a proper vetting IMO.

**FlyGuy** · 12-03-2008, 05:14 PM

Quote:

Originally Posted by jkarp

A lot of nice work, but it still flies in the face of the results from the 2007 International Brewers Symposium. There's a LOT more variables to IBU production than wort volume. Sure would be nice if a simple test for calculating isomerized AA in finished beer were available so we could validate. Hell even the Tinseth table could use a proper vetting IMO.

If you are going to disagree, can you also provide the details? I am not sure what you are referring to by stating "it flies in the face of the results from the 2007 International Brewer's Symposium". Sometimes 'a lot of variables' in an equation also boils down to 'a few that are imortant'.

And actually, there is a very simple test for measuring isomerized alpha acids in wort -- it just requires access to a chemistry lab!

Cheers.

**FlyGuy** · 12-03-2008, 05:23 PM

Also to the OP, no offense intended here, but what is different about your formula than the standard calculation of IBUs that people have used for a long time? One would normally compute the IBU contribution of each hop addition independently, based on the gravity of the wort anyways, and then add them up to get a total. Isn't that what you did here, or am I missing something? (Sorry if I am being thick.)

**BarleyWater** · 12-03-2008, 06:35 PM

Quote:

Originally Posted by FlyGuy

Also to the OP, no offense intended here, but what is different about your formula than the standard calculation of IBUs that people have used for a long time? One would normally compute the IBU contribution of each hop addition independently, based on the gravity of the wort anyways, and then add them up to get a total. Isn't that what you did here, or am I missing something? (Sorry if I am being thick.)

Nothing different really, except the last part, which takes into account the boil volume and a dilution factor that no other formulas take into account. If you boil the full volume, this formula is just like Palmer's and similar to Daniels', but if you top off with plain water, this will get you the amount of IBU's left after dilution.

jkarp, were you at the symposium? Probably not. Can you give me any of the other variables, or your equation for figuring out bitterness? Saying it "flies in the face" of anything is a bold statement, and you have backed it up with nothing. I heard your argument in the other thread, and it wasn't a very good one. I listened to the podcast you posted, and it certainly doesn't help your case at all with Palmer stating that the way we do things now is just fine for us homebrewers, and easily close enough to be considered fairly accurate. If you want to argue that's fine, but at least have something to back up what you have to say. I understand things like protien percentage, yeast floculation and even oxidized beta acids in older hops can all affect bitterness, and malt types and gravities affect bitterness perception, but there is no way of effectively measuring that because it varies widely from batch to batch. Even with the same recipe it can swing depending on how the yeast work through the wort, and probably even what the weather is like that week.

There are so many other variables to consider, but when Master Brewers at AB, John Palmer, and other reasearch scientists have found that our current calculations get us pretty close, I think it's ok to use them. Palmer stated after attending the symposium in question, that even he didn't understand fully what was going on (very technical stuff), and that a lot more research into hops needs to be done, because there isn't much out there. What he did conclude was that our current system of measurement may not be perfect, but it gets us pretty darn close, and as a homebrewer do we really need to be anything more than pretty darn close. Those other variables are there, but way too hard to quantify, and correction factors are built into the equation. Once you figure out your system and know what a certain amount of IBUs is supposed to taste like, it is fairly easy using the available formulas and info to craft a great recipe, every brewery in the world does it, and mine helps out people adding top off water to their batch post boil.

**FlyGuy** · 12-03-2008, 09:13 PM

OK, I think I understand what you have done. You are trying to correct for the dilution effect on IBUs. I have some suggested improvements here.

There is a small but significant flaw in your thinking -- the dilution effect is only relevant to the calculation of the theoretical MAXIMUM IBUs obtained in your boil. For recipes that don't exceed this maximum in the boil kettle, no dilution correction is necessary -- i.e. you don't need your formula, just use the conventional calculations. For example, look at the example Palmer provides in "How to Brew" he actually walks you through a partial boil. It is a 5 gal recipe with a 3 gal boil. He uses the method I mentioned in my previous post (i.e. figure out the utilization and resulting IBUs at each addition and sum them up for total IBUs in the batch).

Hoppy beers:

Now, let's consider a large hop addition where you might actually hit that maximum limit for isomerized alpha acids.

In this situation, you should calculate the IBUs for the boil (not the recipe) first to check if you are exceeding the theoretical maximum IBUs. The computation is exactly the same as what Palmer describes, except that we will use the boil volume, not the recipe volume for this calculation:

IBU = Sum[ (AAU * U * 74.89) / Vb ]

If the result exceeds the theoretical maximum IBUs (e.g., 100), then bitterness of this recipe is going to be stunted by the dilution. To determine the resulting bitterness of the recipe, the following formula can be used:

IBU = AAmax * Vb / Vr

where AAmax is your theoretical limit to AA extraction (e.g., 100 IBU).

Example:

To illustrate using your example with two BIG hop additions and a 2.5 gal boil volume, here is what we get:

boil IBU = Sum[ (AAU * U * 74.89) / Vb ]
= [(26*0.231*74.89/5)+(12*0.084*74.89/5)]
= 210

That exceeds the AAmax of 100 IBU, so the recipe is going to also be limited to the following bitterness:

recipe IBU = AAmax * Vb / Vr
= 100 * 2.5 / 5
= 50

I think this was what you were trying to achieve in your formula (note the common term Vb/Vr in both your and my equations). Hope that made sense.

I'll try to write this up in a new post along with a quick spreadsheet to do the calculations given to clean up the presentation.
Cheers!

jkarp · 12-03-2008, 09:22 PM

Quote:

Originally Posted by BarleyWater

jkarp, were you at the symposium? Probably not. Can you give me any of the other variables, or your equation for figuring out bitterness? Saying it "flies in the face" of anything is a bold statement, and you have backed it up with nothing. I heard your argument in the other thread, and it wasn't a very good one. I listened to the podcast you posted, and it certainly doesn't help your case at all with Palmer stating that the way we do things now is just fine for us homebrewers, and easily close enough to be considered fairly accurate. If you want to argue that's fine, but at least have something to back up what you have to say. I understand things like protien percentage, yeast floculation and even oxidized beta acids in older hops can all affect bitterness, and malt types and gravities affect bitterness perception, but there is no way of effectively measuring that because it varies widely from batch to batch. Even with the same recipe it can swing depending on how the yeast work through the wort, and probably even what the weather is like that week.

No need to get your panties in a wad. You've just done an excellent job right here in your own quote explaining my point. I'm simply saying that brewers are kidding themselves by using this formula to calculate IBUs to the nth significant digit. There's more to it than wort volume and a number out of a table. QED.

**FlyGuy** · 12-03-2008, 10:01 PM

Quote:

Originally Posted by jkarp

No need to get your panties in a wad. You've just done an excellent job right here in your own quote explaining my point. I'm simply saying that brewers are kidding themselves by using this formula to calculate IBUs to the nth significant digit. There's more to it than wort volume and a number out of a table. QED.

I feel it is unfortunate that you are being critical without being constructive.

I have always found this to be a very supportive community that follows in the spirit of helping one another. If you are going to criticize someone, I am sure you will get a more favorable response if you are either more constructive in your comments or you at least back up your criticisms.

jkarp · 12-03-2008, 10:17 PM

No criticism was made nor implied FlyGuy. As far as being constructive, the information from the Brewers Symposium, along with links to John Palmer's report on it has been discussed in several different threads here over recent months. I'm sorry you missed them, but it should be an easy search.

There was nothing in my OP that was un-supportive. I simply lamented the fact that we don't have a simple IBU test as it would make fine-tuning IBU calculations (the original goal of this thread) much easier and allow the numerous complicating factors BarleyWater pointed out to be tested and taken into account.

**BarleyWater** · 12-04-2008, 04:13 AM

Quote:

Originally Posted by FlyGuy

OK, I think I understand what you have done. You are trying to correct for the dilution effect on IBUs. I have some suggested improvements here.

There is a small but significant flaw in your thinking -- the dilution effect is only relevant to the calculation of the theoretical MAXIMUM IBUs obtained in your boil. For recipes that don't exceed this maximum in the boil kettle, no dilution correction is necessary -- i.e. you don't need your formula, just use the conventional calculations. For example, look at the example Palmer provides in "How to Brew" he actually walks you through a partial boil. It is a 5 gal recipe with a 3 gal boil. He uses the method I mentioned in my previous post (i.e. figure out the utilization and resulting IBUs at each addition and sum them up for total IBUs in the batch).

This is my point right here, Plamer has a small but significant flaw in HIS equation. He states on that page...

Quote:

But, since we are only boiling 3 of the 5 gallons due to of the size of the pot, we need to take into account the higher gravity of the boil. The boil gravity becomes 6 x 40 / 3 = 80 or 1.080

He goes on to use this number, 1.080, to formulate the rest of the recipe using Tinseth's formula which is not intended for partial boil brews, and he does not take into account the wort being diluted by water after the boil, only the higher gravity of the boil. The sample he gave resulted in 31.2IBUs, but really should have been 15.6, because 2.5 gallons of 0 IBU water would need to be added to the 2.5 gallons of 31.2 IBU wort. Regardless of the IBU level of the wort in the boil kettle, when you add water to it, it is going to be diluted down. The Vb/Vr needs to be at the end of every string of IBU additions, if it is a 1:1 (full boil) ratio, nothing will change, anything less and it will drop the IBUs accordingly. IBUs are directly related to PPM, so inceasing the fluid into which they are disolved, will decrease the PPM.

**FlyGuy** · 12-04-2008, 07:21 AM

BarleyWater, you have the right idea here, but are missing the detail in Palmer's equations. His calculations are correct. You only need to know the recipe volume and the boil gravity to compute IBUs according to the Tinseth formula (provided that you do not exceed the theoretical maximum IBUs in the boil kettle).

Think of it this way, if you know your utilization (which depends on boil gravity, not boil volume) you can estimate the amount of alpha acids that will be isomerized in the boil kettle.

Once you know that total amount, it is easy to predict the concentration in the finished beer -- you just take that amount and divide by the total volume of the beer.

The ratio of the boil volume to the recipe volume isn't necessary in either of those steps. The only hiccup (not discussed by Palmer) is when you hit the wall in the boil kettle and saturate your wort with the maximum amount of isomerized AAs it can hold (probably around 100 IBUs, as you pointed out earlier). THEN the boil volume and dilution factor become important, because 100 IBUs in a small boil volume is going to mean a lower concentration of isomerized AAs in your final beer than 100 IBUs in a larger boil volume.

FWIW, you can always compute your IBUs for the boil, then factor in the dilution factor afterwards to scale up to the recipe volume. But your equation didn't do that because your calculation of IBU contributions from each hop addition was based on the recipe volume, not the boil volume. Just switch all those Vr's at the front of your equation to Vb's and it will work.

Cheers.

Quote:

Originally Posted by BarleyWater

This is my point right here, Plamer has a small but significant flaw in HIS equation. He states on that page...

He goes on to use this number, 1.080, to formulate the rest of the recipe using Tinseth's formula which is not intended for partial boil brews, and he does not take into account the wort being diluted by water after the boil, only the higher gravity of the boil. The sample he gave resulted in 31.2IBUs, but really should have been 15.6, because 2.5 gallons of 0 IBU water would need to be added to the 2.5 gallons of 31.2 IBU wort. Regardless of the IBU level of the wort in the boil kettle, when you add water to it, it is going to be diluted down. The Vb/Vr needs to be at the end of every string of IBU additions, if it is a 1:1 (full boil) ratio, nothing will change, anything less and it will drop the IBUs accordingly. IBUs are directly related to PPM, so inceasing the fluid into which they are disolved, will decrease the PPM.

12-03-2008, 05:23 PM	#13 (permalink)
FlyGuy Señor Member Recipes Join Date: Jan 2007 Location: Calgary, Alberta Posts: 2,882 FlyGuy's Gallery BLOG ENTRIES: 9	Also to the OP, no offense intended here, but what is different about your formula than the standard calculation of IBUs that people have used for a long time? One would normally compute the IBU contribution of each hop addition independently, based on the gravity of the wort anyways, and then add them up to get a total. Isn't that what you did here, or am I missing something? (Sorry if I am being thick.) __________________ Cheap 10 gal cooler MLT • $3 Autosiphon • Aluminum Pot FAQ • Easy Steam Injection Mash System • Make a Frozen Yeast Bank

12-03-2008, 09:13 PM	#15 (permalink)
FlyGuy Señor Member Recipes Join Date: Jan 2007 Location: Calgary, Alberta Posts: 2,882 FlyGuy's Gallery BLOG ENTRIES: 9	OK, I think I understand what you have done. You are trying to correct for the dilution effect on IBUs. I have some suggested improvements here. There is a small but significant flaw in your thinking -- the dilution effect is only relevant to the calculation of the theoretical MAXIMUM IBUs obtained in your boil. For recipes that don't exceed this maximum in the boil kettle, no dilution correction is necessary -- i.e. you don't need your formula, just use the conventional calculations. For example, look at the example Palmer provides in "How to Brew" he actually walks you through a partial boil. It is a 5 gal recipe with a 3 gal boil. He uses the method I mentioned in my previous post (i.e. figure out the utilization and resulting IBUs at each addition and sum them up for total IBUs in the batch). Hoppy beers: Now, let's consider a large hop addition where you might actually hit that maximum limit for isomerized alpha acids. In this situation, you should calculate the IBUs for the boil (not the recipe) first to check if you are exceeding the theoretical maximum IBUs. The computation is exactly the same as what Palmer describes, except that we will use the boil volume, not the recipe volume for this calculation: IBU = Sum[ (AAU * U * 74.89) / Vb ] If the result exceeds the theoretical maximum IBUs (e.g., 100), then bitterness of this recipe is going to be stunted by the dilution. To determine the resulting bitterness of the recipe, the following formula can be used: IBU = AAmax Vb* / Vr where AAmax is your theoretical limit to AA extraction (e.g., 100 IBU). Example: To illustrate using your example with two BIG hop additions and a 2.5 gal boil volume, here is what we get: boil IBU = Sum[ (AAU * U * 74.89) / Vb ] = [(260.23174.89/5)+(120.08474.89/5)] = 210 That exceeds the AAmax of 100 IBU, so the recipe is going to also be limited to the following bitterness: recipe IBU = AAmax * Vb / Vr = 100 * 2.5 / 5 = 50 I think this was what you were trying to achieve in your formula (note the common term Vb/Vr in both your and my equations). Hope that made sense. I'll try to write this up in a new post along with a quick spreadsheet to do the calculations given to clean up the presentation. Cheers! __________________ Cheap 10 gal cooler MLT • $3 Autosiphon • Aluminum Pot FAQ • Easy Steam Injection Mash System • Make a Frozen Yeast Bank

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12-03-2008, 04:59 PM	#11 (permalink)
jkarp Senior Member Recipes Join Date: Jun 2008 Location: Elizabeth, CO Posts: 120	A lot of nice work, but it still flies in the face of the results from the 2007 International Brewers Symposium. There's a LOT more variables to IBU production than wort volume. Sure would be nice if a simple test for calculating isomerized AA in finished beer were available so we could validate. Hell even the Tinseth table could use a proper vetting IMO.

12-03-2008, 10:17 PM	#18 (permalink)
jkarp Senior Member Recipes Join Date: Jun 2008 Location: Elizabeth, CO Posts: 120	No criticism was made nor implied FlyGuy. As far as being constructive, the information from the Brewers Symposium, along with links to John Palmer's report on it has been discussed in several different threads here over recent months. I'm sorry you missed them, but it should be an easy search. There was nothing in my OP that was un-supportive. I simply lamented the fact that we don't have a simple IBU test as it would make fine-tuning IBU calculations (the original goal of this thread) much easier and allow the numerous complicating factors BarleyWater pointed out to be tested and taken into account.