Whirlpool IBU Calcs

[home_brew]

Thankful that brewing software is now able to consider IBU's from the whirlpool.  It wasn't that long ago that this wasn't factored in.  But are the whirlpool hop calcs correct in Beersmith?

We know that the whirlpool only isomerizes the AA while it's hot enough - 170F+ I think it is.  There will also be carry-over IBUs from the boil hops because they extend their boil time by a factor of the time that the wort remains above 170F as with the ones added in the whirlpool, just on a diminishing curve once we reach flameout.

Why, when i add an oz of hops at the last 5 min of the boil, does it give me less IBU than when I add the same oz for a 15min whirlpool? 

I would expect that given the equipment profile, and liquid volume, and ambient temp of the surrounding air, it should be possible to factor in the thermal retention of my kettle so that the IBU's could be more accurately calc'd with the whirlpool properly factored in. 

Or is this a tall order?

[brewfun]

But are the whirlpool hop calcs correct in Beersmith?

As close as there is any data, yes.    BeerSmith uses available and accepted formulas for all of its' predictions. At this time, it uses the "similar contribution to a 20 min addition" consensus that developed in 2011. 

The fact is that hop bittering research all seems to stop at 50 IBU and there really isn't any research data available above 50 IBU. What does exist (from University of Oregon) shows it's more complex than simple IBUs. There's saturation, perception and texture to consider, as well. What their research reveals is unhopped beer still measures up to 4 IBU and that pure IBU bitterness can't be detected above the 60 to 65 IBU range. I think they presented their findings in 2013.

Why, when i add an oz of hops at the last 5 min of the boil, does it give me less IBU than when I add the same oz for a 15min whirlpool?

Totally different issue than the above.

At this time, BeerSmith calculates WP separately from the boil because the available boil isomerization calculations don't directly cover WP, except basically an extension of the boil.

The thing is; the accuracy you're asking for is useful if you're adding a lot of WP hop to standard (<45 IBU) styles. If you're concerned about a few extra IBUs in a hoppy style, then it's probably near the 100 IBU saturation point and becomes more about saturating flavor.

I would expect that given the equipment profile, and liquid volume, and ambient temp of the surrounding air, it should be possible to factor in the thermal retention of my kettle so that the IBU's could be more accurately calc'd with the whirlpool properly factored in. 

Or, you can just use a thermometer.

For the last two years, there have been some interesting studies about hop flavor and new methods to calculate the actual bitterness properties of highly hopped beers.

[home_brew]

I'm okay with the calculated ibu from the boil, without a WP. I'm also okay with the ibu calculated in the WP. I'm just having trouble with the fact that Beersmith doesn't factor in any effect on the ibu calcs during the boil when a WP is added to the brew.

Check out this screenshot example in the attachment.

With no whirlpool, my 30min hop addition adds 15ibu. Now, if I add a 15min whirlpool with .01oz of hop which won't add any significant bittering whatsoever, Beersmith tells me I still get 15ibu in spite of increasing the effective boil time of the 30min addition to 60 min by adding a WP.  This should give me about 20ibu, not 15ibu shouldn't it?

To me, the WP time should also affect the calculated ibu for the boil hops directly proportional to the time that it spends above 170F. Unless I'm adding a ton of WP hops, I'm not concerned as much about the bitterness derived from the WP as I am about the time extension effect of the WP on the boil hops, especially in the steepest part of the isomerization curve when brewing, say, a hop-bursted IPA.

I know that perceived bitterness comes from roasted malt and from some types of yeast character and even from other hop qualities. We can't mathematically predict this and have to rely upon our tastebuds and experience in coping with this. But assuming that all other things are equal, what don't I understand about the way Beersmith appears not to calculate the boil ibu correctly when adding a WP? 

But then again, I swear that the dress is white with gold trim. ;O)

[Oginme]

What you describe is very process dependent and I am not sure anyone has done any measurements or modeling around the effect of whirlpool time on boil added hops.  For someone who does no-chill the answer would be very different from someone who starts chilling immediately following 20 minutes of whirlpooling/steeping of post boil hop additions. 

Then again, the whole calculation of IBU from hop adds anywhere in the system is really only valid for the system and process it was developed on.  Unless you are willing to invest in a number of actual IBU tests on your output, the calculation is at best an approximation anyway.  Most people's systems are probably withing +/- 5 IBU of the calculations, which as Brewfun pointed out only really affects those recipes <40 or 50 IBU.

My recommendation is to brew a clone of some beer you can readily obtain and know the brewer's values for IBU (and the model used to obtain it).  Do a taste test and determine if you are high or low compared to the commercial standard.  You can adjust you hop utilization and whirlpool utilization to suit what your taste buds tell you.

[brewfun]

what don't I understand about the way Beersmith appears not to calculate the boil ibu correctly when adding a WP? 

But then again, I swear that the dress is white with gold trim. ;O)

Hmmm. Alright. I hear what you're saying and I'm not arguing the logic of it. Empirically, it seems like the rise in IBUs should continue to follow the same curve as long as the wort is hot, correct?

If that empirical assumption is correct, then it should show up in real world examples, right? In other words, if I measure my IBUs in a lab, they will either confirm or challenge BeerSmith's model.

BeerSmith doesn't create its own formulas. It integrates accepted formulas and the most widely used is Tinseth. In the Tinseth model, about half of your utilization comes in the first 15 minutes, but that utilization is cut by about half for the next 15 minutes. So, as a single hop contribution, it would seem that you're correct in assuming the calculation is short by about 5 IBUs.

So, how does that play out according to real world lab measurements?

I brew commercially. The rig that provided the following data is 15 bbl steam fired. The boil time is 90 minutes, the minimum WP is 20 min, the stand time is 30 min and the chill is 40 min. So, a kettle hop charge is potentially amplified by an additional 90 minutes.

In these two examples, I extended the calculated time to the total contact time in hot wort. The wort was never below 190F.

Example 1: Dortmund Lager, OG 1.045, Recipe IBU 22. There's a charge at 20 min and at WP. Extended contact time is 26 IBU for an 18% increase. Lab result was 21.7 IBU.

Example 2: Red Ale, OG 1.065, Recipe IBU 36. There's about 17 IBU in the bittering charge. The rest is 10 min and WP. Extended contact time is 48 IBU (the bittering only rises by 2) for a 33% rise. Lab results were 35 to 37.

What this says to me is that BeerSmith gets this pretty correct. Before the addition of WP calcs, I had the hop utilization at 110%. It's at 100% with the WP calculation in place. So, my IBU model is the same as yours.

I know that with WP hops the initial bitterness is more intense, but as fermentation goes on it diminishes significantly. If I had the same wort balance with a 60 minute addition, I know the resulting beer would be over-bittered. I attribute some of this to hop tannins that precipitate and perhaps that the resulting isomers aren't as "sturdy" as they might be if fully boiled.

In the next few months, I'll be moving up to the largest system I've ever brewed on and that may change my recipe design. At the same time, I'll get to review some new research on the subject of >50 IBU hop effects. Hopefully, there will be surprises for me from both!

[home_brew]

Thank you. I appreciate the thorough response. I will be looking closer at Stone's methods as well. They tend to max out the kettle hops in a 90 min boil and add the rest in the post-boil.  I like the mental closure I'd get from that.