IBU Values and Partial Boils

[Super64]

I just read on line that if you do a partial boil, say 2.5 gallons for a 5 gallon batch, that you need to build your recipe with twice the IBU values to compensate for the fact that you will be adding 2.5 gallons of top off water to the primary.

Can anyone confirm this?

I've been brewing small batches starting with 2.5 gallon boils that can end up with 1.75 gallons of wort. That would mean I'd need to adjust my hop value up by about 42%.

 

[Yooper]

No, that's not so. You might need 15-25% more hops to get the same bittering, but even that is debatable.

One thing you can do easily is add the bulk of the extract at the end of the boil. That way your wort doesn't darken and get carmelized-tasting and the hops utilization will improve as well.

 

[hardmike]

One thing you can do easily is add the bulk of the extract at the end of the boil. That way your wort doesn't darken and get carmelized-tasting and the hops utilization will improve as well.

have you ever done that? i did it with my last to beers. it really sucks. the extract do not want to dissolve plus it get hit with so much steam on its way into the pot it basically falls in chunks!
besides that it is impossible to claculate the change in utilization for the last 10 minutes of the boil at full gravity. So it really just gets more confusing.
Do you have a smart phone? find an app that claculates hop bitterness and SG and everything. find your boil gravity and calculate what your utilization is gonna be.
The problem is that with a partial boil, the gravity is much higher and you wont get as much bitterness from your hops.
If you are building a recipe...try using the beer recipator. I know it asks for the boil volume so i think it might calculate all that stuff for you.

 

[Redpiper]

An easy way I've found to add the late extract is to use a second pot. I heat up a gallon or so of water in one of my wife's cooking pots when I start my boil. Once the main boil is going, I mix the extra extract into the hot water. 30 minutes later it is well dissolved.

Then I bring this to just under a boil and ladle it into the main boil in the last 10 minutes. You do have to leave a little space in the main pot (evaporation makes more) but this hasn't been a problem.

 

[Super64]

I typically do late adds and use DME. I put a couple of pounds in at the start of the boil along with the bittering hops, then add the balance of the extract at the 15 minute mark.

I have also found a hot water slurry makes the addition a little easier.

 

[ayoungrad]

When I use DME I add all of it at flameout. I use a large wisk and with the wisk I have no issues with dissolving it - even up to 5 pounds at flameout (IIPA).

In re: utilization and partial boils. I think the OP is partially correct about the dilution factor IF the OP is talking about 100+IBU. I have never found a definitive answer to this but here is the best I can come up with...

It seems to be agreed upon that there is a maximum taste threshold for bitterness - around 100 IBU. However, some seem to also think there is a maximum IBU threshold that can dissolve/form in the wort. So, if, for example, you get 100IBU in your wort in the boil, when you dilute it in half, you will get 1/2 the IBU - so the maximum is 50 with a 50:50 dilution.

I'm not saying this is true with definity but it seems at least close to the mark based on my experiences with dilution and IBU. I now do full boils (I even have to do two boils for each batch to achieve this with my set-up) and I really, really love the results.

Just another thought. There are also those who debate the truth of wort concentration affecting IBU utilization. Some feel utilization is related to other factors including, from what I understand, break formation. I do not know exactly all of the factors that they say contribute, but I use Tinseth which uses concentration as a major factor and I find it to be fairly accurate.

 

[jkarp]

The problem is that with a partial boil, the gravity is much higher and you wont get as much bitterness from your hops.

Nope. Gravity has no direct impact on hop utilization. This myth was debunked years ago.

 

[ayoungrad]

One other thought - I just read my post. If the idea of dilution is real, it is probably true for small beers too. The only issue is that you really can't do a big IBU beer at all. Again, not sure how accurate this is, but full boils made a big difference in the bitterness of my beers.

 

[jkarp]

BBR/BYO did an experiment on extract partial/full boils and sent the results to be lab tested for IBUs. No difference was found. Recipe was an IPA too.

 

[ayoungrad]

BBR/BYO did an experiment on extract partial/full boils and sent the results to be lab tested for IBUs. No difference was found. Recipe was an IPA too.

Interesting. I guess its one of those things where I must have also changed something else along the line that made the true difference.

 

[Yooper]

have you ever done that? i did it with my last to beers. it really sucks. the extract do not want to dissolve plus it get hit with so much steam on its way into the pot it basically falls in chunks!
besides that it is impossible to claculate the change in utilization for the last 10 minutes of the boil at full gravity. So it really just gets more confusing.
Do you have a smart phone? find an app that claculates hop bitterness and SG and everything. find your boil gravity and calculate what your utilization is gonna be.
The problem is that with a partial boil, the gravity is much higher and you wont get as much bitterness from your hops.
If you are building a recipe...try using the beer recipator. I know it asks for the boil volume so i think it might calculate all that stuff for you.

Sure, I've done it lots of times. I use a whisk and whisk it in. It's fine. It's not any worse than making gravy and adding flour to water!

The IBU changes don't matter a bit. It's not the gravity of the wort which changes IBUs, it's the amount of break material. So, you actually get MORE bittering out of adding the extract late but it's not a large difference.

The first time I did it was with a lower IBU beer, about 15 IBUs. And yes, the beer did have more bittering in it, at least at first. This was years ago, before anybody talked about adding extract at the end of the boil. The bittering mellowed out in a few weeks, though, and it was a better beer because of the late addition of the extract. In a higher IBU beer, I haven't noticed a difference in the bittering, but it's a better beer with less extract-y taste.

Keep in mind that a late extract addition would keep the wort more like an AG batch, or a full boil of extract, in a partial boil. A condensed wort is like condensed soup- adding water to get to the "real" product. Adding the extract later in the boil, or even at the end, keeps the wort from overthickening and darkening.

 

[HollywoodMX]

I find that the steeping grains taste penetration is also effected by the lack of the full boil.

 

[Super64]

Well here's something interesting....

I am making an IIPA, and using QBrew and The Beer Recipator to calculate the values.

Recipe
Small batch (3 gallons, 2.5 gallon boil)
Crystal 60L Steeped
3lbs Amber DME
2lbs Extra Light DME
1oz Chinook hops @ 60min
.5 oz Cascade hops @ 30min
.5 oz Cascade hops @ 15min

______QBrew______Recipator
O.G. =1.078_______1.077
F.G. =1.019_______1.018
SRM =13__________19
ABV =7.5%________7.6%
IBU =86________68 <---- What? Who do I believe?

 

[jkarp]

IBU =86________68 <---- What? Who do I believe?

Are they set to use the same IBU formula?

 

[Super64]

Thanks, Karp,

If you hadn't mentioned that, I would not have know I could select the Tinseth formula in QBrew.

A little research around the .Net shows that Tastey Brew's IBU calculator come up with 59.5 IBUs. RoofTop Brew comes up with 68 Ibs, Qbrew now shows 69 IBUs.
All using the Tinseth formula. Some ask for batch/boil size too.

 

[BobsOwnBrew68]

I too had problems with adding extracts at the end of the boil. Not only did it tend to lower the boil temp, but I also found the beer was cloudier than normal.

Has anyone tried boiling the hops separate from the wort? I've started doing this and have found the hop bitterness and flavor much crisper....anecdotal evidence there is hop utilization loss in partial batch boils.

I boil the hops in water in a saucepan (1-2 qts) and the extracts in a canning pot as usual. While the hops are boiling, I raise the temp of the pot and prep the extracts.....which means the extracts boil about half an hour. When the hops are finished (1 hr), I add them to the wort in the canning pot.

Not only is the hop utilization more complete, but the total boil time is reduced because there is less time waiting for water to boil.

 

[jkarp]

A little research around the .Net shows that Tastey Brew's IBU calculator come up with 59.5 IBUs. RoofTop Brew comes up with 68 Ibs, Qbrew now shows 69 IBUs.

The last variable of course is what AA% are each tool using for the selected hops. You should be adjusting them for the actual AA of yours as they vary from year to year.

 

[Super64]

I was, actually. They all had the Chinook AA% at 12%, the package I have says 11.5%
The Cascade was averaged at 6.60%, mine said 6.0%.

I'm glad I found this out before I brewed my almost non-IPA