backing off bittering hops when doing full wort boil

[Zokfend]

I've been doing LME/grains recipes from High Gravity for the past several months now. One thing I've noticed is that their recipes always say that if you want to do a full wort boil of 6 gallons instead of partial wort boil of 3 gallons, you should back off the amount of bittering hops by 20%.

To me it seems backwards, but whatever. I'll just follow directions, right?

So now I am getting ready to do another recipe of theirs, their Maison de Ferme, and this particular recipe doesn't give instructions what to do if you decide to do a full wort boil of 6 gallons. It just says to do 3 gallon wort boil. So I called High Gravity and asked them if I needed to back off the bittering hops by 20% if I decide to do a full 6 gallon wort boil. The guy tells me that backing off hops really only applies to all-grain, and that backing off hops is not necessary for any of their extract recipes.

So now I'm totally confused, because prior to this upcoming batch, my previous three batches were all full-wort boils where I followed instructions and backed off the bittering hops by 20%, and the end-result was in my opinion right where it needed to be (bitter-wise). Had I done a partial wort boil, I can only guess my two previous batches would have been overly bitter?

Comments?

 

[BradleyBrew]

From my knowledge you back off your hop addition by 20% because you will get far greater hop utilization with increased water volume.

If you would have decreased your hop addition by 20% during partial boils then your IBU's would have been lower and the exact opposite would have happened the beer would have been under bittered not over because hop utilization in partial boil is less. Hope that helps!

Try www.beercalculus.com. You can enter the exact AA for each style of hop you are using, the lenght of time, boil volume, and batch volume. I have used it and its really close for being FREE software!

 

[Daybis]

I wouldn't stress about it too much. You will get better hop utilization with a larger boil, but I wouldn't worry about it honestly. I've also never heard of all-grain effecting hop utilization differently than extract. I would brew the beer with all of the ingredients that came with the kit. If you find the beer to be too hoppy or bitter for you liking, you can back off the hops a little bit the next time you brew it.

 

[C2H6O]

I am curious about this as well since I recently switched to full boil volumes. I use Beersmith for my recipe calculations. When I select my brew equipment it sets my starting boil volume as 6gal. - is it calculating the hop utilization and resulting IBU based on that volume or is a manual conversion (reduction) also required? The last 2 batches I have made were slightly more bitter than I was expecting and I am wondering if this is the culprit.

 

[Yooper]

I am curious about this as well since I recently switched to full boil volumes. I use Beersmith for my recipe calculations. When I select my brew equipment it sets my starting boil volume as 6gal. - is it calculating the hop utilization and resulting IBU based on that volume or is a manual conversion (reduction) also required? The last 2 batches I have made were slightly more bitter than I was expecting and I am wondering if this is the culprit.

This is one of the "newest" thoughts now in brewing. It was universally assumed a while back that a full boil increased your hops utilization due to the lowered gravity of a full boil. In fact, in Palmer's first book he describes just that- a higher gravity wort causing lowered hops utilization (like in a partial boil).

But then, about three years ago, he came out and said he was wrong about that! That there is some differences in utilization but not due to the gravity of the boil, but instead break material, and not to adjust the IBUs when you calculate it.

Now, here is my own non-scientific discovery! When I did a full boil the first time on my Dead Guy clone recipe (and later a late-extract addition which simulates the same thing), I remember tasting it and saying "Wow- this beer is twice as bitter as last time!" I later bought Beersmith and played with it. Sure enough, the IBUs went from 15 to 27! HOWEVER, that stronger bitterness mellowed and within a few weeks it was indistinguishable from the "original".

Another thing I discovered was that going from 15 to 27 IBUs in a lower IBU beer is HUGE, compared to doing something like a pale ale and going from 35 to 40 IBUs, which is barely discernible (even if there WERE changes)

Basic Brewing Radio did an experiment last year where they had brewers make an extract batch with a partial boil and one with a full boil and one with late extract addition with no recipe changes. There were not different, and had the same IBUs.

I guess what this all has taught me is that we used to think that IBUs were greatly affected by the gravity/composition of the boil. Now we are learning it is not.

The main difference in lowered IBUs in partial boils has to do with dilution. The "most" IBUs you can get into solution in a boil is about 100 total. The oils just can't isomerize anymore. So, if you're boiling 2.5 gallons and topping up with 2.5 gallons, you just can't make a beer with more than 50 IBUs no matter how many hops you add. (100 IBUs (2.5 gallons) + 0 IBUs (top up water)= 50 IBUs. That's the limiting factor, and why some extract batches can taste sweeter than planned.

So, in other words, I'd say that doing a full boil is great. And if you can't do a full boil, add the extract late in the boil to help minimize maillard reactions and that "carmelly" taste you can get from extract. But don't worry about the hops! A good way to hop it would be just to hop it as if you were making the AG version of the beer if you're making your own recipe, or simply follow the directions on a purchased kit. But for a hoppy/bitter beer, for best results boil the most water you can.

 

[C2H6O]

Yooper - as always thanks for the detailed and informed response. Now that you mention it I was basing that off of samples I was tasting while taking my OG readings. I will have to reevaluate them as they condition. I also have to say your dead guy recipe is great as I am drinking that now!!

 

[Zokfend]

Yooper sounds like a chemist or some kind of scientist. Way over my head, talking about oils not being able to isomerize. I wonder if I can use those fifty dollar phrases to my wife, and she'd be impressed.

 

[Yooper]

Yooper sounds like a chemist or some kind of scientist. Way over my head, talking about oils not being able to isomerize. I wonder if I can use those fifty dollar phrases to my wife, and she'd be impressed.

Oh, no. NOT me! I'm am the furtherest thing from a chemist! I have just the most rudimentary understanding of all of the brewing basics. Trust me, I'm sort of a dummy about the science aspect of all this!

The thing about the oils isomerizing is actually not that tough, though. The basic idea is that the hops contain aromatic resins. These are not soluble in water, and must be extracted by boiling (isomerized). The longer it's boiled, the greater the percentage of isomerization and thus more bittering. That's why bittering hops are typically boiled for 60 minutes (as the percentage of isomerization isn't appreciably greater after longer than 60 minutes) while flavor and aroma hops (which you want the aromatics from, not so much to isomerize those bittering compounds) are boiled for much less time.

But saying things like "isomerize" probably made me sound smart!