3 beer recipe calculators. 3 very different results. - Page 2

**Yooper** · 01-21-2012, 03:01 AM

Quote:

Originally Posted by cshamilton

For hop alpha acids there is a limit to how much can be dissolved in water (it works out to be about 100 IBUs in bitterness). So if you have a lot of bittering hops in 2.5 gallons and get to 100 IBUs, then dilute to 5 gallons you end up with 50 IBUs. If you do a full boil more alpha acids dissolve so the same recipe could be 100 IBUs if you had enough bittering hops.

Yep, that's the jist of it. Lately, new thinking has said that wort gravity has very little impact on the hops utilization. But it's been said all along (and still today) that there is a theoretical maximum of hops oils that can isomerize, generally 100 IBUs.

If you make 5 gallons of 100 IBU wort, then you will have a 100 IBU beer. But if you make 2.5 gallons of 100 IBU wort and top off with 2.5 gallons of 0 IBU wort (water), you get a maximum of 50 IBUs in the beer. Not due to the lack of hops, but instead that the wort can only "hold" so much hops oils in solution and they don't isomerize above about 100 IBUs.

That's why it's so tough to make a great IPA with a partial boil. It's just not possible to get more than about 50-70 IBUs in a partial boil.

jeremydgreat · 01-21-2012, 03:27 AM

Wow. I just learned a lot about hops. Thank you. I swear, if chemistry had been taught to me like this in college, maybe I would have cared more.

Wikipedia: Isomerisation - Better beer through science. haha.

What you're explaining sounded unbelievable (or at least unintuitive at first) at first, but makes total sense now.

**lawle102** · 01-22-2012, 01:12 PM

Jeremy, I'm in the same boat as you. I want to make an IPA with a high ibu but apparently it's just not too feasible with partial boil set up. Looks like I need a bigger kettle.