I believe I read that IBU’s can rise when you use more than x amount of water in an extract boil. How is this?
The theory is that higher gravity wort will have a lower level of hop utilazation.
So the thinner the wort the more bitterness one would get from the same amount of hops.
John Palmer has a nice table (Table 7) that shows hop utilization percentage as a function of boil time and wort gravity: http://www.howtobrew.com/section1/chapter5-5.html
Pick a boil time, say 60 minutes. You get about 28% utilization from your hops if boiling in a 1.030 solution whereas you only get about 18% if you were boiling in a 1.080 solution. This isn’t all that big a deal for people who do full-boils, but if you’re doing partial boils using extract, this could become an effect you’d want to compensate for (in this example, you’d want to increase your 60-minute hops by about 50%).
The other thing to keep in mind is that the solubility limit for alpha acids is around 100 IBU. So if you’re doing a 3 gal boil and diluting to 5.5 gal, for example, you can never exceed 100*3/5.5 = 55 IBU, give or take. If you’ve developed a recipe that takes advantage of that without realizing it, switching it to a less dilute concentrated boil could result in increased bitterness.
fixed that for you. but the concept is there. if you dilute less post boil you will get better hop utilization
Yeah, that. I’ve had coffee now. :
This is one of the reasons extract brewers tend to add a majority of the extract with 5 or so minutes left in the boil to get a better hop utilization.
I’ve never done that, what am I missing?