whitmorr86
Member
Can anyone shed some light on the differences between adding prior to boil vs mid-boil or flameout? I understand it can change color but I'm wondering if there are any effects on body or flavor.
It can also affect how many IBUs you get out of your hops. A lower gravity boil, even for a bit, means the hops will contribute more IBUs.
Question: We have been trained through reading literature of all kinds that alpha acid isomerization is affected by wort gravity?
John Palmer: Yeah we have haven't we. Yeah, and like I said this seminar, this conference was a real eye opener for me. Made me realize that I had been, you know, following the same assumptions as everyone else for a long time. But, yeah, it turns out that isomerization kinetics--that is the rate at which alpha acid will isomerize into isoalpha and become soluble--that's pretty constant. The amount of wort gravity really doesn't affect that, you know hardly at all.
John Palmer: I think the spirit of the advice is still sound. I think maybe the magnitude of the advice is reduced because if you go into the fact that extract has already been boiled once and a lot of the hot break material has already come out--now, hot break coagulation or precipitation in the boil is a function of the total amount of protein present and the temperature you reach during the boil (which really doesn't change very much, it shifts maybe a half a degree because we're not talking really high gravities when we brew even when you do a concentrated boil like 1.100 the boiling point doesn't change appreciably, maybe it'll go up to 100.5C or 101, but I mean it's small).
So there's a solubility limit of protein at boiling point, and, so you've got a supersaturated solution, hot break comes out, when you take that extract and you do a normal gravity boil, say a 1.040 boil, well most of that protein has already come out. You're not going to get much hot break in a 1.040 boil. You're probably giong to get less alpha taken out of solution then. If you do a concentrated boil, this 1.100 that we're talking about when you put all this extract in the pot and boil it for an hour, you get a lot of hot break then because you've gotten a higher concentration of protein that's going to precipitate out. And that's going to carry off a percentage of the isoalpha.
But kind of the unknown here is, is the amount of hot break from a concentrated malt extract boil of 1.100, is that the same amount of hot break you would get from an all-grain mash boil of 1.100--probably not.
it doesn't reach any cut-and-dry guidelines for home brewers, but gives you a lot of stuff to consider when thinking about hop utilization in different kinds of beers.
it doesn't reach any cut-and-dry guidelines for home brewers, but gives you a lot of stuff to consider when thinking about hop utilization in different kinds of beers.
So the entire discussion is pointless for most casual brewers then. If these very technical discussions don't result in applications then what is the point?
I think Jamil Z and John Palmer's recommendation to keep boil gravity the same as recipe gravity is still the most sound advice I've read/heard regarding extract addition.
It doesn't make sense that just keeping the boil gravity the same as the final gravity will keep the hop utilization the same.
If you're doing a 2.5 gallon boil for a 5 gallon batch you're putting in the full amount of hops in half as much water. Won't you reach a point where the acid from the hops won't dissolve as readily due to the high concentration of hop acid in the wort?
I'll have to re-read the section in Brewing Classic Styles that discusses this, but from memory I believe they state the volume of liquid in a partial boil is more than enough to utilize hops to their fullest.
[I]Brewing Classic Styles[/I] pages 30 & 31. said:These alpha acids will be isomerized based on the boiling time and wort gravity. The physical size of the boiling pot doesn't really affect the utilization like the boil gravity does, because the amount of alpha acid dissolved into the wort is still relatively small compared to the total volume.
I just used the 'Search inside this book' feature at Amazon and found the following:
These alpha acids will be isomerized based on the boiling time and wort gravity. The physical size of the boiling pot doesn't really affect the utilization like the boil gravity does, because the amount of alpha acid dissolved into the wort is still relatively small compared to the total volume.
Good to know.
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