Hop Utilization

So, utilization goes up the longer you boil...blah, blah. Does anyone know where the point is at which it stops? The point at which there is just no more utilization. I see Palmer's chart/nomograph going up to 30% utilization at the max. Is this really the maximum utilization possible or is it just that there is no reason to go any higher because of some adverse effects or something, or once you get that high you've been boiling for half an ice age and your starting to mummify?

Probably your latter reason. I'm looking through Daniels' Designing Great Beers and he gives a figure for the hop utilization curve (Figure 9.4 in his book). He doesn't say from where the information came, perhaps M. Garetz, Using Hops: The Complete Guide to Hops for the Craft Brewer, and I don't know how faithfully the curve was reproduced in Daniels' work.

The slope of the curve begins to flatten off as you get to higher boil times, but it doesn't seem to be getting entirely flat. I'm an engineer and a nerd , so I tried a regression fit of the curve and got a pretty good match. The equation has no asymptotes if you extrapolate past the data (120 minutes). The graph also shows 100% utilization after 260 minutes, but again, the data set doesn't go that high so the number probably isn't reliable.

So in theory, it seems the utilization level continues to go up with increased boil times. But in practice, who's going to sit there that long!?!

BTW, this graph shows utlizations up into the 40% range at 90-120 minutes.

Effective max is 60 min. From 60min to 90, you MIGHT get another 1% utilization, but that depends on about 30 factors, including moon phase and whether you add them with your left hand or right

For the numbers, a 1.040 beer will get something like 0.252/IBU utilization @ 60, 0.270 @90. Again, this is just on paper.

From the Hop FAQ

One question that appears on occasion is whether you lose bitterness if you boil the hops for too long, e.g. longer than two hours. According to Glenn Tinseth, multiple studies have shown that alpha acid utilization always increases with boil time, even out to 3 hours of boiling. The reason the tables quit around 60 minutes of boiling, is that little utilization is gained beyond that. In fact, after about 45 minutes the curve becomes quite flat. In other words, beyond that the utilization increase is small compared to the added time involved. It is speculated that commercial brewers found that beyond 45-60 minutes or so, the benefit of the added utilization was more than offset by the cost of the energy to continue the boil as well as the cost of the added time in the process.

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If you look through Tinseth's equation, you'll notice that the utilization is proportional to (1-e^-0.04*t). As t gets bigger, this factor approaches 1.

time / time
(min) factor
-------------
1 4%
30 70%
60 91%
75 95%
90 97%
120 99%

So it never really 'stops' but you're just not getting that much more out of your hops. Boiling an ounce of hops for 2 hours instead of 1 would save what? 1/10th of an ounce or so?

goatchze said:

...in theory, it seems the utilization level continues to go up with increased boil times...

Click to expand...

I tend to look at it as the boil time increases the volume decreases giving it the appearance of more bitterness... j/k

I, too, use the 60 min max method.

Yeah, there really is a limit. 60 minutes is a compromise between conversion and energy usage.

david_42,
I know it has been a while since you posted the above figure (Fig. 7), but can you supply the reference information for it (title of paper, authors, journal volume, year, and page number)? TIA