Hop Utilization Question

[Lordsoth]

Unfortunately, for the time being, I am stuck doing partial mashes with a partial boil on my stove top. I've been reading a lot about hop utilization and partial boils, and I realize that I will need to compensate for some loss of hop utilization for my upcoming IPA.

Basically, I am able to boil 4.5 gallons right now, and in my previous beers, what I have done is continuously feed water that I have heated in a smaller pan into the brewpot, to keep the water level pretty much constantly at 4-4.5 gallons throughout the entire 60 minute boil, so I only need to top off with 1-1.5 gallons at the end. That said, my past beers were a hefe, a dunkel, a scottish ale and other beers without a strong hop profile, so utilization wasn't as big of a factor (and those beers turned out great btw).

My question to you all is, given my current process of adding water to the boil, what effect might this have on my hop utilization? I realize I will still need to account for the 1.5 gallons of top off water and DME addition, but what about my boiling practice? Might this negatively (or positively) impact utilization in some way?

 

[BargainFittings]

I don't think the addition is going to change your utilization enough to worry about it. You are basically keeping the volume dilution the same through the boil.

I would set the software for a partial boil at the volume you start with and leave it at that.

 

[david_42]

Adding water slowly will not change the utilization.

You can also pre-boil some of the hops in your top-off water.

 

[Lordsoth]

Cool, thanks for the help guys! I didn't think it would be an issue, but I'm really trying to brew a decent IPA and want to cover all my bases.

 

[kanzimonson]

I wrote a program in excel for my hop utilization using the Rager formula. One of the things I like about the Rager formula is that you can punch in the gravity of the boil and the formula takes into account lower utilization due to higher gravity worts. However, in the case of hops that are boiled for a long time, I'm never sure what to put for this number.

What I've ended up doing is just put the gravity of the wort at the moment the hops are put into the boil. I figure the majority of bitterness is extracted earlier in the boil, so this is the best number I can use. I use some basic math to figure out the gravity of the boil at any moment by assuming my boil-off rate, total volume, etc.

Furthermore, I use this same formula every time, so with every brew I become more familiar with my system. In your case, since you're maintaining nearly the same volume, you would definitely get a little better utilization. My recommendation is to just do it the same every time. Maybe you could even deliberately time your additions of new hot water to the boil. Every 15 minutes you add X amount? Might be a lot of work, though.

 

[Yooper]

Don't forget that you can add the majority of the extract at flame out, to really improve hops utilization and keep the color of the beer lighter, which is great for IPAs.

If you have some brewing software, some of the programs have a "late addition" option to figure the IBUs. Or, if you don't you could post a recipe here and we could run it through Beersmith for you.

 

[Lordsoth]

Wow, some great information here, I think I feel confident going forward now. I do presently use Beersmith, and according to it, the difference between adding DME at the start of the boil and with a 15 min addition, is about 18 IBUs and adding the DME at flame out (or 1 minute) gives me an additional 5 IBUs.

With my previous beers I have added half my DME at the start of the boil and the other half at 15 mins. Is there any reason I couldn't add it all at 15 mins., or as Yooper recommended at flame-out?