Just as RCope has done. I've used several. Keep in mind that I'm lazy so I just use the whole quart in a 5 gallon batch of beer or mead. That being said, I did make a SkeeterPee mead and I only used the recommended amount of Coloma Lemon concentrate to match the recipe. It was great and I got to make a second batch of mead with the leftover concentrate.
I had a quart of plum concentrate for the longest time and finally made a mead with it. while I found it underwhelming when it was fermenting and aging, once I kegged it and started drinking it, it's great. I will be making a plum beer of some sort with the same concentrate in the future, dosed at 1 quart of concentrate for a 5 gallon batch of beer.
Dig around a bit for recommendations of "pounds of fruit per gallon" for peaches, then try to find a reference for "quarts of juice per pound" and do the math, if you'd like to. That's the tough way.
Peach is a very subtle flavor. To get real peach flavor in a beer / mead / wine, apricot works best. I would encourage you to put one quart of peach concentrate into your IPA and see how it goes. If it's not to your liking, try again. You can always ship me samples for tasting and "consultation fee". More than just samples if you don't like it.
Now that I think of it, I think I've got a Pro-Am out there with Coloma pear concentrate added. It just happened to work out that the dose used in my homebrew scaled up to one of their 1.5 gallon concentrates for the brewery's batch size.
homebrudoc
