I recently made a pale ale and decided after flameout and chilling that I wanted to add some orange zest. I waited until I racked the beer to the bright tank (secondary). Before I racked, I zested three oranges. Basically, I used a sterilized potato peeler and was very meticulous not to get any of the white pith with the zest peels. I suppose you could grate the zest, but I wanted to avoid the particles and go with larger peels.
After getting the zest, I put them in a small sterlized pot with about 2 oz vodka and just enough water to cover. I brought this to boil and let it go for about 2-3 minutes. Then I put the whole solution (peels and all) into the bright tank and siphoned the beer on top of the solution. Before placing the airlock on, I gave the beer gentle stir to circulate the orange zest solution.
After two days, the orange flavor was very slight. For me, I didn't want an overpowering flavor so I'm happy with the direction. I expect more orange flavor to emerge over the next week or two. If it gets two much, I will rack the beer off the peels. I'll try to post an update later...
QUOTE=smizak;1784061]The key is to only zest the very outside of the rind, just the colored part, and avoid zesting any of the white pith underneath. As long as you do that, you shouldn't pick up any bitterness from the zest.[/QUOTE]