I'm hoping I can get JMF or the other hard-core infusers around here to give me some ideas.
A while back, I started tinkering with making bitters, and my favorite at the time was a riff on Jeffrey Morgenthaler's grapefruit bitters recipe. It was fantastic, and everybody I shared the stuff with loved it. Of course, a liter of bitters goes a LONG way, so two years later, I still have quite a bit. It still tastes nice, but has lost a lot of the fresh, aromatic grapefruitiness.
This year, I have been going a little nuts on the extraction front - I have made a pile of extracts and am enjoying mixing them up in various concoctions to make all sorts of bitters, and some of the leftovers will be turned into liqueurs when I have all of my bitters figured out.
Is there a way for me to keep the volatiles in the extract/liqueur/bitters longer? Commercial brands seem to be able to make products with a much longer shelf life. Glycerin? More sugar? Anything?