I bottled out the 2008 Grenache, and have tasted a significant evolution in the flavor. Since I aged the wine in glass, and bottled it in glass, the wine has almost always been in a reductive environment. Reduction here being used in the chemical sense, meaning that chemicals are stable in the wine that would not be stable in the oxidizing environment of the atmosphere. It also means that chemicals tend have a lower oxidation state -- that is have more electrons.
I had been thinking that bitter alkaloids were being oxidized upon contact with air.
A good reference on this is riojalta.com, where I learned a lot. Riojalta says that the reducing flavor is desireable; but I am not so sure. Also I think that the process of racking and bottling improves flavor, by allowing the wine a chance to oxidize a little.