A book that I own called Chemistry and Cookery, published in the 1930s, has a great section about coffee that is fun to read as a chemistry book and as a piece of history. It has a big section about coffee preparation methods, all written well before most people were drinking coffee brewed with an automatic drip coffeemaker, let alone having access to espresso.
The discussion includes frequent reference to an oil called caffeol, which the authors refer to as a volatile oil that is easily lost through extended heat, boiling, or long storage especially in an open container. What is this caffeol, I wondered, and why do I not hear it referred to by those who wish to advertise their beans as the best available?
I went to Wikipedia. I found a single mention of it as a volatile oil responsible for flavor and aroma in coffee, but with no structural information.
So I googled "caffeol." I found numerous references to it as a volatile oil responsible for flavor and aroma.....no structure.
So I googled "caffeol structure," and found a book excerpt (thank you google books!) from Coffee Flavor Chemistry by Ivan Flament and Yvonne Bessier-Thomas that actually gives caffeol a bit of attention.
What do they say? Lots. It takes several pages (starting at about page 61), and they're complicated and it's late and the story is long and meandering. But what grabs me as I look at the pages from the book is that there are two tables listing what must be about 20 compounds identified in coffee aroma. I also know nobody has managed to bottle an artificial version, so we have probably not worked out the composition of the entire mixture. Nothing smells quite like the real thing.
I am putting that book on my Christmas list.