I infrequently drink more than one cup of coffee a day (and always black)–usually because my enjoyment increasingly diminishes to the point that I don’t finish my cup. I have always perceived my coffee to be primarily an olfactory experience with secondary pleasures directed towards either the warmth or the flavour complement to some other food. And, since the olfactory system becomes desensitized to most odors (excluding ones that serve as warnings), my lessening enjoyment makes sense. The exception is my weekend morning cup which I usually do finish.
A study published in the Journal of Agriculture and Food Chemistry found that the volatiles in coffee berries themselves (the study used Coffea arabica, or Columbia) are dominated by high levels of ethanol, except overripe berries which are dominated by esters (as might be expected with any overripe fruit). Interestingly, the largest number of chemical compounds were detected in the overripe berries.
Another study published in 1960 on the volatiles of roasted and ground coffee found 158 compounds. When added to previously identified volatiles, the number jumped to 318, suggesting that coffee aroma is too complex to be fully captured by a few key odors. Half a century later, the problem of finding key volatiles persists. Two studies published in 2010 (in Chemometrics and Intelligent Laboratory Systems and in Analytical Chemistry) noted that the trouble is the high number of volatile peaks that occur when analyzing the compounds–roughly 300 volatiles in green beans to over 1000 in roasted beans. Coffeeresearch.org compiled data for what might be the strongest contribuuters to aroma, noting that furans have a dominant role and contribute the caramel-like note in many coffees.
“A coffee’s aroma will vary as a function of changes in soil, microclimate, altitude, types and species of bean used, the roasting process, and the preparation of the coffee. These various conditions affect the concentration and composition of the various aroma volatiles, which include carboxylic acids, alcohols, aldehydes, alkanes, alkenes, aromatics, esters, furans, ketones, lactones, oxazoles, phenols, pyridines, pyrazines, pyrroles, thiazoles, and thiophenes.”–from the 2010 Analytical Chemistry publication above by Susslick
Such a complex odor that creates a person-specific experience…however and whenever you like your coffee, take a moment to appreciate it’s complex nature that has stymied normal methods of detecting and synthetically creating odors.