Our olfaction receptors are situated in the nasal membrane and are stimulated by volatile chemical compounds, such as those found in coffee. These compounds come into contact with our receptors by being inhaled through the nose (as a gas by sniffing), or exhaled as vapors (when we swallow, the escape and rise to the receptors).
When we breath normally, the air doesn’t reach the olfactory membranes, where are receptors are located. But by sniffing or swallowing, we force air up the nasal passages through a series of membranes where odorous molecules are retained.
Because our individual olfaction is influence by things like our anatomy, physiology and psychology, the same coffee, served at the same time, can be perceived slightly different between people. People who cup loads of coffee often rely on odor memory created through years of experience rather than some hypersensitivity to aromatic stimulations.
When two or more olfactory stimuli are presented simultaneously, as is often the case when we ingest food and beverage, one of six results may occur:
- A single, new odor that blends the characteristics of each may be perceived
- When two dissimilar odors are presented, both may be noted, with first one and then the other being the focus of attention
- The odors may be smelled alternately
- The odors may be experienced simultaneously, but separately
- One odor may mask the other
- One odor may neutralize the other
In coffee, all of the above can take place simultaneously, which is why coffee has a unique aromatic character reminiscent of other familiar natural substances.
The aromatic compounds in coffee are classified by two methods. The first method is the separation of various components based on source. The second method sorts the components based on the similarity of molecular structure, principally by size, known as molecular weight. The use of these methods creates a set of nine categories to describe the aromatic profile of coffee.
