Reference point
Open a bag of freshly roasted coffee beans and smell as soon as it is opened.
Do this before you read on. An entry only works when you have just smelled the thing.
Burnt-sweet, with a smoky note, a chocolate note and a faint sourness. Very complex — roasted coffee contains hundreds of volatile compounds, more than almost anything else in the dictionary.
That makes it a good entry for practising a different skill: accepting that some smells cannot be separated into their parts by the bare nose and can only be described by direction and by layer.
Light and dark roasts give two quite different profiles. A light roast keeps the sourness and the fruity notes; a dark roast loses them and keeps only smoke and chocolate.
How to smell it
Open a bag of freshly roasted coffee and smell at once. Wait seven days and smell the same bag again — most of the volatile compounds have gone, and you will understand why coffee lovers care about the roast date.
Why this one is hard
Because the complexity is too high. This is an entry to save for later, once you are used to simpler smells.
Don’t confuse with
This entry
Roasted coffee
Gourmand family
Both are products of fire. Coffee has furfurylthiol, which gives its characteristic sulphur note; scorched rice crust is pure Maillard, sweeter and without that note.
Scientific note
Roasted coffee contains more than eight hundred identified volatile compounds, more than almost any other food. Only about thirty of them actually contribute to the smell people perceive; the rest lie below the detection threshold. It is the best illustration of the principle that the number of components says nothing about intensity.
There is an apparent contradiction on the volatility band. Roasted coffee is placed in the base stage, yet 2-furfurylthiol — its key marker compound — boils at only about 155 degrees.
It is the same phenomenon as in foods that have been through fire or fermentation: the compound that lets you recognise the smell is light, while the body of the smell is heavy. Furfurylthiol is what says “coffee” in the first second, and also what is lost fastest when coffee is left open. What keeps a cup of coffee smelling after half an hour is the heavier furans and higher Maillard products, mostly too heavy to evaporate early.
In Vietnamese life
Vietnam is the world’s second-largest coffee exporter, almost all of it robusta and almost all of it as green beans. Much of the value lies in roasting, and that mostly happens in other countries.