Why Coffee Smells (And Tastes) So Good
DON BRUSHETT 31 DECEMBER 2014 11:30 AM
Welcome to our three-part series Chemistry of Coffee, where we unravel the delicious secrets of one of the most widely consumed drinks in the world. So while you enjoy your morning latte, long black or frappe, read on to find out why it tastes so good — you might be surprised to discover what’s in your cup.
Most of what we taste we actually smell. The only sensations that we pick up in our mouth are sweet, sour, bitter, umami and salty. Without its smell, coffee would have only a sour or bitter taste due to the organic acids. Try it with your next cup of coffee — hold your nose as you take your first sip.
The rich satisfying sensation of coffee is almost entirely due to the volatile compounds produced when we roast coffee beans.
The compounds that are formed in the roasting process are very similar to any other compound that is formed in the cooking process. The smell of baking bread is from compounds produced when a sugar reacts with a protein in what is called a Maillard reaction.
Not every scent is as welcoming as freshly baked bread, though. Our sense of smell has developed over millennia to detect dangerous compounds.
Cadaverine and putracine, produced in rotting meat, can be detected by our nose at very low concentrations. The same can be said of sulphur-containing compounds such as hydrogen sulphide — rotten egg gas — which is detected by our nose at levels of parts per billion.
The upshot of this is that we do not detect all compounds in our surroundings to the same extent. For example, to us water is completely odourless although it may be very concentrated in the atmosphere.
Odour chemists have developed a system called odour activity values which show how we respond to particular compounds. This has an influence on how we experience a complex mixture of stimuli.