A small cup of coffee is all you need to get rid of your sleep during chilly winter mornings or tight exam schedules. But why is it that this drink full of caffeine which smells so delicious is not so luring while drinking. So, here is the answer.
The Coffee roasting process produces approximately eight hundred different compounds. These thermal degradation reactions decompose sugars and proteins to form the volatile compounds that we smell. Most of these reactions take place within the thick walls of coffee bean cells, which act as tiny pressure chambers. Green coffee tastes very grassy when brewed. You still get the organic acids and caffeine in the brew but it lacks the full sensation because there are few volatile compounds left due to lack of roasting.
Another reason that adds to the less pleasurable taste in the chemistry of the coffee bean. The roasting of these beans result in the production of eight hundred volatile molecular species of which aldehydes are the most delicate and volatile aromatic compound. This gives this hot beverage its sweet, caramel, fruit/floral like aromas. But exposure to air causes dissipation and the aroma vanishes. The most delicate aroma compounds found in this addictive drink are easily oxidised (changed into acid and water). This loss is accelerated when the process of grinding is going on. So, when you open the jar it is likely that the alluring smell is that of aldehydes and the equally volatile aroma compounds.
This all happens due to what scientists call “a second sense of smell”. Whenever we take a sip, the drink sends a burst of aroma from inside the mouth to the back of the nose, which in turn activates the sense of smell in the brain that is less receptive to the flavours causing a less satisfying sensation.
So, now we know that the why does coffee smell different than its taste.