The fact that wine is a lot about chemistry has probably not escaped anyone. (After all, everything is chemistry.) However, you don’t need to know anything about chemistry to enjoy a wine. But sometimes you want to know where a particular aroma you feel on the nose comes from. What smells like raspberry, strawberry or tobacco does not, of course, come from these bushes but from an aromatic molecule in the wine.
An aroma that many people like in a wine is pepper and the molecule responsible is called rotundone (a terpene, a big family of aromatic chemical compounds) which is mainly found in the skins of the grapes.
Rotundone is easy to detect in the smell; the detection threshold is very low. However, studies have shown that between 20-25% of the population is incapable of smelling it. The rest of us, we mainly smell black pepper and white pepper.
Syrah is the grape that you might primarily associate with pepper, but there are a whole range of other grapes such as grenache, gamay, mondeuse, negrette and not least grüner veltliner in Austria.
Weather can affect the concentration of rotundone in the grape. A cool and humid growing season favours the concentration and high temperatures reduce the concentration (but UV rays can compensate).
Source: La Vigne.
(It may be worth pointing out that these chemicals compounds are naturally occurring and not something added to the wine. Virtually the only real flavouring used in wine is oak, usually in the form of oak casks for barrel ageing.)
For more information on this kind of things, aromas in wine, chemistry and so forth, see this.
