In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance’s vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.
In specialty coffee, volatility is particularly important because coffee taste and aroma are influenced by certain compounds that are relatively volatile. The more volatile the compound is the faster it will vaporize. This is why the coffee brewing temperature is so important; it allows proper and fast extraction of nonvolatile components, while preserving the volatile ones. Espresso extraction is a few degrees lower than drip coffee. Pressure helps extract more TDS at a lower temperature, while preserving volatile components.