Coffee Roasting

The green coffee bean, like other nuts, kernels and beans is a combination of fats, proteins, fiber and miscellaneous other substances. The aroma and flavor of coffee appears only when heat is applied to the bean simultaneously drawing out the moisture and base matter in the beans a volatile, oily substance variously called coffee essence, coffee oil, or coffeol. It is a fragile substance that evaporates easily and absorbs less undesirable flavors. Without this, there is no coffee, yet it constitutes only 0.5% of the weight of the bean.

As the bean is held in the roaster for longer periods and more moisture is lost, the oil develops further and some begins to rise to the surface of the bean, giving dark roasts their characteristic lightly slick to oily appearance.

Beneath the oil, the hard matter of the bean begins to develop a slightly burned flavor while the sugars caramelize, which together help create the bittersweet tones so attractive to dark-roast aficionados. When most of the sugars have been burned off the resulting roasted coffee is called French or Italian. Darker roasts contain a touch less caffeine than lighter roasts. Coffees are roasted across the whole spectrum of where moisture and the coffee oils are released.