How a coffee bean is roasted is one of the most important factors in determining its flavor. Whether you’re brewing for customers or for yourself, knowing how roasting affects coffee is fundamental to its enjoyment.

Here are some quick tips: 

• The amount of caffeine in the bean decreases as the roast gets darker.
• The surface of lightly roasted beans is dry. As roasting increases, the oil in the beans is drawn to the surface where it becomes visible.
• Roasting decreases acidity in the beans, therefore darker roasts are less acidic.
• The darker a bean is roasted, the less prominent the distinct flavors of its origin become.
• Medium roast beans tend to have the heaviest “body.” Light and dark roasts have less.

Roast names and descriptions are not uniform. Some processors have more levels of roasting than others, and nearly all have their own names, often more for branding than for information. So when selecting a roast, it’s better to go by the actual roast level than a fancy title. Here are the most common roast levels.

Light Roast

Highest in caffeine content, light roasts are dry on the surface, light in body, acidic, and have a toasted grain, or even grassy, taste. The origin flavors are more pronounced in light roasts than at other levels.

As beans are roasted, they expand, causing the outer shell to crack. Since light-roasted beans typically reach an internal temperature of 205°C (400°F) or less, they pop or crack only once. Thus you may hear them described as “first crack” roasted. Some of the descriptive terms for light roasts are Light City, Half City and New England roasts.

Medium Roast

Medium roasts appear darker but are still dry on the surface. The higher roasting temperature reduces the grainy taste of lighter roasts and makes for a more balanced, less acidic taste. Native tastes start to become masked by the higher-temperature roasting as the flavor becomes toastier. The caffeine level is somewhat lower than light roasts but still higher than darker roasts. Reaching an internal temperature of around 220°C (428°F), medium roasting stops just before starting the second crack of the bean.

The most common roast in the eastern United States that you’ll find is medium roast, sometimes called American Roast, Regular Roast, Breakfast Roast and City Roast.

Medium-Dark Roast

Medium-dark coffees are roasted to 225°-230°C (445°F), which is the beginning or middle of the second crack. They have a darker, deeper color and some oil on their surface. They have a heavier body and more roasted flavor and aroma, sometimes even with spicy undertones, and slightly less caffeine than medium roasts.

Common descriptions of medium-dark roasted coffees are Vienna Roast, Full City Roast, and After Dinner Roast.

Dark Roast

As the name implies, dark-roasted beans are dark brown to nearly black in color and have an oily sheen on their surface. Their coffee can have a smoky, bitter or burnt taste and is significantly lower in caffeine than lighter roasts.

Dark roasts reach an internal temperature of 240°C (465°F), at or beyond the point of the second crack in the bean’s surface. Much hotter than 240° can result in tarry or charcoal-like flavors. Dark roast is often used for espresso and Turkish blends. You may find dark-roasted coffee going by French Roast, Spanish Roast, New Orleans or Continental Roast or Espresso.

Of course there are other factors that influence flavor and aroma of coffees, and ultimately it’s a matter of personal taste. Experiment to find the ones that are right for you and your guests.