Most coffee drinkers drink either medium or dark roast coffee. The most basic difference between the two is that a dark roast is roasted longer than a medium roast. As such, the coffee beans have a strong coffee flavor which is suitable for milk based coffee drinks.
Beans roasted to medium-dark reach an internal temperature of 437°F – 446°F. This is during or just after the second crack. This roast will also start showing the oils on the beans’ surface because the temperatures are high enough. With a medium roast, you’ll be more able to taste the distinct characteristics of whatever type of coffee bean was used to make your coffee. With dark roast, the roasting process standardizes much of the flavour.
The roasting temperature for a dark roast is between 464°F – 482°F. There are visible oils on dark roast beans. Typically you cannot taste any origin flavors in a dark roast, just the affects the roasting process has on that type of coffee bean. Dark roasts have sweeter flavors because the sugars in the coffee beans have time to caramelize. The longer roasting process helps it to develop a richer flavor and full body, which often leads to it having a buttery finish. They also have the least acidity of all coffee roasts. Dark roasts have the least amount of caffeine because they’re roasted the longest.