The terms dark, medium and light roast, whoops, let’s reverse the order to light, medium and dark roast, describe the appearance of coffee beans when roasted for different amounts of time (if roasted at the same temperature). Light roasts are closer to the original coffee fruit (coffee cherry). Medium and dark roasts have been heated more profoundly at higher temperatures. These are relative terms and apply to different roasting levels for the same coffee bean. The original coffee beans can have different colors, so you have to know something about the original coffee bean if you want to describe the type of roast simply by looking at the color.
Light roasts, being closest to the original coffee bean, are light brown or tan in color, do not show oils on the bean’s surfaces, retain more natural oils, and volatile (easily driven-off by heat) organic compounds of the bean. They are higher in acidity than medium or dark roasts of the same bean. They retain more of the fruity flavors of the original beans. Caffeine is relatively stable to heating, so the amount of caffeine is not much different in light, medium, or dark roasts. However, as the coffee beans change in weight and volume during roasting(primarily due to loss of water and expansion of fibrous components), the amount of caffeine may be slightly higher in darker roasts when measured by weight but smaller when measured by volume. The temperature during roasting has been between 350-450 degrees Fahrenheit.
Medium roasts are darker brown, have less acidity and less of the fruity flavors, but have a fuller body, which is a function of the roasting process. Some oils may be visible on the beans.
Dark roasts are dark brown to nearly black and may show oils on the surface of the beans. Most of the original coffee’s flavor has been destroyed by roasting but has been replaced with a fuller taste due to the roasting process. Espresso beans are usually dark roasted blends. When the roasting period is extended further, burning occurs, and the coffee will have a burnt flavor. Temperatures of 450-500 degrees Fahrenheit have been used in the process.
Which one should you choose? It’s up to you, as everyone’s taste is different. So, try a few different ones and see what you prefer. Remember, the best cup of coffee is the one you like the most!