Roasting coffee beans unlocks the aroma and flavors inside the raw green coffee beans. The roasting starts a chemical reaction as the beans are rapidly brought to extreme temperatures. When the beans reach the appropriate roast, they are quickly cooled to stop the process. These now Roasted beans smell more like the coffee we know and love. They roast the medium dark roast coffee beans until they are a dark brown color.
The first crack is a coffee roasting term to describe the audible cracking sound when roasting a coffee bean. This audible cracking sound signals that the bean is approaching edibility. The crack happens because the coffee beans have expanded and the moisture has evaporated and the resulting pressure causes the bean to crack open. There are two cracks during the roasting process, and light to mediums roasts finish between the two cracks. The light roasts, roasted until just after the first crack when they visibly change color and crack.
The second crack is a coffee roasting term to the describe the second audible cracking sound when roasting coffee beans. Second crack is when the beans release increasing amounts of oils and begin to smoke a lot. The internal temperature is above 350 degree Fahrenheit now. If the roasting continues beyond this point, the beans will darken further.
Medium dark roasted beans reach an internal temperature of 437°F to 450°F. The beans pop or crack while giving off oils and smoke. We know this as the second crack. Therefore, a dark medium roast is a coffee bean that’s roasted to the beginning of, or middle of the second crack. Medium dark roasts are much dark brown color with a heavier body, there are oils on the surface of the beans. The medium dark roasts have a medium body strength and medium acidity. The origin flavors of the bean become more of an overtone with a caramel sweetness taking effect the longer roasting process. Some Medium dark roasts have a spicy flavor however, it relates this to the region of the origin bean. The Medium Dark roast has less caffeine the medium roast, with longer roasting always resulting in less caffeine retention.
More common roast names within the Medium Dark Roast category are Full City Roast which is Roasted to Beginning of the second crack and Vienna Roast which is sometimes considered a dark roast is roasted to mid-second crack.
The full city is a darker roast the city roast the beans roasted to just prior to the second crack. With small amounts of oil, however, mostly dry.
Vienna Roast is darker roast in color and flavor with a smoky aroma and an almost dark chocolate taste.