Finding the right roast profile for the maximum enjoyment of each individual coffee can and should be half the fun. The coffee industry has no set roast profile and roasts vary from roaster to roaster. Since you are now are considering being a home roaster and will soon develop your own interpretation of roasts and what serves you best, here are some guidelines for your journey
The first of two distinct pyro lytic reactions in roasting coffee. First crack is distinguished by a loud cracking or popping sound and occurs in most roasters between 390 – 410 degrees Fahrenheight. It has sound similar to the popping of popcorn. First crack marks a rapid expansion of the seed and the point where water and carbon dioxide fracture, leading the liberation of moisture in the form of steam. This process opens the crease in the bean just enough to release the remaining silver skin in the form of chaff.
City Roast Levels
This is the earliest palatable stage that the roast can be stopped and result in good tasting coffee. City roast occur between 412 – 425 degrees on most roasters. At this roast level the origin flavor is not eclipsed by roast flowers, but the risk is that sourness, astringency, or under developed sweetness can make the cup unpleasant.
City Roasts generally have a light brown color with strong surface texture, even dark creases in the bean surface and only moderate expansion of bean size. This varies greatly in different coffees, though. As a very general rule to achieve City roast the coffee is removed from the heat at the last detectable sound of first crack or very soon after with no development towards 2nd crack.
This roast level is often used for cupping as it unmasks the most characteristics while allowing for the beans individual profile to be exposed. Some coffees at this roast level will brighten up a blend.
City + Roast Level
This ideal roast level. also called a medium roast, occurs roughly between 425 – 435 degrees F on most roasters. The coffee has been allowed to develop anywhere from 10 seconds to 1 minute or more, depending on the roast method after the last “POP” of first crack. These times and heat ranges vary depending on the roast flavor and the origin of the green coffee.
At this level their is a balance between moderate roast flavor and the origin flavor of the bean. Astringent, sour or “baked” light roast flavors a re reduced, yet the flavors specific to a particular coffee lot are still expressed in the cup. City + roasts have a medium brown color and may not yet have the smooth surface that with further development towards 2nd crack
Full City Roast Level
Full city is right at the brink of 2nd crack, roughly between 435 – 445 degrees F. At this roast level, certian qualities of the origin might be best experienced when the roast flavors are actually greater. Many Sumatran coffees fall into this category. Full city roasts have a much more uniform dark brown color and have a smooth surface from the browning and bean expansion that occur as the coffee is on the brink of Second Crack
Second Crack is the second audible clue the roaster/operator receives about the degree of roast. Whereas first crack sounds like popcorn cracking, second crack has a faster shallower patter, much like rice Krispies in milk. Second crack is a farther stage of the pyro lytic conversion of compounds and occurs around 440 – 450 Fahrenheight. This is a physical fracturing of the cellular matrix of the coffee and results in a eventual migration of the oils from their chambers within the coffee to the outside of the bean, When 2nd crack is volatile enough, it can blow small discs off the coffee bean.
The most popular of the dark roasts, French roast is achieved when you allow the roast to continue into the 2nd crack until the beans are very dark and very oily.
Italian or Espresso Roast
The roast most often used in making espresso drinks shots of espresso. Not all of the dark roasts make a great espresso but should be tried to see what suits your pallet. Italian roasts is achieved when you allow the beans to roast to almost black, very oily and beyond French Roast. As the roast gets darker they speed up considerably so the difference between a French Roast and an Italian roast is only seconds when roasting.
Temperatures given are general and relative to the quality and placement of the thermo-probe. They are not the absolute truth for all roasters. If your roaster cannot measure the temperature – don’t worry. Use all your senses to judge the sight, smell, sound and more importantly the taste of the roasted coffee.