Coffee Roasting Process

Coffee Roasting

Coffee roasting is both science and art. The science lies in the chemical reactions and changes that take place during roasting that impact flavor. The art is taking that science and developing flavor profiles that are distinctive and delicious.

Hot air roasting or fluid bed roasting is an important part of the smooth, true flavor of Jamaica Coffee Trading Co coffees. Efficient heat transfer and removal of impurities are key.

Hot Air Roasting

A key part of our philosophy to coffee is exemplified by the fluid bed roasting method we have perfected over three decades. Originally developed by Michael Sivetz, the fluid bed roasting process, also known as hot air roasting, uses forced hot air to agitate and roast coffee beans. The perfectly controlled hot air flows over a tilted bed and circulates through the beans, roasting each bean evenly. This hot air reaches temperatures of between 450 and 485 degrees fahrenheit.

During the roasting process, the green coffee beans go through two major “pops” or “cracks” The first occurs when the internal temperature of the bean reaches approximately 356 degrees fahrenheit. By this point the silverskin or chaff has been expelled from the bean as it expands to double its original size. In the fluid bed roasting process, this chaff is blown out of the roaster into a separate chamber and not burned up with the coffee. Because coffee is so absorbent, if this chaff were burnt within the roasting chamber, the beans would soak up this unwanted flavor and present itself in the cup. In the same way, the hot air blows out any other impurities from the batch, so the only thing that is roasted and tasted is the coffee itself. This process of eliminating chaff and impurities is a unique and important aspect of the fluid bed roasting method that we employ each day.

Another advantage stems from the greater efficiency in heat transference that is possible with hot air roasters. The beginning stages of coffee roasting are focused on driving moisture from the bean; this moisture content can be as much as 12% by weight. The bean cannot actually be roasted until the moisture is removed, so this step is critical. When the coffee bean still contains this moisture, prolonged exposure to high heat results in “cooking” rather than “roasting” of the bean. The longer it cooks, the greater the formation of acids such as acetic and quinic. Since the fluid bed roaster can reach higher temperatures in half the time of typical cylindrical roasters, the time for these acidic compounds to form is greatly reduced. Many have found that these acidic compounds can cause stomach irritation, and we have many customers that had given up on coffee but can now drink ours comfortably.

Jamaica Coffee Trading Co coffees are characterized by a smooth, rich flavor that reflects the roast level and true essence of each bean.

Coffee Roasting Explained

Coffee roasting is both art and science. Our master roaster has over 2 decades of personal experience and collectively our roasting team has almost a century of experience between them. The unique advantages of our fluid bed roasting method means that we can roast more efficiently and cleanly than other methods. The result is a smooth, rich flavor that never tastes burnt or unnecessarily bitter. Our goal is a pure flavor that reflects the true essence of the bean. The efficient heat transfer possible with hot air roasting results in a quicker overall roast time.

Regardless of the roasting method, the process consists of alternating endothermic and exothermic processes or absorbing and releasing heat and stopping the roasting process through rapid cooling at precisely the right times.

Endothermic, Warm Up

During this “warm-up” process, moisture is quickly being dissipated. In the fluid bed method, this happens very rapidly, minimizing the formation of acidic compounds that are the result of moisture in the coffee bean exposed to high heat for an extended period of time. The aromas you would experience include wet hay or grass to toasted grain. The bean turns pale to tan to light brown to brown. The Malliard Reaction is key in the bean reaching a milk chocolate brown color. It is the same reaction that browns beef under heat.

Exothermic Reaction, First Crack

Up until this point, the bean is absorbing heat - endothermic. The first crack is the opposite; it is the release of heat energy - exothermic, and occurs when the bean has reached an approximate internal temperature of 401 degrees fahrenheit. The bean is now twice the size, has shed the majority of its silverskin or chaff and begins to release carbon dioxide. Pyrolysis is now occurring and will continue through the second crack; in other words there is a chemical change that cannot be reversed. The beans are dry in appearance with no oils visible. A Cinnamon or light roast is the beginning of the first crack.

Endothermic, Recovery

This brief stage after the first crack must be as short as possible so it does not to stall the roasting process. Around the 356 degree mark, caramelization of the sugars has begun and the continuation of this process is the difference between the bean being roasted or baked moving forward. In this case as in the warm-up phase, the fluid bed roaster has an advantage, adding heat more effectively to quickly move the bean to the second and final crack. Between the first and second crack is anywhere between 15 and 30 seconds, so heat transfer is critical.

Exothermic Reaction, Second Crack

The second crack or release of heat energy typically happens at an internal bean temperature of 437 degrees fahrenheit. From the first signs of the second crack to its completion can be a period of 25-45 seconds. Full City or Medium roast is at the first signs of the second crack. Continuing through the second crack results in Vienna, French and Italian roasts, progressively.

Cooling

At the appropriate roast level, it is critical to cool the coffee and stop the roasting process. In the worst case scenario, beans can be baked or burned after removal from the roaster. We continue our air-influenced process by using fans and vents to rapidly circulate cool air over the beans. The process ensures that accurate bean temperatures / roast levels are as intended.

Coffee Roast Levels

Roast levels are a function of time and internal bean temperature. As the bean temperature increases, it undergoes a chemical change accompanied by two releases of energy known as the first crack and second crack. Stopping the roasting process around these two events results in a range of commonly known roast levels. Apart from the underlying bean itself, roast levels can influence flavors in the cup. Generally, the darker the roast, the more the roast level influences flavor. At this roast level, the flavor characteristics of origin and processing can be identified and savored in the cup with minimal influence from the roasting process.

Cinnamon or Light Roast

This is the lightest roast and as the name implies, the beans are a deep cinnamon in color. The earthiness of the bean is forefront with wet grass, toasted grain and very bright character. The roast is stopped at the beginning of the first crack at an internal bean temperature is 383 degrees Fahrenheit.

Full City or Medium Roast

When the bean reaches an internal temperature of 427 degrees Fahrenheit, it begins the second crack. For a Full City roast, the roast is stopped right at the verge of the second crack at 428 degrees Fahrenheit. Typically, this roast is the best balance of time and heat to enjoy a coffee’s distinct origin with the roasting process unlocking as much of the organic compounds that define a coffee’s potential.

Vienna or Dark Roast

This roast is also known as a Light French Roast. The roasting process is stopped while the 2nd crack is underway and at this point the roast level begins to influence flavor. Distinct bitter sweet tones are present and acidity is neutralized. Internal bean temperature is 446 degrees Fahrenheit.

French Roast

Here the roast level overtakes the bean’s natural flavor. Beans are dark brown, and oil covers the beans. As the beans are roasted to higher temperatures, caffeine content drops. Roasting is stopped at the end of the second crack at an internal temperature of 464 degrees Fahrenheit.

Italian Roast

Approaching combustion, the beans are a very dark brown with burnt overtones coming to the fore. Oil covers the beans, acidity has been virtually roasted out. Internal bean temperature is 473 degrees Fahrenheit.