Coffee roasting involves four key steps: Roast, Grind, Brew & Tear. Roasting takes place at temperatures ranging from about 200°F to 400°F. A properly roasted bean will have a dark brown appearance and should smell like chocolate. To determine if coffee is fully roasted, simply run your finger through the top of the cup — if it feels gritty, then your coffee is not yet roasted enough. Coffee grinders vary widely in size and type, so we recommend finding one that works best for you. For an easy beginner recipe, try our Espresso Bean Latte with Cinnamon Roll Cookies.
Green coffee beans must be roasted before you can enjoy them. Roasting exposes the natural flavor in the coffee and allows the beans to become fragrant and delicious.
Coffee roasting steps:
Slow Heat Up:
Green coffee beans are first placed in a roaster. Once the roaster reaches its target temperature, the beans are tumbling like clothes in a dryers to allow the heat to penetrate slowly to all of the beans. As the temperature rises, it will start heating the beans unevenly. The temperature is then slowly increased to about 460°F to 530°F. This allows the heat to penetrate slowly through the beans, helping them cook evenly.
Coffee Color Change in roasting:
First Color Change:
After the initial roast, green coffee beans contain a significant number of water molecules. When the temperature increases during the roasting process, the coffee beans release a large amount of steam through the pores on their surface. The beans start turning yellow and then begin to brown.
Second Color Change:
Red coffee beans are also initially quite moist, but after the roasting process, they begin to dry out significantly. This causes the beans to darken in color and become harder.
Third Color Change:
Black coffee beans are roasted at lower temperatures, resulting in a darker roast compared to other coffees. During the roasting process, black coffee beans continue drying out, causing them to darken.
First Crack step:
First Crack is when the coffee bean swells (increases in size) and begins to burst out of its shell. You hear a loud cracking noise just before the sugar starts to caramelize and the roasting process begins. First Crack occurs when the coffee bean is still raw.
During the roast, the bean expands due to heat and pressure. The heat causes water molecules within the bean to expand. As the beans continue to cook, the surface layer separates from the interior. This causes the outer layers to contract and push against the inner layers. This creates cracks in the exterior of the bean. After first crack, the bean continues to roast until the final stage of the roast, called second crack.
Rapid Second Color Change:
After the first crack, the caffeine starts to dissolve the proteins in the coffee bean. As a result, the coffee becomes darker. When the liquid inside the bean evaporates, the surface area increases dramatically. This allows the heat to reach deeper layers within the bean, causing the inner parts of the bean to start to cook and change color.
Second Crack:
Second Crack is a loud crack that happens after the first crack. Roastmasters often wait until the second crack to start pulling the beans out of the roaster, because the second crack is harder to identify than the First Crack. By waiting until the second crack, you get darker roasted coffee. When the second crack is desired, the coffee is darkly roasted and tastes bitter.
Stopping the Roast:
Roastmasters use smell and color to judge when the coffee is ready. Some roasters use an instrument called a thermocouple to measure the temperature inside the roasting chamber. A thermocouple is similar to a thermometer, except that it measures temperature instead of pressure. Thermocouples are often used in combination with other devices to accurately measure the temperature inside the chamber. Roasters also use timers to measure the length of time required for particular temperatures to reach. Timers allow the roaster to predict when the coffee will be finished and remove it from the oven before it overcooks.
Degassing After Roasting:
After the coffee is roasted, it goes through a process called degassification. This happens for about 24 hours after roasting. During this time, the coffee releases carbon dioxide. If you grind or brew the coffee before this time period, you will lose flavor because the coffee won’t release its CO2. You need to wait at least 24 hours to get the best taste out of your coffee.
Source: caffeinepark.com
