What is Roasting?

The coffee roasting process is the activity of roasting green coffee beans by a roaster, using a coffee roasting machine at a roasting temperature of around 180 – 250 °C, which is gradually increased and heated for 7 to 20 minutes according to the desired roast level. The coffee roasting phase itself consists of several stages, starting with drying, yellowing, first crack, roast development, second crack, and then repeating the next stages.

The Maillard reaction that occurs when coffee is roasted gives time for the flavor and color compounds of the coffee beans to begin to develop and are further explored. In the early stages of roasting at temperatures between 150-200°C, derivatives of sugar compounds and amino acids in the coffee begin to react, forming aroma and flavor compounds. More specifically, the Maillard reaction, also known as caramelization, changes the color of the raw coffee beans from green to brown.

The Maillard reaction phenomenon is not only found during the coffee roasting process, but is also commonly encountered in the food and beverage industry, such as in cooking, baking, and similar processes. The derivative compounds of sugars and amino acids in food ingredients like meat, vegetables, nuts, and other materials, when heated, will respond by enhancing flavor and changing color. This reaction was discovered by the French chemist Louis Camille Maillard, and to this day, some people use the Maillard reaction as an indicator of the level of doneness in cooking, baking, and similar processes.

Light Roast

Light roast coffee is a roasting level that has a soft flavor profile. It is roasted at temperatures around 180-205°C. During the light roast process, the coffee beans turn light brown with a high caffeine content, and the oil sheen on the surface is not very visible.

For those who enjoy coffee with a tea-like texture and a gentle character, light roast is the perfect roasting level. You can check the coffee beans you buy to determine the roast level. Lightly roasted beans will generally not only appear as the "youngest version" of brown coffee, but there will also be no noticeable oil sheen on the surface of the beans.

The longer the coffee beans are roasted, the more oil will appear on the surface. Since light roasted beans are typically roasted for a shorter period—and sometimes at lower temperatures—the coffee oils haven’t had enough time to surface.

Medium Roast

Medium roast coffee is the roasting process just above light roast, with the coffee beans roasted at around 210°C. The resulting color of the coffee beans is brown during this process, and medium roast is the most common level for manual brew coffee preparations.

The texture is somewhat similar to tea and is a step "more tanned" than light roast. Almost like light roast, if you look at coffee beans roasted at this level, you won’t find any noticeable coffee oil on the beans. However, if you try two cups of manually brewed coffee, one roasted light and the other medium, you will definitely taste the difference.

Coffee roasted at the medium level tends to have a more intense flavor compared to light roast, but it’s still not as strong as dark roast. Because it balances flavor and composition perfectly, it’s no surprise that this roast level is quite popular among many roasters.

Medium-dark Roast

Medium-dark roast coffee is a roasting level that delivers a stronger, more intense flavor character, with roasting temperatures around 225°C. During the roasting process, medium-dark roast beans begin to show an oil sheen and turn slightly darker.

Next in the flavor spectrum is the medium-dark roast. This level brings a heavier body and more intense flavor to the coffee. Beans roasted at this level usually show an oil sheen on the surface of the beans. When brewed, it also forms a pleasant balance of bitter-sweet character.

Dark Roast

Dark roast coffee is the darkest roast compared to light and medium roasts. The oil on the surface of the coffee beans is clearly visible. The roasting temperature for dark roast is typically above 225°C.

Dark roast coffees (and even darker levels like Italian, Vienna, or French roast) are generally prepared when the coffee will be blended with milk, sugar, or other ingredients to make drinks like cappuccinos, lattes, flat whites, etc. It's very rare for a manual brew coffee to use this roast level. Dark roast coffee, at its core, almost loses any original flavor character except for a burnt, bitter taste. If any original flavor does remain, it’s usually very faint.