Coffee Roasting: the art of blending and perfect roasting

Coffee roasting is an ancient art and a scientific process that requires precision and expertise to transform flavorless green beans into one of the most beloved products in the world. This article examines the process starting from blending different varieties of green coffee beans up to the actual roasting, describing the physical and chemical mechanisms that define the sensory characteristics of every cup.

Blending the varieties of green coffee

The first step in coffee roasting is the selection and blending of green coffee beans. This step requires experience, as each variety, whether it be Arabica, Robusta, or other less common species, contributes different organoleptic properties in terms of acidity, sweetness, body, and aroma.
Professional roasters carefully select the origins of green coffee, taking into account factors such as altitude, climate, and soil of the growing region.

The focus is mainly on Arabica and Robusta coffee.

• Arabica: Typically more delicate, with higher acidity and fruity or floral notes.
• Robusta: Fuller-bodied, with a higher caffeine content and notes of dark chocolate or spices.

Blending balances these qualities, creating unique aromatic profiles that meet specific market tastes. Some roasters prefer to blend green coffee before roasting (raw blending), while others mix the beans after they are roasted (hot blending). The choice depends on the characteristics they wish to achieve and the level of control desired over each component of the blend.

Roasting: From green to gold

Once the blend is prepared, the actual roasting process begins, which involves exposing the beans to high temperatures, generally between 180°C and 230°C. The process occurs in several stages, during which the beans undergo physical and chemical changes that determine their final color, aroma, and taste.

Drying phase

Green beans contain about 10-12% water. During the first few minutes of roasting, the water evaporates, making the beans ready for the subsequent chemical development. The color of the beans starts to change, shifting from green to yellow.

Maillard Reactions

One of the most important stages of roasting is the Maillard reaction, an interaction between amino acids and sugars that occurs at about 150-160°C. This reaction is responsible for developing many of the coffee's complex aromas, such as notes of caramel, dried fruit, chocolate, and spices. Strict temperature control is essential, as too fast reactions can lead to over-roasting, while a slow process may reduce the intensity of flavors.

Sugar Caramelization

When the temperature reaches around 170-200°C, the sugars in the beans begin to caramelize. This process contributes to the coffee's sweetness and body. At this point, the beans turn from yellow to light brown, and the characteristic aroma of coffee begins to emerge.

First Crack

At 200-210°C, the beans undergo a rapid physical expansion known as the "first crack." The heat causes the gas inside the bean to increase pressure, resulting in an audible pop. This phase is critical: roasters must decide whether to continue for a darker roast or stop to preserve more delicate aromas.

Roasting control: The roaster's role

The success of a roast largely depends on the experience and skill of the roaster, who must be able to control critical variables such as temperature, time, and airflow within the roasting machine. Even small changes in these variables can lead to different results.

• Temperature and time: Balancing temperature and roast time is crucial. A fast roast at high temperatures can highlight aromatic notes but risks burning the beans, while a slower and more controlled roast allows for better flavor development.
• Airflow: Airflow helps remove smoke and gases emitted during the process, preventing them from affecting the flavor of the coffee. It also manages heat dissipation, preventing over-roasting.

Cooling and Degassing

After roasting is complete, the beans must be rapidly cooled to stop the cooking process. Cooling is done by air immediately after opening the roaster chute and releasing the beans.
After cooling, the roasted coffee enters a degassing phase, resting in silos where it releases carbon dioxide. This step is important because the gas can affect extraction during coffee preparation and cause issues with vacuum-packed containers, leading to package swelling.

"Manaresi" roasting: The right balance

We opt for a medium roast, avoiding oil release while preventing the beans from becoming too amber, which can make them overly acidic, as sometimes requested by Eastern and Northern European countries that prefer long-brew coffee.
We believe in the right balance, between Arabica and Robusta, between too light and too dark a roast. This is certainly our recipe for the coffee that Italian families love, and we proudly interpret it.

Coffee roasting is a complex process that requires a deep understanding of the chemical and physical reactions involved. Combining different varieties of green coffee, precisely controlling the roasting temperature and time, and sensing the right moment to stop the process are all essential skills for achieving a superior quality coffee.