Coffee roasting transforms the physical and chemical properties of green coffee beans into roasted coffee products. The roasting process is the one that produces the aroma of the coffee, causing green coffee beans to change their taste. Unroasted beans contain similar, if not higher, sugars, proteins, levels of acids, and caffeine than those that have been roasted but do not taste like roasted coffee beans because of Maillard and other chemical reactions that occur during frying.
The vast majority of coffee is commercially roasted on a large scale, but small-scale commercial roasting has increased significantly with the trend towards "single-origin" coffees served in specialty stores. Some coffee consumers even roast coffee at home as a hobby, both to experience the flavor profile of the beans and to ensure the freshest possible roast.
The first recorded tools for roasting coffee beans were thin porcelain or metal pans, used in the 15th century in the Ottoman Empire and Greater Persia. In the 19th century, various patents were granted in the United States and Europe for commercial cakes to allow large batches of coffee. In the 1950s, just as instant coffee was becoming a popular coffee drink, specialty cafes began to open to satisfy the connoisseur, offering a more traditionally brewed drink. In the 1970s, several specialty cafes were established, offering a variety of steaks and beans from around the world. In the 1980s and 1990s, the gourmet coffee industry grew rapidly. This growth trend continued until the 21st century.
Roasting Coffee Beans
The first stage is endothermic. The green beans dry slowly to become yellow, and the beans begin to smell of toast or popcorn.
The second step, often called the first crack, occurs at about 205 °C (400 °F) where the grain doubles in size, becomes a light brown color and has a weight loss of about 5%. The appropriate Agtron number for this color is 95-90.
In the next stage, the temperature rises from 205 °C to about 220 °C, the color changes from light brown to medium brown and there is a weight loss of about 13%. The resulting chemical process is called pyrolysis and is characterized by a change in the chemical composition of the grain as well as the release of CO2.
The second step is followed by a short endothermic period which is followed by another exothermic step called the second fissure. This second pyrolysis takes place between 225-230 °C, and the color of the steak is defined as medium-dark brown. The second pop sounds much faster, and the beans get a greasy sheen.
The potential of the espresso is maximized when roasting when you maximize the sweetness and aroma of coffee while reducing bitterness and acidity. Most people focus on the latter and therefore fry extremely dark, but without sweetness and flavor, espresso will never be pleasant. This explains the unpopularity of straight espresso and the popularity of espresso drinks, in which either milk or other flavors are used to replace the sweetness lost by dark frying.
From 170-200 °C, the sugars in the coffee begin to caramelize. From the taste of pure sugar in relation to its caramelized component, it is obvious that non-caramelized sugar is much sweeter. The dark color of coffee is directly related to the caramelization of sucrose in coffee. Therefore, to maximize the sweetness, you want to minimize the caramelization of sucrose, but do not want to fry too lightly or bitter-tasting compounds will not degrade thermally. Do not fry anywhere between the end of the first crack and less than half of the second crack. Do not fry well or pass the second crack. We recommend a frying room temperature somewhere between 205-215 °C. Realizing the danger of the following suggestion, we recommend a color similar to the one below.