Professional coffee roasting knowledge Coffee roasting concepts and principles

Roasting, as the name suggests, provides heat to coffee beans, causing a series of chemical changes to occur within them. Green coffee beans through roasting, showing coffee unique color, flavor and taste. Each coffee bean contains flavor, sourness, sweetness and bitterness. How to release them depends on the roasting temperature.

Roasting is an important step in the long journey of each coffee bean, from the bland green bean to the lingering aroma of the cup. Coffee beans in this field for about 20 minutes (inversely proportional to the temperature), temperature as high as more than 200 degrees Celsius, in the process of intense dialogue with the fire, through many chemical changes. First of all, starch in raw beans will be converted into sugar and acidic substances due to high temperature, while cellulose and other substances will be carbonized to varying degrees. Water and carbon dioxide evaporate, and protein is converted into enzymes, which combine with the rest of the fat to form an oil film on the surface of the beans. Coffee beans expand during roasting, making a pop-like noise and losing moisture. But because the outer skin of coffee beans is very tough, we usually don't see coffee beans crack like popcorn. From raw beans, light roasting, medium roasting to deep roasting, water is released again and again, weight is reduced, volume is slowly expanded, color of coffee beans deepens, fragrant oil is gradually released, and texture becomes crisp.

Green beans contain a large amount of chloric acid, which gradually disappears during baking, releasing familiar and pleasant fruit acids such as acetic acid, citric acid and malic acid contained in wine. Baking is beneficial to present these acids in moderation.

We often see roasted coffee beans with different shades of color, on the one hand, this may be due to different types of single-serve coffee beans; on the other hand, the main reason for this color difference is the degree of roasting. In the most colloquial language, the degree of roasting can be interpreted as the degree of heat at which it is baked. To take the classic example of carbon-roasted coffee, this is a French roast in which the beans are highly carbonized, dark brown in color and carbon black in color due to the depth of the roast (either due to the high temperature of the roast, or due to the length of the roast, or both, depending on the circumstances). Carbonized coffee is generally believed to taste bitter, not only from caffeine, but more from carbonized coffee beans.

Principles of baking: The most important thing about baking is to be able to cook the beans evenly inside and outside. First of all, the water in the beans will be smoothly discharged through the fire. If this step is too hasty, it will have spots and taste astringent.

Eighty percent of the taste of coffee depends on roasting, so roasting is an important process in brewing good coffee. If the baking technique is good, the beans will be large and swollen, the surface will not be wrinkled, and the luster will be balanced. Roasting coffee beans to their ultimate character is the ultimate goal of roasting.

The flavor of coffee depends not only on the variety of coffee, but also on roasting.

Basically, coffee roasting is a high-temperature coking process that completely changes the substances inside the green beans, producing new compounds and recombining them to form aromas and alcohol flavors. This effect only occurs at high temperatures, and if only low temperatures are used, decomposition cannot be caused, and no matter how long the coffee beans are baked, they will not be cooked.