Chemical reaction of Coffee in roasting

Coffee has a rich, wide range of flavors. Coffee produced in different regions, different elevations, different climates and different producing areas has its own unique characteristics. Raw beans are fragrant and have no usual coffee taste at all; the taste of coffee comes from proper roasting. Show fruity (light roasting) or caramel sweetness (deep roasting). The shallower the baked, the more sour the taste, and the deeper the baked, the more bitter the taste.

Raw beans in high temperature environment, through thermal decomposition, coffee raw bean components such as chlorogenic acid, protein and fat undergo a series of chemical changes (mainly Mena reaction) to produce coffee aroma substances. including aldehydes, lipids, ketones, acids and so on.

When the bean temperature > 100℃, the color of raw beans changes from green to yellow, and when the moisture is on, it is lost for dehydration, resulting in a smell similar to that of baked bread.

Bean temperature > 120,130 ℃, raw bean color changes to light brown.

The bean temperature is about 150℃ to produce the smell of stir-fried barley.

The bean temperature is about 180 ℃ and begins to produce green smoke. The first explosion begins to produce chemical pyrolysis reaction, which releases a large amount of CO2. The burst sound occurs, the color turns brown, and the size of the bean increases.

The bean temperature is about 210 ℃, the first explosion is over, and the color continues to darken.

The second explosion of the bean temperature was about 220℃ ~ 230℃. The color continued to become dark and dark brown, and oil appeared on the surface of the coffee bean.

The bean temperature is about 240℃ ~ 270℃. Although the temperature increases, the darker the bean color, the more gas is released, the volume continues to expand, the coffee bean surface oils out, and the coffee aroma changes fully.

The bean temperature is about 270℃ to stop releasing smoke, the color is black, the appearance becomes dark, and the volume is no longer larger.

The bean temperature is about 300 ℃. The beans are black, puffy and fragile, and the aroma disappears completely and becomes carbonized.

The general actual baking temperature range is 185-240 ℃. In addition to the influence of temperature on the flavor of coffee, the way and equipment of roasting also have an effect.