What is the meaning of roasting coffee beans? The three stages of roasting coffee beans

The significance of coffee roasting

Basically, coffee roasting is a kind of hot Pyolysis roasting that completely changes the substance inside the raw bean, produces new compounds and recombines to form aroma and mellow flavor. This effect only happens at high temperature, but it cannot be decomposed if only low temperature is used, no matter how long the coffee beans are roasted.

Most people think that baking is nothing but cooking raw beans with fire. In fact, roasting is the most difficult step in the processing of coffee.

Baking can be divided into three stages:

(1) drying

(2) High temperature decomposition

(3) cooling

(1) drying

In the early stage of baking, raw beans begin to absorb heat, and the internal water gradually evaporates, when the color gradually changes from cyan to yellow or light brown, and the silver film begins to fall off, and a faint smell of grass can be smelled. This stage is mainly to remove moisture, accounting for about half of the baking time.

Because water is a good heat transfer conductor, it helps to roast the internal substance of coffee beans, although it is removing water, but the baker will make good use of the temperature of the water and properly control it so that it will not evaporate too fast. usually, it is best to control the water to reach the boiling point at 10 minutes and change to steam, when the internal material will be fully cooked and the water will begin to evaporate out of the outside of the coffee beans.

(2) High temperature decomposition

When the beans are roasted to about 160 degrees Celsius, the water inside will evaporate into gas and begin to blow out the outside of the coffee beans. At this time, the inside of the beans will change from endothermic to exothermic to produce the first burst sound. After the bursting sound, it will turn to endothermic, and the pressure inside the coffee bean is extremely high, reaching 25 atmospheres.

High temperature and pressure begin to deconstruct the original tissue to form new compounds, creating the taste and taste of coffee, reaching about 190 degrees, and the conversion between endothermic and exothermic heat will occur again.

Of course, high temperature cracking is still occurring continuously, coffee beans change from brown to dark brown, and gradually enter the stage of re-baking.

(3) cooling Quenching

Coffee must be cooled immediately after roasting, quickly stop the high temperature cracking and lock the flavor, otherwise the high temperature inside the beans will continue to work and will burn off the aromatic substances.