Popular science | changes in coffee bean roasting

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Coffee fruits are harvested and processed to become raw coffee beans, and raw coffee beans must be roasted before they become common coffee beans on the market. After roasting at high temperatures, they will emit aroma and darken color, while roasting of raw coffee beans will produce the following phenomena:

(1) weight loss: raw coffee beans are roasted at more than 200 ℃, and the moisture in the beans evaporates with the baking degree, and the moisture content decreases from about 13% to 1%. Due to the reduction of water content, the weight will also be reduced by 12% and 21%, and the deeper the roasting degree is, the lighter the weight is.

(2) Volume expansion: when water evaporates, the pores of coffee beans increase, and the volume of coffee beans increases. With different roasting degrees, the volume of coffee beans increases by about 60%.

(3) exhaust: the process by which raw coffee beans release carbon dioxide (CO2) during roasting. Exhaust makes oxygen (O2) not easy to invade, that is, oxidation destroys the flavor of coffee, but the exhaust speed slows down after baking, and oxygen molecules are easy to attach to the bean table, which deteriorates the flavor of coffee, so coffee beans must be drunk as soon as possible after contact with air.

(4) Color: with the heating time and temperature, the color of coffee beans will change from golden yellow to light brown, and then the oil will become tea-brown, and a large amount of oil will be black and oily.

(5) change the composition: after roasting, the composition of coffee beans will change with the absorption of heat, and the aroma of coffee will be enhanced with different roasting degree and chemical changes, forming different aromas of coffee.