The roasting process of coffee is the direct heating of the roast.

Simply put, baking is the direct heating of baked goods. Unlike cooking, baking does not require oil, water, salt or sugar. Just put the green coffee beans in a heat-resistant container and heat them over a fire. While heating, stir the coffee beans so that each bean is evenly heated. When we reach the desired level, stop heating. The whole process is actually a bit like barbecue, except that the roasted things are coffee beans.

The process of coffee from green beans to ripe beans is quite dramatic. Without roasting, coffee would not have the familiar aroma, complex taste buds, and certainly not as popular as it is now! Coffee beans smell green before they are roasted, and some dried beans even smell fermented! The process of roasting raw beans into ripe beans is called caramelization. In the caramelization process, the sugars, fats, proteins and amino acids in coffee beans... And so on and so forth began to interact and combine, and the result was to go from more than 200 substances in the beginning to more than 800 substances in the end, such as the familiar coffee aroma, which is the melanin-like taste produced after caramelization.

The first explosion: coffee beans generally contain about 10% moisture, when roasting begins, this moisture will be the first thing to run out of the coffee beans, so the initial stage is dehydration. As the temperature gradually rises, the gas and water inside the coffee bean will start to give pressure to the cell wall because it wants to escape. When the pressure accumulates to 20~25 atmospheres, the cell wall will break through. This is when you will hear the explosion sound. We call this stage the 'first explosion'. The temperature at this time is about 190~200 degrees Celsius. Because each baking is in batches, some beans will burst earlier to facilitate cracking; some will be later, so the sound must be sporadic at first, then gradually dense, and finally gradually sparse and even end (it is recommended to record the start and end time). At this time, the color of the coffee beans is not the initial khaki color, but a slightly lighter coffee color, the general coffee beans will be roasted at least to this extent before the pot, we call this degree of roasting 'light roast'.

The second explosion: the temperature at the end of the first explosion will be about 205 degrees, and then as the heating continues, the temperature continues to rise, the color of the coffee beans will gradually become darker, and when the temperature reaches 230 degrees, the coffee beans will also emit a cracking sound, which is the second explosion. The sound of the second explosion is small and high frequency, which is not the same as the first explosion. At the same time, the film on the surface of the coffee beans will fall off. The color of the coffee beans entering the second explosion will be darker, and the surface will begin to appear oily.

Deep Roast: After the second explosion, it will enter the deep roast level. At this time, the coffee beans will become oily black and will emit a lot of smoke. If the house is equipped with smoke detectors, it is best to turn off the alarm first, so as not to make the whole building know that you are roasting coffee! At this point, the temperature usually does not exceed 240 degrees Celsius. If you want to do further deep roasting, you have to raise the temperature to more than 240 degrees Celsius. At this time, the surface of the coffee beans will become almost black and appear very greasy. This is probably the limit of the roasting depth of coffee beans. In the roasting, it is guaranteed that the coffee beans will burn up and become authentic freshly roasted coffee beans.