Three baking processes: drying, high temperature decomposition and cooling

Newly imported coffee beans usually contain about 12% moisture, and when the coffee beans are roasted at a high baking temperature from 500 to 800 degrees Fahrenheit, when the coffee beans heat up, the water evaporates. Most of the moisture is released in the first few minutes of the baking process, although the baking time in the United States is usually about 15 minutes, which may be 5 minutes or as long as an hour. After 8 minutes, the temperature of the beans will rise to 300 degrees Fahrenheit and the beans will lose green, turn yellow and begin to turn brown. Between 260 and 370 degrees Fahrenheit, between 11 and 12 minutes, more water will slowly dissipate, coffee beans reach 390 degrees Fahrenheit, coffee becomes light brown. At 14 minutes, the temperature of the beans reaches 410 degrees Fahrenheit and the color changes to a moderate brown color. At 16 minutes, the temperature of the beans reaches 440 degrees Fahrenheit, and the color turns dark brown, which is almost equivalent to French baking. If you bake one more minute, the temperature will exceed 450 degrees Fahrenheit and turn into Italian and dark brown beans at 465 degrees Fahrenheit and 20% weightlessness.

In fact, the time control, temperature and color changes will be based on the method of fried beans, cycle period, the type of beans, the original moisture content, the speed of heating. And so on, rather than a universal description of the whole process. In all cases of baking, what really matters is that a large amount of heat is released from coffee beans at 400 degrees Fahrenheit, which is called high temperature decomposition or chemical decomposition of caramel. Sivetz invented the method of temperature and time measurement at the end of 1974. in June 1975, the A.S.I.C conference in Hamburg demonstrated that heat release is measurable and directly related to the baking quality of raw beans, that is, beans grown at the highest latitudes and the most fragrant beans release the most heat, the beans at lower latitudes are gently washed, releasing less heat, and the beans at the lowest latitudes are not released.

High temperature decomposition produces acetaldehyde and other attractive coffee aromas, which appear and maintain for a short time. High temperature decomposition determines how long the coffee taste lasts. That is, how deep we are allowed to roast coffee, some of the chemicals volatilized by coffee under high temperature decomposition are carbon dioxide, acetaldehyde, ketone, ether, acetic acid, methanol, vegetable oil, water vapor, glycerin. The particularly bad smell after baking is sour, and spicy and choking. The coffee roasting process usually takes 7 minutes in a continuous roaster and 12 to 15 minutes in a 4-bag roaster. When the baking time is more than half an hour, the coffee beans will have a light baking flavor rather than a strong aroma. The baking process is usually accompanied by a crisp explosion and lampblack formed mostly by blue water vapor. As soon as you get the ideal coffee color, the coffee beans must be poured out of the extremely hot fire immediately, and use the surrounding air and spray to cool it quickly and correctly. When you cool the coffee beans, most of the water will evaporate, and even if you spray a small amount of water mist, almost no water will be absorbed by the coffee beans. Cooled beans will stop the decomposition of high temperature. If you maintain the high temperature of the beans, the aroma will be much lower.