[coffee roasting] Fire throttle control of roaster (4) | Coffee workshop

For professional baristas, please follow the coffee workshop (Wechat official account cafe_style)

During the dehydration process, when the raw bean changed to yellow, a series of chemical reactions such as Maillard reaction, which were very important for the production and transformation of coffee flavor substances, began to take place actively. However, at this time, it is not said that the dehydration of raw beans stopped, but the roasting process began to change from the removal of moisture from raw beans to the formation and decomposition of chemicals in raw beans, and the flavor of coffee began to form.

Taiwan Pegasus coffee bean roaster 801N/1kg semi-hot air

For beans with different hardness, size and treatment, the adjustment of firepower throttle will be different at this time. After the raw beans begin to turn yellow, the body of the beans will become a little softer, and the sound of stirring the raw beans in the boiler will be lower than when they were first put into the pot. Raw beans are no longer as strong as they were when they were first baked, and a high temperature rise may burn the bean watch. At the same time, the occurrence of chemical reactions, the production of flavor substances need to absorb heat, so this stage must have enough firepower to provide sufficient capacity for the reaction to proceed.

Therefore, for some hard beans, larger beans can not reduce firepower or even add a little firepower to provide enough ability to maintain the chemical reaction. For some beans that are small and easy to be penetrated by firepower or soft beans can be lowered a little bit or. Generally speaking, keep the temperature rise at 9-12 degrees, and the temperature rise per minute is slightly lower than the previous minute. If the temperature rise is higher than the previous minute, there is a good chance that the beans will be burned, resulting in a bitter taste.

Taiwan Pegasus coffee bean roaster 801N/1kg semi-hot air

After turning yellow, the throttle also needs to be slightly opened, and even some roasters and baking conditions can allow the introduction of a large amount of hot air at this stage to promote the full reaction of the material. The silver skin attached to the raw bean will fall off during the second half of the dehydration stage to the time when the raw bean turns yellow. if the silver skin is not extracted from the boiler in time, the residual silver skin will begin to carbonize and produce particles attached to the coffee bean surface when the temperature reaches a certain degree, leaving a bitter taste and dirty taste for the coffee. Therefore, after turning yellow, we should open the big throttle to remove the silver skin. generally, the sun beans will have more silver skin and will need a larger throttle. The wide opening of the throttle can also produce stronger thermal convection in the boiler.

Compared with the heat transfer of coffee beans in direct contact with the boiler, the heat convection heating of raw beans will be more uniform, so that the coffee flavor has a better development, will make the coffee more clear and transparent. However, too large throttle will quickly take away the heat, which may cause the temperature rise of the boiler to drop too sharply or even lose temperature, so that there is not enough capacity to promote the reaction. Therefore, it should be adjusted reasonably.