Coffee roaster training and terminology how can coffee roasting produce oil coffee beans roast degree

An explosion

At the end of the endothermic reaction stage and the first burst, the heat protection reaction is carried out immediately.

The sound produced by the expansion effect produced by the preheating of raw beans during the first burst, the sound and time of bursting will vary with the variety, density and vitality of the endothermic reaction stage. Under the condition of high temperature baking, direct fire baking will occur in 7 minutes, while semi-hot air or full hot air will occur in about 9 minutes.

An explosion represents the official beginning of the chemical reaction of raw beans. Generally speaking, we take continuous bursting as the starting point. Before that, there will be a single burst sound (when the tissue of raw beans changes, some raw beans will burst). Under this condition, please do not take a single burst sound as the basis. After a single burst sound, the continuous burst sound will begin soon, and this point in time can easily be used as the basis for the confirmation of an explosion.

After the explosion starts, you will smell a sour smell. With the passage of time, the sound of bursting becomes louder and louder, and you can feel that the sour taste is getting stronger and stronger, and the strength of this sour taste will vary from place to place. For example, raw beans at high altitude taste more sour than those at low altitude, and sun beans taste more sour than washed beans.

When the sour taste irritates to the depths of the nasal cavity, please reduce the firepower. If the firepower is not reduced and continues, the temperature will show a black curve and continue to rise; while after the nasal cavity is stimulated by sour taste, confirm and adjust the firepower, the temperature rise in the furnace will gradually slow down and show a blue curve.

The second explosion (the fire is not reduced in the first explosion)

As I just said, if the firepower is not adjusted when the explosion is dense, the temperature in the furnace will rise. If you use fresh raw beans with a water content of more than 10% for baking, the finished product with less firepower during the second explosion will have a brighter reddish brown than the original bean without firepower adjustment; if you use a direct-fire baking machine, you may have to adjust the firepower up at the same time or just before the second explosion. Because if the direct fire is not hot enough, it will cause the second explosion later, or the overall baking time will be prolonged. This situation has a bad effect on the taste and flavor of coffee, causing strong bitterness and its bitterness will stay in the mouth for a long time, resulting in a large loss of aroma.

The second explosion (reducing fire when the first explosion occurs)

After an explosion, the blue curve after firepower adjustment is reduced. The blue curve is relatively flat, on the whole, there is no downward trend, but shows a slowly upward trend. In case of a downward trend, it means that if the firepower is too strong, the beans baked in this case are darker, called dark black, bitter and aftertaste, and will become insipid and tasteless coffee.