How to understand the coffee roasting curve? senior barista

Introduction to coffee roasting

However, as a roaster, the choice of coffee roasting degree should not only start from the roaster's personal interests and hobbies, but should focus on the needs of the audience, so there is a reason for shallow baking and a reason for deep roasting. There is no difference between the two. If your guests pursue the taste and the local characteristics of the coffee origin, then light baking can make your customers more clearly aware of what they need. On the contrary, if your guests prefer round, mellow and sweet coffee, then medium or even deep roasting is more appropriate. But Uncle Dou wants to say a word for the roasters who roast coffee deeply. Many roasters with light roasting style think that when coffee is roasted deeply, there is no other flavor except bitterness in the coffee, and the flavor of coffee is lost in deep roasting. This statement is not objective. A roaster who is good at deep roasting coffee, not only is there no burning smell in his coffee, but the guests can also feel the flavor of the coffee. In other words, the coffee will only be roasted to the black out of oil, the smell of smoke is extremely strong, he is not a baker, but charcoal burning.

With the continuous absorption of heat, more and more volatile gases (mainly water vapor) accumulate in the coffee beans, which causes the pressure inside the beans to far exceed the external atmospheric pressure, even reaching 25 atmospheric pressure (2533 kPa). The internal pressure is so high that it is like a small bomb that is finally enough to tear the structure of the raw coffee beans. This critical moment is called First Crack.

In a sense, as long as there is an explosion of coffee beans, they can be cooled, ground and drunk, but it is still a very shallow baking degree, which may not be the best baking degree we want. Next, we should pay close attention to the stage of roasting, observe the color of coffee raw beans by sampling, smell the aroma changes of coffee raw beans, find the best baking degree, and then cool it decisively. We know that the ingredients in raw coffee beans are in the following order: sugars, moisture, fatty substances, proteins, acids, minerals, alkaloids (such as caffeine) and other volatile aromatic substances. The content of these substances essentially determines the flavor of a cup of coffee drink with the increase of the surface temperature of coffee beans and the decrease of the temperature difference between bean surface and core. A considerable proportion of the water has been dissipated in the process. If you look at the sample in the sampling rod at this time, you will find that a light yellowish brown begins to appear, and then look down and smell it, and the original pure smell of hay is replaced by a hint of sweetness, which means that the time has come for chemical reaction to dominate baking. At this time, we should give enough heat supply so that a large number of chemical reactions that need to absorb heat and produce charming flavor can be carried out smoothly. It is precisely because of the addition of a large number of endothermic chemical reactions that the temperature rise slope of coffee beans we have observed begins to slow down.