Professional coffee roasting | what is "explosion"? Is "explosion" important for coffee roasting?

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I wonder if you have any habit or experience of cooking? When food is cooked in a pot, it often produces aroma, heat, and even sound. When we can "explode" some food, we will describe it as very stale. In previous articles, we mentioned that the principles of coffee roasting and cooking are very similar. Therefore, when the coffee is roasted, there will also be the so-called aroma, heat and sound. At the most intense moment, it is time to "explode".

What is meant by "an explosion"?

The so-called "explosion" refers to the obvious and strong sound of coffee beans in the machine when coffee is roasted, a bit like the sound of making popcorn or burning firewood. From a cooking point of view, it shows a lot of "arrogance". We know that coffee roasting is actually about the physical and chemical changes of coffee beans. When raw beans are put into the dryer, there is a physical change: dehydration. In this process, the coffee bean is in the endothermic stage, and the rising temperature turns the water of the coffee bean into steam, which in turn reduces the water content, which is called dehydration. When the coffee bean absorbs heat and the pressure caused by the evaporation of water in the bean is greater than the strength of the coffee bean itself, the cell wall of the coffee bean will burst because it cannot withstand the pressure of the heart expansion, and the coffee bean will make a burst sound and release heat and sound energy. This is the emergence of "one explosion".

Is "explosion" important for coffee roasting?

I would say that "burst" is the sound that the bean baker is looking for during the baking process. In the process of "explosion", in addition to the physical reaction, it also represents a chemical change in coffee beans.

If you only boast about some proper chemical terms, it may make it more difficult for people to understand the principle. Why don't you stay close and take coffee tasting as an example.

For those who like coffee, some will like the fruit acid, some will like the sweet taste of caramel, while others will like the coffee with heavy tea and floral flavor. Why does a cup of coffee have so many flavors? Isn't coffee bitter and sour? In fact, those tastes are the flavor of tasting coffee. The formation of flavor is largely attributed to the growing environment of coffee beans, the influence of the weather and the treatment methods used by hard-working coffee farmers. And does the bean baker have no responsibility for flavor building? Of course not. A good bean baker should understand that he has an important responsibility, that is, to check the baking corner, present those flavors with different baking degrees, and make the best use of them. Just like cooking, if the best ingredients are given to a bad cook, the best taste will be destroyed by him.

In the "explosion" stage, the molecules in coffee beans interact with heat, releasing different flavor compounds (that is, flower, fruit, etc.) and browning (that's why coffee beans are brown). At this time, it is also a time when the development of coffee beans has changed greatly, it may only come out one second earlier or one second later, and its flavor can also be very different. Therefore, when an explosion occurs, the baker is particularly important for the control of firepower and time, and any adjustment can definitely affect the flavor of a bean. Therefore, an explosion is not only a reminder, but also an indispensable element in the development of flavor in coffee bean roasting.

If you have a chance to try coffee roasting, remember to pay attention to the sound like burning firewood. This is an explosion!