Coffee roasting skills basic knowledge, curve adjustment, flavor mastery

The flavor of coffee is largely determined by the qualification of raw beans, and roasting is only a way to show the characteristics of coffee beans.

After roasting, various ingredients of raw coffee beans have undergone chemical changes, thus forming the flavor of coffee. In other words, what kind of chemical change occurs, to what extent, and to what extent to stop the reaction from continuing-these are the main points of baking.

The chemical reactions of various components in raw beans will be affected by both temperature and time. Over time, how the temperature of the coffee bean rises, to how many degrees Celsius (that is, the degree of coloring)-these two points basically determine the flavor of the coffee. Although everyone feels that baking is difficult, the principle of baking is actually very simple. Baking is a continuous reaction of "how many degrees Celsius does the temperature of coffee beans change in a minute?" This continuous reaction needs to be controlled by recording the temperature changing every minute (the temperature shown on the machine is not the temperature of the coffee beans, but the temperature of the baking room, from which the temperature of the coffee beans can be inferred). We record these figures on a chart, using the horizontal axis to represent the time and the vertical axis to represent the temperature, which is called the "coffee baking curve".

Even in the same producing area, if the batches (processing units) of raw coffee beans are different, the proportion of ingredients that make up the baking color will be different, and the coloring methods will be different. Therefore, in order to maintain a stable baking level, the same batch of raw beans should be used as much as possible, and the coloring method of the new batch should be confirmed when replacing the new batch. However, the same batch of raw coffee beans, there will also be a big difference in quality or placed for a long time, resulting in changes in quality. In order to ensure the stability of the baking level of the same batch of secondary beans, we must first ensure the consistency of baking methods. Not only the input of raw beans should be fixed, but also the firepower or air valve should not be adjusted at will. In addition, the baking quantity can be divided into several batches. The first batch can be roasted deeper, and the second batch should be roasted shallower, mixing and blending the coffee beans made twice, so that the uneven baking degree offsets each other.

When baking, it is very important to record the heating mode of coffee beans at all times and to master the "usual" state. If the temperature is different from the usual "popping", it should be corrected according to this difference (for example, if the temperature is 2 ℃ higher than the usual "popping", then the temperature when you stop baking is 2 ℃ higher than usual), and if the baking time is longer (shorter) than usual, the baking temperature should be lowered (higher) accordingly.

Only by mastering the "usual" baking status, can we make micro-adjustments in time to ensure high-precision baking quality. If the temperature changes obviously, you can also turn down the firepower or open the gas valve; if the temperature changes slowly, you can increase the firepower or close the gas valve.

So, how to test the degree of baking? If the quality requirements are very strict, it is necessary to set the color specifications of roasted coffee beans in advance. In order to check whether they meet the specifications, a color meter (colorimeter) can be used to measure color, freshness, brightness and other indicators. The weight loss of coffee beans (the weight change before and after baking) can also be used as a criterion for the degree of baking. If you lose much less weight than usual, it may be because the baking is too deep.

This article is reproduced from the author of the brief book: Royal West Point Culture.