Introduction of coffee roasting method and process what is the secret of coffee roasting? coffee roasting curve skills

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Coffee roasting accounts for 80% of the importance of a good cup of coffee, and since the taste of coffee has been lost during roasting, how to grasp the "best coffee baking time" is the key. The so-called best time does not have an objective value, but depends on the flavor you like. The deeper the roast, the better the aftertaste; the shallower the roast, the more aroma the coffee itself retains. The most feared situation is that each kind of coffee beans are roasted into a flavor and lose their characteristics.

That is, each kind of coffee beans are roasted separately, this method and commonly used mixed roasting can highlight the distinct characteristics of coffee beans, but mixed baking is convenient to buy time, and the taste of all kinds of beans is also more integrated.

In his coffee roasting book Roasting Craft, South Korean Liu Chengquan uses a chart to divide the coffee roasting process (Roasting Process) into several important stages: adding beans, Turning Point, boiling, Yellow Point, Mena reaction, caramelization, first explosion (maybe into second explosion), lower beans, cooling.

Even if each baker develops personalized baking curves and techniques according to his or her own habits and preferences

STEP 1: from imported beans to T.Point

Bean feeding is the initial stage of baking. after putting the beans in a preheated drum, the drum temperature will drop immediately until the drum temperature and the bean temperature reach balance. Generally speaking, it is appropriate to reach T.Point (temperature recovery point) within 120 seconds. If the temperature of the T.Point is too low, the time to reach the first explosion will be too long. On the contrary, the T.Point temperature is too high, the time to reach the first explosion will be too short. Therefore, it is necessary to calculate the ROR to determine the temperature of the bean.

STEP 2: from T.Point to Yellow

After T.Point, raw beans enter the endothermic stage. 70% of the bean weight is made up of insoluble (Insoluble) cellulose (Cellulose). In order to transfer heat to the inside of the bean, the water conductivity is used. If the bean water content is low, the time to reach the Yellow stage will be shorter, on the contrary, if the bean water content is high, the time to reach Yellow will be longer.

At the bean temperature of 100. C as the starting point, water changes from Evaporation to Vaporization, and the vapor pressure and temperature inside the bean rise. At this time, the bean tissue undergoes vitrification (Vitrification), begins to expand, destroys chlorophyll and enters Yellow.

STEP 3: from Mena reaction (Maillard Reaction) to 154. C

The baking temperature reached 154. At C, the temperature and pressure inside and outside the beans are at about the same stage, the sugar components are decomposed into reducing sugar (Reducing sugar) by adding water, and then combine with amino acids (Amino acids) to produce Melanoidine-like (Melanoidine) and volatile organic compounds (VOCs), which is the Mena reaction. Through this process, coffee beans will produce flavor changes.

STEP 4: from caramelization (Caramelization) 160.C to 200.C

At this stage, beans are caramelized by thermal decomposition, which begins to reduce sweetness and transform into a very complex flavor (Aroma). At the same time, due to the increase of CO2 pressure and vapor pressure, the beans began to produce a fever reaction.

STEP 5: from the first explosion to 194Murray 5.C

When the vapor pressure and CO2 pressure inside the bean accumulate, the first burst (1st Crack) occurs. The "blow holes" produced at this time becomes the outlet for the discharge of Flavor compounds inside the bean. At this stage, the beans are completely converted to a febrile reaction.

The first explosion is the most critical Point in the whole baking process. From then on, the flavor of the affiliated Sugar Browning (Nutty, Caramelly, Chocolaty) will appear, and most bakers will estimate the "development rate" (DTR. Development Time Ratio).

STEP 6: from the second explosion to 220. C

The CO2 pressure accumulated due to thermal combustion is released outward, and the beans burst again, which is called the "second explosion". At this stage, the cell structure of beans begins to be destroyed, and the interior begins to be coked or carbonized (Carbon). From then on, the flavors attached to Dry Distillation (Resin, Spice, Carbon) will appear and produce obvious bitterness.

STEP 7: from bean production to cooling (Cooling)

Although the beans begin to cool immediately after they are produced, the temperature of the beans will not drop immediately. Because the temperature inside the bean can be maintained at a high temperature for a period of time, the high temperature maintained by the bean itself may change the roasting degree of the coffee and may lead to the volatilization of the aromatic flavor. therefore, rapid cooling is a very important step to maintain the flavor.