What happens during coffee roasting? coffee bean roasting temperature and time coffee roasting taste

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Roasted coffee transforms the chemical and physical properties of raw coffee beans into roasted coffee products. The roasting process causes raw beans to expand and change their color, taste, smell and density, resulting in the special flavor of coffee. Unroasted coffee beans and roasted coffee beans contain similar acidity, protein and caffeine, but lack their good taste. The process needs to be hot enough to accelerate Maillard's reaction with other chemical reactions that add flavor.

As raw coffee beans are much more stable than roasted coffee beans, the roasting process tends to take place near the consumer market. This reduces the delivery time of roasted coffee beans and maximizes the shelf life of coffee beans. The vast majority of coffee beans are roasted commercially on a large scale, but some coffee drinkers bake their own beans in order to accurately control their freshness and taste.

Different roasting methods will affect the flavor, aroma and taste of the final coffee, because chemical changes will occur at different time points during roasting.

But regardless of the baking method, baking is mainly divided into three stages: dehydration, Maynard (caramelization) reaction, and flavor development. These terms actually describe the different stages of chemical and physical changes.

1. dehydration

The dehydration process occurs at the temperature recovery point, which is when you put the raw beans in the baking machine, the heat inside the machine will drop before rising again, and the point at which the temperature begins to rise is called the temperature recovery point. During the dehydration stage, the water in the raw beans will begin to evaporate and the pressure will begin to form inside the beans.

two。 Maynard reaction

When the coffee beans begin to turn brown, the Maynard reaction begins, which happens when heated to about 150 °C. This process produces a lot of gases, including carbon dioxide, water vapor, volatile gases and so on. When the internal pressure is large enough to break through the cell wall, it expands, which is called the first explosion.

Flavor development will also occur at the same time in Maynard reaction, in addition to beans color change, but also affect the final coffee flavor.

3. Flavor development period

When baked to an explosion, baking changes from an endothermic reaction (absorbing heat from the drum) to an exothermic reaction (beans release heat). At this stage, the physical changes will continue, the pores on the bean surface will continue to increase, the oil will continue to move from the core to the surface, and the color will continue to darken. Many chemical reactions also take place at this stage.