Coffee roasting A physical change in the roasting stage of coffee at roasting temperature and time.

Professional coffee knowledge exchange more coffee bean information please follow the coffee workshop (Wechat official account cafe_style)

The importance of physical structure

The layered structure of coffee beans has a great influence on the flavor we want. Without a specific physical structure, the chemical reactions essential to flavor and aroma will not take place.

Grinding raw beans into powder and placing them at the same temperature as when baking will not produce the flavor compounds we need. Intact coffee beans are necessary to produce chemical reactions. The complete structure can control and reflect the baking environment on the right premise and can react with each other in the right order.

A dramatic change in baking

Coffee beans are dense and compact seeds, but once they start roasting, they change their original state. Let's take a look at what happens when roasting:

A change in color

Perhaps the most obvious change during baking is the color. Before baking, fresh raw coffee beans appear blue-green and then turn brown due to melanoid production. These are polymers formed when sugars and amino acids combine under heating. In the baking process, part of the silver skin will also fall off, silver skin is the closest to the coffee bean's outer paper material.

Bean bakers and consumers will use color as the standard to define the quality of coffee beans and baking results.

Change of moisture content and quality

The moisture content of raw coffee beans after drying process is about 10-12%, but after baking, the moisture content will be reduced to about 2.5%. In addition to the water that already exists in raw beans, additional water is produced through chemical reactions, but this evaporates during baking.

The loss of water and the conversion of some dry substances into gas are the reasons for the decrease of the overall quality of raw beans after baking. On average, coffee beans lose 12-20% of their weight before and after baking. Bakers often record the weightlessness ratio to determine which batches of raw beans may require additional monitoring in terms of quality.

Different baking curves will affect the time of dehydration, baking at different time points, the change of water activity may represent the difference of chemical reaction, which may affect the final baking curve.