2/53 Group 51, Quarter 3, Buu Hoa Ward, Bien Hoa City, Dong Nai Province, Viet Nam
Contact now: 0936 198 938
English VietNam 

How moisture of the green coffee affects the roasting process

By: Admin | 27/10/2020 15:32

How moisture of the green coffee affects the roasting process

How moisture of the green coffee affects the roasting process
One of the factors that play an important role in the roasting process is the moisture content of the coffee bean. In this article, we will focus on this factor and explain its effects.

Moisture in green coffee
Unprocessed ripe coffee beans should have a moisture content of 45–55% after picking. The subsequent processing and drying will reduce its moisture content by 10–12%.

In general, we recommend that storage conditions are 40 to 70% relative humidity with ambient temperatures between 40 and 70 ° F / 21 ° C. On top of that, make sure your coffee is packed well, using a zipper-packed bag. Depending on how green coffee is packaged and stored, humidity can vary due to climate.

So, what is the problem with moisture content of green coffee beans? The moisture content of coffee beans is partly free, in the cell structure and partly in the carbohydrate molecular structure of coffee. During roasting, the free moisture will evaporate before and at a later stage, the bound moisture will evaporate.

Three-stage roasting cycle
In this picture, it is clear which stage of the coffee bean goes through the roasting process.

# Phase 1
We can summarize roasting as a three-stage cycle, starting with the drying phase. During this period the moisture content of coffee drops to about 2%. The first stage of the roasting process is to remove as much water from the coffee bean so that the flavor can be developed in a later stage. Free moisture also plays a role in heat transfer during roasting. As soon as the bean is exposed to heat, its moisture conducts this heat throughout the bean. When the temperature inside the seed reaches 212 ° F / 100 ° C, the free moisture begins to evaporate.

# Phase 2
During the second stage, from 280 ° F / 137 ° C to 350 ° F / 176 ° C, the beans develop their specific aroma and taste through chemical changes caused by the so-called "Maillard response". By the end of the second stage almost all of the free moisture has evaporated. The length of the second stage depends on the roasting profile selected and in particular on the amount of heat applied to the coffee.

# Phase 3
During the third stage of roasting, the caramelization causes chemical changes that cause the development of a prized and distinct coffee aroma and flavor. O Tesla's roasting technology allows the roasting operator to navigate through these 3 essential stages consistently and with the optimum level of control.

Moisture affects roasting time
Coffee with a moisture content less than 10% has a reduced free moisture content and will tend to roast much faster, especially in the early stages. In this case, the roaster operator needs to change the roasting configuration by charging the beans at a lower heat level and maintaining a lower energy supply (less BTU) during the first roasting stage. Roasting is the key to finding that perfection.

Coffee with high humidity (fresh coffee can have moisture content in excess of 14%) often requires the roaster operator to include a pre-drying phase before starting the first stage of the process.

How to dry first
During pre-drying, the roaster should maintain a drum temperature of 300 ° F / 148 ° C. This removes excess free moisture.