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Monitoring Moisture Levels in Coffee Production

Posted on August 22, 2019

The process of growing, harvesting and drying good quality coffee is one that requires a great deal of care and attention. A long list of variables can affect the end product, including temperature, soil quality, air quality and moisture.

Moisture is arguably one of the most critical factors in this case, as it dictates to such an extent the quality of the coffee. An imbalance in one direction or the other can result in the coffee becoming spoiled before it even reaches the roaster.


After growing, provided the process has been conducted properly, coffee beans should reach an optimum level of moisture. This is the point at which they should be picked to produce the best coffee possible.

This optimum level varies from variety to variety and from region to region. However, picking the beans at the correct time can help to avoid issues such as discolouration. When they become discoloured, they lose their naturally green tint and develop a musty white shade.


Drying of coffee beans is conducted in a variety of ways, all resulting in different flavour profiles. During the drying process, the moisture content of the beans is dropped from around 60% to closer to 11 – 12%.

Monitoring moisture levels at this stage is vital as beans that are allowed to sit too long during the drying can become mouldy and spoiled. Or, on the other end of the scale, they can become overly dry and ruined.

A study conducted in Kenya determined that there are six stages of the drying process:

  1. Skin Drying. Moisture: 55-45%
  2. White Stage Drying. Moisture: 44-33%
  3. Soft Black Stage. Moisture: 32-22%
  4. Medium Black Stage. Moisture: 21-16%
  5. Hard Black Stage. Moisture: 15-12%
  6. Fully Dry Coffee. Moisture: 15-12%

Effective moisture monitoring is vital at all six stages to preserve the condition of the coffee.

Shipping and Roasting

Once dried and packed, coffee is then shipped to the roastery to complete the final stage of its production. During the shipping process, the beans are exposed to a wide variety of fluctuating temperatures and humidity levels.

These constant changes can result in the degradation of the carefully prepared product. Therefore, moisture monitoring at this stage is just as vital as at every other stage. Coffee roasteries will treat beans differently based upon relative moisture levels.

They will apply varying time scales and temperatures in order to make the most of the beans and their drying process prior to this. As a result, roasteries must be keenly aware of the moisture content of the beans they roast.

At all stages of coffee production, moisture levels must be closely monitored and acted upon, in order to produce the desired end result. Improper care can lead to beans that are spoiled or produce a poor-quality coffee.

In order to ensure levels are properly monitored, the correct range of equipment must be used, in this case; moisture sensors and transmitters.

Omni Sensors and Transmitters is an industry-leading supplier of the very latest in sensor and transmitter technology. To learn more about our range of moisture sensors and transmitters, click here.

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