top of page

Green Bean Moisture and Its Impact on Coffee Quality

The moisture content of green coffee beans is one of the crucial factors in producing quality coffee. It directly affects the flavor of the coffee, and the roasting process, and can even impact the price that producers can command. Let's delve deeper into the significance of this factor for coffee roasters and producers in today's article.


What is the standard moisture content?

Moisture content is a measurement of the water or vapor present in a substance or environment, and it's the same for coffee. Although when you look at or gently touch green coffee beans (coffee beans that haven't been roasted), they may seem quite dry, in reality, they still contain a certain amount of water inside the beans. That's why when we measure the moisture content of coffee beans, it still shows a value. You can refer to the image above for reference.

The moisture content of coffee beans decreases during the drying process. Mature coffee cherries have a moisture content of about 45-55% after harvesting, and after processing and drying, the coffee beans are stored and ground when they reach a moisture content of around 10-12% (a moisture level of 10-12% is considered safe and preserves the best quality and flavor of green coffee beans according to the standards of SCA and CQI).

If you're curious about the SCA and CQI organizations, you can learn more by reading this article:


Controlling the quality of coffee during the drying process?

Coffee cherries tend to ripen unevenly, so there will be multiple stages of drying. In most specialty coffee farms, coffee is harvested in several rounds using the selective picking method (picking only ripe cherries). This means that during harvesting and processing, the coffee cannot be dried together on the same drying rack, as it would result in varying moisture levels for each batch of coffee, making it difficult for the processing facility to control the uniformity of moisture content across the batches.

Therefore, it is crucial for processing facilities to label each batch of coffee and monitor the moisture content to avoid mixing between different coffee batches, as the moisture content of the coffee is related to controlling the quality of uniformity and the flavor of the batches during roasting when the green coffee beans arrive at the roasting facility.

There are various methods for drying coffee, such as using drying racks, mechanical dryers, patios, and tarps.

In perfect climate conditions, the drying racks allow better air circulation and rotation of coffee beans. Furthermore, this can help prevent fermentation and mold.

However, mechanical dryers are also a good option for regions with unfavorable drying conditions, such as frequent rain or high humidity, as long as the drying temperature is controlled, not exceeding 40°C for parchment coffee and 45°C for natural coffee.

Regardless of the drying method used, moisture content testing is an essential part of this process.


What are the potential risks when green beans are too moist?

As we mentioned above, coffee with a moisture content above 12.5% is not acceptable. Coffee that is harvested while still too moist can lead to several serious issues:

  1. Mold and Fungus: High moisture content provides favorable conditions for the growth of mold and fungus. These patches of mold on the coffee not only compromise its quality but also affect the flavor. Coffee beans contaminated with mold often have unpleasant odors and flavors.

  2. Spoilage: Moist coffee beans can spoil faster. This reduces the shelf life and diminishes the quality of the coffee over time.

  3. Difficult Roasting: Moist coffee requires a longer roasting time. This can result in uneven roasting, affecting the final flavor.

  4. Brand Devaluation: Moist coffee doesn't always command a good brand value. Customers may be disappointed with the quality, leading to damage to the brand's reputation.

  5. Financial Loss: Producers may lose money due to selling batches of coffee that do not meet moisture requirements or contracts that aren't renewed.

In simple terms, if coffee is too moist, it will create numerous quality issues for both the coffee producers and the consumers. Therefore, it's best to ensure that coffee is stored in a dry and well-ventilated environment to avoid these undesirable effects.


The dangers of green coffee beans being too dry?

In the opposite case, when green coffee beans are over-dried, both producers and consumers encounter difficulties:

  1. Weight Loss and Reduced Revenue: Over-dried coffee loses a significant amount of moisture, making the coffee beans lighter. Consequently, coffee production decreases, leading to a reduction in revenue.

  2. Impact on Coffee Quality: Coffee that is over-dried can lose flavor and freshness, affecting the overall quality of the coffee. For example, at 9% moisture content, you can expect the coffee to lose aroma. If the moisture level drops below 8%, roasted coffee beans will have very little flavor or almost no flavor at all. This can significantly diminish the value of the coffee.

  3. Difficult Roasting: Moisture content is crucial during the roasting process. Since water conducts heat, the moisture in the coffee beans provides a path for heat to reach the core of the bean. When coffee beans are over-dried, the outer layer of the bean roasts too quickly while the inside remains relatively unchanged, resulting in an unpleasant grassy flavor.

Over-dried coffee not only impacts the quality of the coffee but also has negative effects on the business outcomes and trade relationships of farmers. Maintaining proper moisture levels during the processing and storage of coffee is essential to ensure their interests and the sustainability of the coffee industry.

The moisture content of coffee plays a crucial role in its flavor and quality. Maintaining stable moisture levels in production and storage is extremely important. For coffee makers, maintaining this stability is a significant challenge, but it leads to producing the finest coffee beans, creating the most unique flavors enjoyed by coffee lovers worldwide.

At iO Coffee, we value and preserve the precious aspects of the processes that result in coffee beans with distinct and unique qualities. You can also enjoy these offerings here:

247 views0 comments


bottom of page