April 26


The Different Methods of Curing Robusta Coffee Beans

By Hanson Cheng

April 26, 2023

In this article, readers will gain a comprehensive understanding of Robusta coffee beans, from their characteristics and geographical distribution to their preparation, curing, and drying methods. The article also delves into proper storage and handling practices, quality assessment and grading systems, and the export and distribution process, adhering to international standards and regulations. By the end of the article, readers will have a clear understanding of the entire Robusta coffee production process and how to maintain its quality from farm to market.

Overview of Robusta Coffee Beans

Characteristics of Robusta Beans

Robusta coffee beans are one of the two main species of coffee plants, the other being Arabica. Known scientifically as Coffea canephora, Robusta beans are more bitter and contain a higher amount of caffeine compared to Arabica beans. These beans are characterized by a more robust and stronger flavor with a distinct earthy and nutty taste, which some people even describe as having hints of chocolate and rubber.

In terms of appearance, Robusta beans are smaller and rounder compared to Arabica beans. They also have a straight crease down the middle, while the Arabica beans have a curved crease. In terms of cultivation, Robusta plants are hardier and more resistant to diseases, which makes them easier and more affordable to grow. This is one of the reasons why Robusta beans are generally cheaper than Arabica beans.

Geographical Distribution

Robusta coffee plants are primarily grown in the Eastern Hemisphere, with the majority of production occurring in Africa, Asia, and the Middle East. The largest producers of Robusta coffee beans are Vietnam, Brazil, Indonesia, and Uganda.

These plants thrive in low-altitude, warm climates with temperatures ranging between 70-90°F (24-32°C). They can grow at elevations as low as sea level and up to 2,000 meters above sea level, but the optimal elevation for their growth is between 400-800 meters. Robusta plants can tolerate a wider range of environmental conditions than Arabica plants, which contributes to their widespread cultivation.

Preparation of Robusta Coffee Beans for Curing

Selecting and Harvesting Coffee Cherries

The first step in the preparation of Robusta coffee beans for curing is selecting and harvesting the coffee cherries. Coffee cherries are typically harvested when they reach a deep red or purple color, which indicates that they have reached peak ripeness.

There are two main methods for cherry harvesting: hand-picking and mechanical harvesting. Hand-picking involves manual labor, where workers selectively pick ripe cherries from the coffee plants. This method is more time-consuming and labor-intensive, but it allows for better quality control as unripe or overripe cherries can be left on the plant.

Mechanical harvesting, on the other hand, uses machines to strip all cherries from the plants, which is faster and more efficient but may lead to a mix of ripe and unripe cherries.

Sorting and Cleaning Process

After harvesting, the coffee cherries go through a sorting and cleaning process to remove any debris, leaves, or defective cherries. This can be done manually by hand or using various machines like air classifiers, which segregate the cherries based on their size and density. In some cases, the cherries are also soaked in water; the ripe ones will sink while the unripe or damaged ones will float, making it easier to separate them.

Curing Methods for Robusta Coffee Beans

Natural/Dry Process

The natural or dry process is the oldest and simplest method of curing coffee beans. It involves spreading the harvested coffee cherries out on a large surface (usually raised beds or concrete patios) and allowing them to dry in the sun. The cherries are regularly turned to ensure even drying, and this process can take several weeks to complete.

Once the cherries have dried and reached the desired moisture content (usually around 10-12%), they are hulled to separate the beans from the dried fruit and parchment. The beans are then sorted and graded based on size and quality.

Advantages and Disadvantages

The dry process is a more eco-friendly method as it requires less water compared to the wet process. It also generally produces beans with a sweeter and fruitier flavor profile. However, this method is labor-intensive and requires ideal weather conditions, with low humidity and ample sunlight, to ensure proper drying.

Wet Processing Method

The wet processing method, also known as the washed method, involves removing the pulp from the cherries immediately after harvesting. This is done using a depulping machine, which separates the beans from the fruit. The beans are then soaked in water for 12-48 hours to ferment and remove any remaining mucilage.

After fermentation, the beans are washed thoroughly to remove any remaining residue before being spread out to dry either in the sun or using mechanical dryers. Once the beans have reached the desired moisture content, they are hulled, sorted, and graded like in the dry process.

Advantages and Disadvantages

The wet process produces beans with a cleaner and brighter flavor profile and generally yields a higher quality end product. The fermentation step helps develop desirable flavors in the beans. However, this method requires a lot of water, which can be problematic in regions with water scarcity.

Choosing the Right Method

Both dry and wet processing methods have their own advantages and disadvantages when it comes to curing Robusta coffee beans. The choice of which method to use largely depends on the desired flavor profile, available resources (water, labor, and equipment), and the environmental conditions in the region where the beans are processed.

Drying Methods for Cured Robusta Coffee Beans

Sun Drying

Sun drying is the traditional and most commonly used method for drying coffee beans. It is an energy-efficient and cost-effective method that involves spreading the cured coffee beans in a thin layer on drying beds, trays, or patios. The beans are exposed to direct sunlight, with a gradual decrease of moisture content through evaporation.

During the drying process, it is essential to turn over the beans periodically to ensure even drying and avoiding mildew growth or fermentation. The process generally takes 10 to 15 days to complete and results in a moisture content of 11-12%.

Sun drying does have limitations; It can be weather-dependent and relies on consistent sunlight and low humidity during the drying period. Additionally, uneven drying can result in lower quality and inconsistent flavor.

Mechanical Drying

Mechanical drying involves the use of specialized equipment such as mechanical driers, drying cabinets, or silos. These machines control the temperature, airflow, and humidity levels to provide a more consistent and efficient drying process. This method is particularly useful in regions with high humidity or unpredictable weather conditions since it can operate independently of the external environment.

Mechanical drying usually takes between 24 and 48 hours to complete, depending on the equipment used, and reduces the beans’ moisture content to 11-12%. However, the higher operating costs, energy consumption, and capital investment required for equipment can make this method less feasible for small-scale farmers.

Combination of Sun and Mechanical Drying

Combining sun and mechanical drying methods can provide the benefits of both techniques while mitigating their weaknesses. The beans can be initially sun-dried to reduce overall moisture content, followed by mechanical drying to achieve the desired level of dryness and consistency more rapidly.

Using a combination of both methods can result in higher quality coffee, lower instances of defects, and better control over the drying process. It can also save on energy costs compared to solely mechanical drying.

Monitoring Moisture Content During Drying Process

During the drying process, it is essential to monitor the moisture content of the coffee beans to achieve optimal results. Excessively dry beans may become brittle and lose flavor, whereas insufficiently dried beans can be susceptible to mold growth and spoilage during storage. The ideal moisture content for cured Robusta coffee beans is 11-12%.

Monitoring can be done through visual inspection or the use of electronic moisture meters. Electronic moisture meters provide accurate, real-time measurements of the beans’ moisture content, allowing for better control and adjustments during the drying process.

Storing and Handling Cured Robusta Coffee Beans

Proper Storage Conditions

Proper storage conditions are crucial to maintain the quality of cured Robusta coffee beans. The beans should be stored in a cool, dry area with consistent temperature and relative humidity levels. Exposing the beans to moisture, excessive heat, or rapid temperature fluctuations can negatively impact the quality and shelf life of the beans.

Ideal storage facilities should have proper ventilation and be designed to minimize the risk of mold growth, pest infestations, and cross-contamination from other products.

Handling Cured Coffee Beans

During handling and transportation, it is essential to ensure that the coffee beans do not come into contact with moisture or any contaminants. Care must be taken not to damage the beans as they move between different stages of the supply chain. Damaged beans can result in reduced quality, increased defects, or spoilage.

Proper practices include using clean, food-grade storage containers or bags, avoiding exposure to water, and preventing contact with any sources of contamination such as chemicals or strong odors.

Preventing Mold and Pest Infestation

Mold and pest infestations can be detrimental to the quality and safety of cured Robusta coffee beans. Preventive measures must be implemented to minimize the risk of such issues, including:

  • Regular inspection and maintenance of storage facilities
  • Hygienic handling of beans during transportation and processing
  • Adequate ventilation and humidity control in storage areas
  • Using pest-resistant storage containers or bags
  • Implementing pest control practices and monitoring systems

Quality Assessment and Grading of Cured Robusta Coffee Beans

Physical Inspection

The physical inspection involves examining the beans for various quality parameters, including bean size and consistency, color, appearance, and the presence of defects or imperfections.

Bean size and consistency are important indicators of the beans’ uniformity and processing quality. Larger beans are generally considered to result in better flavor and aroma due to their increased surface area. However, all beans should be of similar size and shape to maintain a uniform roast and overall quality.

The color of the coffee beans can also provide insight into the processing and drying methods used. Beans that are too dark or have a spotted appearance may indicate improper drying or over-fermentation.

Defects and imperfections, such as broken beans, insect damage, or mold growth, will reduce the quality and value of the coffee beans. A thorough inspection should be conducted to ensure these issues are kept to a minimum and not passed on to consumers.

Tasting and Cupping Tests

Tasting and cupping tests are essential tools for assessing the flavor and aroma profile of cured Robusta coffee beans. These tests are generally performed by trained coffee professionals using standardized methodologies, such as the Specialty Coffee Association’s cupping protocol.

Cupping involves the evaluation of various aspects of coffee quality, including fragrance, aroma, flavor, body, acidity, and aftertaste. The results of the cupping tests can provide valuable insights into the quality of the coffee beans and help identify any potential issues or areas of improvement in the processing and handling methods.

The drying, storage, and handling of cured Robusta coffee beans significantly impact the final product’s quality and value. Proper processes and quality control measures must be in place to ensure consistent, high-quality coffee that meets consumers’ expectations.

Export and Distribution of Cured Robusta Coffee Beans

Packaging for Export

The proper and effective packaging of cured Robusta coffee beans is crucial for maintaining the beans’ high quality and ensuring a successful exportation process. The packaging must protect the beans from potential contaminants, moisture, and external damages during transportation and storage.

One of the commonly used materials for packaging cured Robusta coffee beans is jute bags. Jute bags are made of natural, biodegradable fibers, which offer excellent breathability, allowing the beans to maintain their integrity and quality during transportation. Additionally, jute bags are relatively cost-effective and can be easily recycled or composted after use.

Another popular packaging option for cured Robusta coffee beans is GrainPro bags. GrainPro bags are made of polyethylene and provide a hermetic seal, preventing the entry of moisture, oxygen, and other contaminants. These bags are often used as liners inside jute bags, offering a double layer of protection to maintain the quality of the beans.

Vacuum packaging is another method used for exporting cured Robusta beans, especially for smaller shipments. This process involves removing air from the package and sealing it, preventing the beans from oxidizing, and maintaining their freshness for a longer time. However, vacuum packaging may not be suitable for larger shipments as it may require more space for shipping and storage.

When packaging cured Robusta coffee beans for export, it is essential to adhere to the specific importing country’s requirements for packaging materials, weight limits, labeling, and other regulations. Proper packaging ensures that the beans will arrive at their destination in prime condition and are well received by the global coffee market.

Adhering to International Coffee Standards and Regulations

To successfully export and distribute cured Robusta coffee beans, it is crucial to adhere to international coffee standards and regulations. Some of the significant organizations responsible for setting these standards include the International Coffee Organization (ICO) and the Specialty Coffee Association (SCA).

The ICO establishes minimum standards for coffee quality, grading, and labeling. Exporting countries must adhere to these rules to maintain a good reputation in the international coffee trade. The SCA also sets standards related to cupping scores, green coffee grading, water quality, and brewing methods. Understanding and complying with these standards will ensure quality and consistency, allowing the cured Robusta beans to compete in the global market effectively.

Some importing countries may have additional regulations regarding food safety, traceability, pesticide residues, and sustainability, among others. Exporters must familiarize themselves with these requirements to avoid potential issues during the import process, such as shipment delays, fines, or rejections.

Another critical aspect of adhering to international coffee standards and regulations is working with reliable and experienced logistics partners who understand the intricacies of coffee bean transportation, handling, and customs clearance. This will ensure a seamless and efficient exportation process.

Understanding Market Trends and Demands

To successfully export and distribute cured Robusta coffee beans, understanding the dynamics of the global coffee market and evolving consumer preferences is essential. This knowledge will allow exporters to position and differentiate their offerings better, targeting the right customers and markets.

For instance, the demand for certified sustainable and traceable coffee has been on the rise as consumers become more environmentally and socially conscious. Exporters of cured Robusta beans can capitalize on this trend by obtaining certifications such as Fair Trade, Rainforest Alliance, or UTZ. These certifications can offer additional value to the beans, potentially leading to increased demand and better prices.

There has also been a growing interest in specialty Robusta beans, which are known for their unique flavors and lower acidity compared to Arabica beans. By focusing on distinct, high-quality Robusta beans, exporters can cater to the growing demand from artisanal roasters, cafes, and consumers.

Similarly, understanding the preferences of different regions and cultures can help in targeting the right markets for cured Robusta coffee beans. Some countries may prefer a more mild or dark roast, while others might be interested in unique flavor profiles and attributes.

To achieve success in exporting and distributing cured Robusta coffee beans, it is crucial to focus on proper packaging, adherence to international standards and regulations, and understanding market trends and demands. By doing so, exporters can ensure that their beans are of the highest quality, appealing to a wider consumer base, and are well-received in the global market.

Curing Robusta Coffee Beans – FAQs

1. What is the significance of curing Robusta coffee beans?

Curing Robusta coffee beans is crucial for enhancing their flavor, aroma, and color. This post-harvest processing method removes the outer fruit layer, allowing the beans to dry correctly, stabilize flavors, and reduce acidity. Proper curing is essential for obtaining a desirable taste profile and enjoying a delicious cup of Robusta coffee.

2. How do the methods of curing Robusta coffee beans differ from Arabica beans?

The curing methods for Robusta coffee beans may slightly differ from those for Arabica beans, mainly due to variations in bean sizes, densities, and sugar contents. However, the most common methods—natural (sun-drying), honey, and washed—apply to both. The optimal curing approach for Robusta beans depends on local climate, labor availability, and desired flavor profiles.

3. What is the natural (sun-drying) method for curing Robusta coffee beans?

The natural or sun-drying method involves spreading freshly harvested Robusta coffee cherries on a flat surface, such as a patio or raised beds, exposed to direct sunlight. The cherries are regularly turned or raked to ensure even drying for typically 12-24 days. This approach imparts fruity flavors and heavy body to the Robusta beans.

4. Can you explain the honey process in curing Robusta coffee beans?

The honey process entails the partial removal of the outer fruit layer before drying Robusta coffee beans. The beans, still coated with some mucilage (honey-like substance), are spread out to dry, usually on raised beds, for about 15-25 days. This process offers unique taste profiles, varying sweetness levels, and increased body to the final coffee.

5. What does the washed method involve in the curing of Robusta coffee beans?

The washed method involves fully removing the outer fruit layer and any remaining mucilage from the harvested Robusta coffee beans using water and fermentation tanks. Once cleaned, the beans are spread on a drying surface for about 10-15 days. This method highlights the inherent flavors and acidity while maintaining a clean and balanced cup profile.

6. How does the curing process of Robusta coffee beans affect their quality?

The curing process of Robusta coffee beans influences their final taste, aroma, and body characteristics. Proper curing ensures optimal moisture levels, flavor development, and bean uniformity. An ideal curing method balances efficiency and desired attributes, resulting in high-quality Robusta beans that offer a delightful coffee drinking experience.

Hanson Cheng

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