Creating and maintaining quality in a cup of specialty coffee requires several finely-tuned value additions along the supply chain. According to a study published by the African Crop Science Society in 2007, the quality of green coffee is 40% pre-harvest and harvest processes, 40% post-harvest processes, and 20% export handling measures. Read on to discover the factors that have the great influence on the quality of green coffee from farm to port.
This is where the commitment and investment of the farmers is paramount. First farmers must harvest the best quality cherries. Several factors contribute to the quality of cherries including soil characteristics, pest prevalence and harvesting methods.
Pre-harvest & harvest
According to FAO, coffee requires a free draining soil with a minimum depth of one metre. Coffee will not tolerate water logging or ‘wet feet’. Coffee can be grown on many different soil types, but the ideal is a fertile, volcanic red earth or a deep, sandy loam. Coffee prefers a soil with pH of 5 to 6. Low pH will limit crop performance by limiting the availability of key nutrients to coffee plants.
Overuse of fertilisers can lower the quality of a coffee. According to a study by Bonga University in southern Ethiopia, too much nitrogen in the soil will result in lighter weight and more bitter beans.
Pest and disease management
Effective pest and disease management is crucial to produce high quality coffee. Pests and diseases cause cherries to deteriorate and coffee plants will not be able to produce the desired quality or yield. Pests and diseases can be managed by careful hygiene, pruning, field monitoring, as well as the application of pesticides and use of natural alternatives like encouraging predators of the pests.
Hand picking coffee leads to much higher quality than mechanical harvesting. It results in greater consistency in ripeness, a higher volume of ripe cherries, and fewer defective cherries.
It is possible to sort the coffee post harvest when using mechanical harvesters, however this will result in a larger range of qualities, and therefore lower yield of high quality coffee.
In many countries the post-harvest process is managed by the farmer themselves in a small “beneficio” or washing station on their property. In most parts of Africa however, the post-harvest process is managed by separate washing stations who purchase cherry from hundreds, sometimes thousands, of farmers in their area. We refer to the people who manage post-harvest processing as “Producers” regardless of whether they grew the coffee themselves or purchased cherries from other farmers.
Post harvest process can be natural or washed. The washed method involves removing the cherry skin and mucilage, before drying the beans. The natural method involves drying cherries directly after harvest on mats, patios or raised beds.
Quality washed processes
The major factors that affect parchment quality are fermentation, drying and storage. Post-harvest stage is the responsibility of washing stations.
During the fermentation process, the producer must monitor the temperature of the water, and the duration of the fermentation. In our experience in Ethiopia, the ideal fermentation duration is 24-48 hours. Fermentation duration is inversely proportional with temperature; the higher the temperature, the faster the fermentation.
After fermentation, parchment is dried on drying beds. The volume of parchment on a bed must be laid out in a specific depth, ideally 2cms in our experience.
Once drying is done, parchment will be stored. Stored parchment must be handled with great care. Storing the coffee too long or in humid conditions will increase the moisture content of parchment, which decreases its quality.
Quality natural processes
The natural method of post-harvest processing is less complicated than the washed process but more dependent on environmental conditions and time. Cherries must be spread over a thin layer on well ventilated drying beds and regularly raked to maintain uniform exposure to the sun. Drying duration must be monitored carefully to ensure it doesn’t happen too quickly and that coffees are dried to ideal moisture levels. When cherries are overdried, they become brittle and break down during hulling. Under dried cherries will be exposed to fungus and bacteria. The ideal drying duration ranges from 10 days to three weeks, depending on the ambient temperature.
Parchment coffee must be transported to a central warehouse, milled, packed and shipped. Exporters are usually responsible for this stage of the value chain.
Dry milling is the process of converting parchment into green coffee. During dry milling, grading and sorting must be done well to ensure absence of defects. Tropiq Ethiopia’s staff conduct a physical evaluation of the greens, test for moisture and water activity, and roast the milled coffee for cupping in our lab.
Once the milled coffee has been tested and approved, the next step is packaging. It is important to use the right packaging material to preserve the quality of the coffee during transportation. Our coffees are always packed in 60kg jute sacks lined with Grain Pro bags. Once the coffee is packed, the Tropiq Ethiopia team takes a pre-shipment sample to test and cup.
Before the coffee hits the water, it will be loaded into containers on trucks that will transport it to the port in Djibouti. Tropiq’s team examines containers and oversees loading to ensure the consistency of the quality during shipment.
Tropiq’s role in maintaining quality
The Tropiq Ethiopia team works with stakeholders on all three stages to deliver on the promise of high quality green coffee to our customers. We work with farmers to observe and advise on pre-harvest and harvest management. We visit washing stations and dry mills regularly to investigate the processes and follow up on our selected lots. We also maintain good working relationships with washing stations and exporters so we can give advice and request certain requirements that fit our quality standards.