To get that green bean that gives coffee its distinctive flavours and nuances, this is it – processing
From Bean to Brew: Making the Perfect Cup of Coffee
By Waikwa Maina and Smart Farmer Team
Processing is a whole world of its own.
While the coffee industry predominantly focuses on quantity and quality at the farm level, the journey from cherry picking to the final stages of bean grading before the magic of roasting begins, is the most crucial.
This is where every step, every touch, every smell, every hour… infuses the final cup with its distinctive character and taste.
Coffee processing refers to the methods used to transform the harvested cherries into green coffee beans that can be roasted and brewed. It significantly influences the flavour of the coffee.
These steps start right from harvesting to storage, where quality checks are critical.
Picking the cherries (harvesting)
It starts with the harvest. To maintain quality and grade, growers are advised to selectively harvest fully red-ripe beans, avoiding semi-mature or semi-ripe beans, as well as those that have fallen on the ground.
Mr Peter Chege, an agronomist at the Resources Oriented Development Initiatives (RODI) Kenya, likens the cherries to human food, stressing that once they drop from the tree, they absorb the soil taste irreversibly, compromising quality to the cup.
“At picking, the farmer must avoid semi-mature and semi-ripe beans and those that have aborted to the ground. The beans, after harvest, must be treated as human food. Each farmer should treat the cherry as they treat any harvest meant for family consumption,” says Mr Chege.
He spoke during an interview with Smart Farmer.
The agronomist warns about the delicateness of the coffee yield, pointing out that a minor error can ruin the entire harvest.
“No error is reversible in coffee. It’s a very sensitive yield that can pick up a very faint smell or dirt capable of ruining the entire party,” he adds.
The harvesting team’s general cleanliness’ is paramount, down to the containers and bags that are used. Cherries can absorb the smells and tastes from unclean equipment.
Mr Chege also cautions against the smoking of cigarettes on the farms and in factories, as the smell can permeate the cherries, leaving an undesirable trace in the final product.
At the checkpoint: Sorting
In our (Smart Farmer) conversations with coffee production experts and farmers, sorting emerges as one of the constant themes, stressing its pivotal role in ensuring the pristine quality of every bean. Even the slightest error in the grading can cause irreparable damage to the cherry’s quality, leading to the loss of entire batches at the factory or co-operative society level.
“There is no shortcut in coffee farming. Everything must be done according to the coffee calendar and with strict adherence to after-harvest processing systems. Sorting, and counter-checking and checking again is critical,” says Mr John Kirathe, the general manager of Giakanja Cooperative Society in Nyeri County.
After harvesting, the beans are delivered to the factories where sorting is done before the grower is cleared to proceed with the weighing. At this stage, which is also a quality control check, the farmer or workers sort the semi-ripe, the wounded or ripe beans with blackish spots, attributed to the coffee berry disease (CBD), and the dry beans commonly known as “mbuni”.
Overnight storage: Mr Chege warns against the common mistake of overnight storage of beans by farmers before delivery to the factory. This initiates fermentation, irreversibly affecting the beans’ taste and smell.
“The other mistake that farmers make is harvesting and storing overnight at home, compromising the quality of the coffee due to fermentation.”
Once sorted, it is time to take your coffee through a chosen processing method, before it is turned into green beans.
Processing Methods
There are several methods of processing coffee, each with its unique characteristics. The three primary methods are washed (wet), natural (dry), and honey processing.
These methods contribute to the diversity of coffee flavours, and variations exist within each method based on factors such as climate, altitude, and specific techniques employed by individual coffee producers.
Today, as farmers in Kenya begin to find their own markets, they are getting into experimentation with new ways of processing, such as anaerobic fermentation, the naturals, and carbonic maceration.
The coffees from these new methods are often pricier than conventional methods. However, experts advise against using these methods without having a direct market. Here are the various processes:
- Washed (wet)
This is the most common method.
- Pulping: After sorting the cherries, the outer skin is removed, leaving the beans covered in mucilage. This is known as pulping. During the pulping, beans are also separated in terms of grades to get parchment 1, parchment 2, and lights.
- Fermentation: They are then directed into different fermentation tanks and fermented in water to remove the mucilage. This can take 12 to 72 hours.
- Washing: The beans are washed to remove any remaining mucilage.
- Cleanliness: Producers must adhere to strict cleanliness to avoid mixing the beans with dirt or introducing smells that could affect the taste.
- Drying: The washed beans are dried in the sun or mechanically until they reach an optimal moisture level.
Flavour profile: Washed coffees often have a cleaner, brighter acidity and a more pronounced clarity of flavour.
- Honey
Pulping: Like the pulped natural process, the outer skin is removed, but some or all of the mucilage is intentionally left on the beans.
- Drying: The beans with mucilage are dried in the sun or using mechanical dryers. The amount of mucilage left can vary (e.g., white honey, yellow honey, red honey).
- Milling: After drying, the beans are milled to remove the remaining mucilage.
Flavour Profile: Honey process coffees exhibit a balance between the cleanliness of washed coffees and the fruity sweetness of natural process coffees. The flavour can vary based on the amount of mucilage left on the beans.
