COFFEE

 COFFEE PRODUCTION

Coffee plant is known to have originated in Africa. Coffea arabica known as Arabica and Coffea canephora also called Robusta are the two major species due to their huge commercial value. Arabica is widely grown, accounting for more than 60% of the total world coffee production because of its good cup quality. Robusta on the other hand, is majorly used for instant and blended coffee. Other varieties include Liberica and Excelsca. 

Ripening coffee cherries on a coffee tree. 📷Kelvin Karuga

Coffee is primarily grown in the Coffee Belt. The regions within the belt provides perfect climate conditions and elevation for successful cultivation of coffee plants. The Coffee Belt lies between the Tropics of Cancer and Capricorn.

Coffee growing involves planting coffee seeds in nurseries then transplanting them to farms. The coffee plants are either shade-grown common in Guatemala, Ethiopia or sun-grown common in Brazil, Colombia. Shade-grown coffee is grown on plantations that have shade trees or modified forests. Shade trees examples are timber trees or even fruit trees. Sun-grown coffee is grown in open fields with direct sunlight.  

After transplanting, the coffee plant will go through rapid leaf, stem and root development. This is the vegetative growth stage which is followed by the flowering stage where blooming of white fragrant flowers occur.

Coffee tree blossoms with white flowers. 📷Kelvin Karuga

In the end of flowering stage, the flowers fall leaving tiny round nubs also called carpels which later develops into cherries. The coffee cherry starts as small green berry and gradually ripen with cherries going through various color stages until they are ready for harvesting.

Ripe coffee cherries on a coffee tree branch. 📷Kelvin Karuga

COFFEE HARVESTING

There are three methods of coffee harvesting namely; Selective, Strip and Mechanical.

Selective harvesting            

Harvesters hand picks only cherries that are perfectly ripe and leaves overripe and unripe cherries. The overripe will eventually fall off on their own while the unripe will be picked in the coming weeks as soon as they ripen. This harvesting method guarantees very high quality cherries due to the attention to detail. 

Strip harvesting

Harvesters pulls everything from the branch of a coffee plant by hand, taking out ripe, unripe and overripe cherries altogether along with leaves and twigs. Separation is done after harvesting. 

This method can also be done using a smaller handheld machine called "Derricadeiras". The harvester places the machine on the coffee branches and turns it on leading to vibrations that shake the cherries loose.

Mechanical harvesting

This is strip harvesting on a large scale. Mechanical harvesters are used to knock off the coffee fruits off the coffee trees. This is suitable for larger coffee plantations where land is relatively flat.

COFFEE PROCESSING

This is the transformation of coffee cherries to green coffee beans in readiness for roasting. It involves removal of coffee seed from the pulp, mucilage and parchment. There are three major coffee processing methods namely; Natural, Washed and Honey. Every processing method brings out unique flavor profile.

 

A coffee processing plant in a coffee farm. 📷Kelvin Karuga

Natural Process

This is also known as the dry process. Whole coffee cherries are spread out in patios or raised drying beds. They are left to dry while constantly turning them to achieve uniform drying and to prevent spoilage from growth of fungus and molds. This takes several weeks until the coffee attains correct moisture content.

Sun drying coffee on the coffee drying beds. 📷Kelvin Karuga

Washed Process

This is also known as the wet process. Whole coffee cherries are initially placed in water for water separation. This step assists in sorting whereby, the unripe and defective cherries will float while the ripe ones will sink. Outer skin and pulp is then removed using a machine called depulper. Any remaining pulp and mucilage will then be eliminated through the fermentation. Finally, the beans are washed repeatedly to ensure there is no mucilage left then transferred to raised beds for drying. They are constantly turned to ensure uniform drying and to prevent spoilage.

Coffee soaking tanks. 📷Kelvin Karuga

Honey Process

This is also known as the pulped natural process. The name 'honey' from the honey process is derived from the sticky mucilage which appears and feels like honey as it dries. In this method, the outer skin of the cherry and pulp is removed leaving some of the mucilage. There are different types of honey processes which are determined by the amount of mucilage left. They include; white honey, yellow honey, red honey and black honey with white having most mucilage removed to black having the least. The beans are then moved to drying beds where they will be periodically turned to ensure even drying and prevent spoilage. Drying can also be done using mechanical dryers.

Other processing methods include Carbonic Maceration whereby whole coffee cherries are fermented in sealed tanks with carbon dioxide and Anaerobic Fermentation whereby cherries or beans are placed in sealed containers without oxygen to ferment.

 HULLING

This process is also known as milling or husking. This process is done after drying and it involves the removal of parchment layer from the dried coffee beans, leaving behind only silver skin.  

  

CLEANING, SORTING AND GRADING

Green coffee beans are sorted to remove debris for example stones and twigs as a measure to ensure high quality. Grading is also done at this stage. It involves screening to separate the beans in sizes, visual inspection for any defects and cupping to evaluate their aroma, flavor, body and acidity.

STORAGE AND TRANSPORTATION

Storage of green coffee beans and transportation to roasters is widely done in Hessian sacks which are made from natural fibers like hemp, sisal or jute. Other methods include Hermetic bags  and Vacuum packing.    

Green coffee beans stored in hessian sacks at a roastery. 📷David Omondi

ROASTING

This is the transformation of the physical and chemical properties of the green coffee beans by exposure to heat. 

 

A coffee roaster in a modern roastery. 📷Erick Juma

Roasting leads to color changes, increment in volume and enhanced flavors. This is the final stage to consumption. Roast profiles for instance Light, Medium and Dark are achieved based on varying temperature and duration of roasting. Once the desired roast profile is achieved , roasting stops and the coffee is released from the roasting drum into the cooling sieve. After cooling, the coffee passes through a destoner, whereby any stone that might be in the coffee is removed. Sorting to remove quakers is also done at this point. This can be done manually or by using optical sorter also known as color sorter.

Quakers appear pale compared to the perfectly roasted beans in the batch.  📷Erick Juma

Quakers are mainly immature green beans that do not fully roast ending up in a lighter color compared to fully developed cherries. Its important to pick cherries that are fully ripe among other factors to avoid quakers. Effects of quakers in a cup of coffee include bitter, dry sensation that leaves unpleasant taste in the mouth.

A roast batch exhibiting uniform color. 📷Erick Juma

  

The roasted coffee is allowed to degas then packaged. The packaged coffee may be allowed more time to degas before use.

PACKAGING

After roasting, whole beans or freshly ground coffee is usually packaged in valve sealed bags while instant coffee is packaged in sealed airtight containers.

Freshly roasted coffee beans packaged in a valve sealed bag. 📷Erick Juma