Coffee Post Harvest Handling and processing in Kenya
Kenya grows the Arabica coffee species almost exclusively, which is processed by the wet method. Small-scale farmers produce the majority of the coffee. These farmers have formed co-operatives, which have put up pulping units referred to as Factories. These co-operatives have management committees that oversee the running of the Factories. Coffee is pulped and dried as parchment coffee in these factories. The dried parchment is stored temporarily before being transported to centrally located companies for hulling. The hulling companies are privately owned and hull the coffee for the farmers at a fee.
Coffee harvesting in Kenya is done by selective picking of the ripe berries. This is a labour intensive exercise and involves most of the members of a family and hired labour. Transportation to the Factories is by Ox-drawn carts, pick-up vehicles, and sometimes lorries. This is done immediately after harvesting.
The cherry is sorted out before pulping. This helps to remove the immature, diseased, insect damaged and dry berries as well as the leaves, twigs and other foreign matter. The sorted out berries are processed by the dry method.
Pulping is the mechanical removal of the pulp from the cherry to have parchment coffee. After pulping, the coffee is graded into three grades 1,2 and lights. This is done by density and size of the coffee. Parchment 1 is conveyed to the fermentation tanks while grade 2 and lights are further processed again through another smaller pulper called a re-passer.
i) Biochemical removal: Fermentation
Fermentation allows the mucilage layer on the parchment to be washed off easily. Completion of fermentation is determined by washing a bit of the parchment with clean water and then feeling the coffee with the hand. A gritty feel is an indication of the completion of fermentation. This stage takes 1 to 4 days depending on the prevailing weather conditions, faster on warm days and slow on cold days.
ii) Chemical Removal
Several chemical products are used for removal of the mucilage, mainly lime, which precipitates the pectins in the form of insoluble pectates, which are then easily removed by washing. Alkaline carbonates have also been used. This method is not common in Kenya.
Soaking is a complete immersion of the parchment under water. Studies in Kenya have shown that soaking of coffee parchment after fermentation for about 12 hours improves the coffee quality both in colour and taste. The parchment is thoroughly washed to remove the degraded mucilage and acids completely before soaking.
Final Washing and grading
After fermentation and soaking, the parchment coffee is thoroughly washed with clean water to remove any dirt or remains of mucilage or sugars. Final washing is done in concrete channels by pushing the parchment with wooden paddles against a stream of water. The washing channels are painted like the fermentation tanks with acid resistant black paint. The paint allows heat retention during fermentation and reduces friction between the coffee and the concrete surfaces during washing.
During final washing, the coffee is graded again by weight into different grades.
Freshly pulped coffee has a moisture content (mc) of about 55%, which has to be reduced by drying to 11%. This is the ideal level of moisture content required for proper storage, hulling and roasting. In Kenya, sun drying is predominantly used and mainly by the co-operatives and the coffee is spread on wire mesh tables for several days (normally about 14 days), until fully dry. When it rains, the coffee is covered by a polythene sheets to avoid re-wetting. Some big commercial estates use mechanical drying.
The following are the stages of parchment drying that are observed:
Skin Drying (55 - 45% mc)
This stage involves the removal of surface water and that between the parchment and the bean. The parchment is spread on layers not exceeding 0.5 inches on wire mesh tables and turned frequently to encourage rapid evaporation and at the same time it is fully exposed to the sun. This stage is normally completed on the same day of final washing. While stirring the parchment to ensure uniform drying, discoloured and broken beans are sorted.
This stage of drying can be mechanised.
White Drying Stage (44-35% mc)
At this stage, the parchment is white and it is easy to sort out the defective beans. Drying at this stage is made slow and controlled, and during very hot days, the coffee is covered during the hottest part of the day, (from 10.30 a.m. to 3.00 p.m.) in order to avoid cracking of the parchment cover. This stage can be mechanised with well controlled temperatures to avoid cracking of the parchment.
Soft Black Stage (35 -25 % mc)
At this stage the parchment attains is final black colour. In Kenya, it is recommended to only sun dry in this stage, for the coffee is said to be photosensitive and the sun light makes the coffee to acquire some preferred quality characteristics. The coffee is fully exposed to the sunlight for a period of 48 -50 hours. Mechanical drying is discouraged at this stage.
Hard Black Stage ( 25 -12 % mc)
At this stage the parchment is hard dark in colour and can be done rapidly without any loss of quality.
Fully Dry and Conditioning(12 -11 % mc)
This is done in ventilated stores or bins in order to even out the moisture of the coffee. At this moisture content, the coffee can be stored in well controlled environment without any effect on quality.
Storage of the coffee at the co-operative's stores is normally for a short while before delivery for hulling. In Kenya, this is done in good constructed stores, which allow good air circulation. The coffee is put in sacks and stacked on wooden palettes 0.5m above ground level and 0.5m away from the walls. Maximum care is taken to make sure that the coffee does not absorb any moisture. This storage is done for a maximum of 6 months.
Hulling plants and equipment are expensive and involve sophisticated technology, which the co-operatives can not offer. Private commercial coffee hulling companies that are centrally located have been started and hull the farmers' coffee at a fee. Some private coffee estates have their own hulling plants.
Dry Method of Coffee Processing
In Kenya this method is applied to Arabica coffee which is sorted out from the good cherry. The coffee is dried to attain the required moisture content of 11% and then is stored. It is later hulled where the dry pulp and parchment are removed in a single operation.
Liberalisation of the coffee industry in Kenya has affected coffee farming in several ways. The Government pull out in the controls in management of farmer's co-operatives has led to splits of the giant co-operative into smaller units. This has improved the management of the co-operatives and the payment speed to farmers. Smaller co-operatives require less management overheads and the farmers receive better prices for their crop. Introduction of privately owned hulling plants allows the farmers to choose and has brought competition among the hulling companies and reduced hulling losses and charges. Originally only one government controlled hulling company "Kenya Planters Co-operative Union (KPCU)", was licensed to hull most of the coffee grown in the country with an exception of large private coffee estates which have their own hulling facilities.
Currently farmers and the hulling companies are calling for the liberalisation of coffee marketing which has remained under the Coffee Board of Kenya (CBK). All Kenyan coffee is marketed through the Kenya Coffee Auction, which is fully owned by CBK. Liberalisation of the coffee marketing by licensing other marketing agents other than CBK will allow competition, which is good for the growth of the industry.