Harvesting and Processing Of Cacao Fruits
How long does it take for a cocoa pod to be ripe? After successful pollination of the flowers the fruits containing the beans, known as cocoa pods, take 5 to 6 months to ripen.
Harvesting of Cacao Pods
Pods containing cocoa beans grow from the trunk and branches of the cocoa tree. Harvesting involves removing ripe pods from the trees and opening them to extract the wet beans.
Pods are suitable for harvest for 3 to 4 weeks, after which time the beans begin to germinate. It is therefore necessary to harvest at regular intervals as the pods do not all ripen at the same time. The frequency of harvesting can have an effect on yield.
The pods are harvested manually by making a clean cut through the stalk with a well sharpened blade. For pods high on the tree, a pruning hook type of tool can be used with a handle on the end of a long pole.
By pushing or pulling according to the position of the fruit, the upper and lower blades of the tool enable the stalk to be cut cleanly without damaging the branch which bears it.
During harvesting it is important not to damage the flower cushionwhich will produce the flowers and fruits of subsequent harvests, and care must be taken not to damage the tree, which would make it easy for parasitic fungi to penetrate the tissues of the tree. The ripe pods are opened to remove the beans within a week to 10 days after harvesting.
Harvested Cocoapods,some depulped (right-handside)
In general the harvested pods are grouped together and split either in or at the edge of the plantation.
Sometimes the pods are transported to a fermentary before splitting. If the pods are opened in the planting areas the discarded husks can be distributed throughout the fields to return nutrients to the soil.
The best way of opening the pods is to use a wooden club which, if it strikes the central area of the pod, causes it to split into two;
Halves; it is then easy to remove by hand the beans. A cutting tool, such as a machete, is often used to split the pod though this can damage the beans.
Some machinery has been developed for pod opening but smallholders in general carry out the process manually.
After extraction from the pod, the beans undergo a fermentation and drying process before being bagged for delivery.
Fermentation Processes in Cocoa
Fermentation can be carried out in a variety of ways, but all methods depend on removing the beans from the pods and heaping them together to allow micro- organisms to develop and initiate the fermentation of the pulp surrounding the beans.
On smallholdings, fermentation is usually done in heaps of beans enclosed by plantain or banana leaves. Heaps can be used to ferment any quantity from about 25kg to 2,500kg of cocoa beans.
The fermentation usually lasts about five days and some farmers will mix the beans on the second or third day. Another smallholder method is to use baskets, lined and covered with leaves, to ferment the beans.
Similarly, holes or small depressions in the ground can be used but this makes no provision for the juices to drain away.
In plantations or fermentaries, fermentation is normally carried out in large wooden boxes that typically hold 1 to 2 tons of beans. The boxes must have provision for the liquefied pulp to drain away and for entry of air.
Boxes can measure 1m x 1m by 0.75m deep (3ft to 5ft across and be 3ft deep), but shallow levels –0.5m (10-20 inches) of beans are preferred to promote good aeration. The beans can be covered with banana leaves or sacking to conserve the heat generated during fermentation.
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Beans can be transferred from one box to another each day to ensure uniform fermentation and increase aeration. The boxes can be tiered to allow easy transfer of beans. Plantations usually ferment for a longer period than smallholders and 6 to 7 days is usual.
In some areas, where particularly acidic beans are produced, the beans are pressed prior to fermentation to reduce the amount of pulp and allow for better aeration of the beans and so reduce the acidity.
The fermentation process begins with the growth of micro-organisms. In particular, yeasts grow on the pulp surrounding the beans. Insects, such as the Drosophila melanogaster or vinegar-fly, are probably responsible for the transfer of micro- organisms to the heaps of beans.
The yeasts convert the sugars in the pulp surrounding the beans to ethanol. Bacteria then start to oxidize the ethanol to acetic acid and then to carbon dioxide and water, producing more heat and raising the temperature.
The pulp starts to break down and drain away during the second day. Lactic acid, which converts the alcohol to lactic acid in anaerobic conditions, is produced but, as the acetic acid more actively oxidizes the alcohol to acetic acid, conditions become more aerobic and halt the activity of lactic acid.
The temperature is raised to 40oC to 45oC during the first 48 hours of fermentation. In the remaining days, bacterial activity continues under increasing aeration conditions as the pulp drains away and the temperature is maintained.
The process of turning or mixing the beans increases aeration and, consequently, bacterial activity. The acetic acid and high temperatures kill the cocoa bean by the second day.
The death of the bean causes cell walls to break down and previously segregated substances to mix.
This allows complex chemical changes to take place in the bean such as enzyme activity, oxidation and the breakdown of proteins into amino acids. These chemical reactions cause the chocolate flavour and colour to develop.
The length of fermentation varies depending on the bean type, Forastero beans require about 5 days and Criollo beans 2-3 days.
Following fermentation the beans are dried. The oxidation reactions begun through fermentation continue during drying.
Roles of Yeasts in the Cocoa Fermentation Process
Cocoa pods are harvested and split open to release the beans. The beans are embedded in a pulp.
When the pods are broken, the beans and pulp are sterile but they become contaminated with a variety of microrganisms from the pods, labourers’ hands, insects, vessels used for transport, etc.
The pulp surrounding the beans undergoes a fermentation process which develops the colour and flavour of the beans. The initial anaerobic, low pH and high sugar conditions of the pulp favour yeast activity.
Some research has found 24 strains of yeast on fermenting cocoa, but research by Rombouts identified 16 species. The fermentation process begins with yeasts converting sugars in the pulp to alcohol and carbon dioxide.
Bacteria then start oxidising the alcohol into lactic acid and then, as conditions become more aerobic, acetic acid. This produces heat and raises the temperature in the first 24 hours. As the pulp breaks down and drains away, bacteria continue to be active until fermentation is complete.
The yeasts found during cocoa fermentation come from the surrounding environment, eg soil, trees etc.
The species most frequently found at this stage are the Saccharomyces spp (in particular S. cerevisiae, Candida krusei, Kloeckra apiculata, Pichia Fermentans, Hansenula anomola and Schizo-saccharomyces pombe).
Research by Hansen and Welty shows that yeasts multiply very rapidly during fermentation and are able to survive drying and storage. One can find up to 107 yeast/gram in stored beans.
Drying Cocoa Beans
Cocoa beans are dried after fermentation in order to reduce the moisture content from about 60% to about 7.5%. Drying must be carried out carefully to ensure that off-flavours are not developed.
Drying should take place slowly. If the beans are dried too quickly some of the chemical reactions started in the fermentation process are not allowed to complete their work and the beans are acidic with a bitter flavour.
However, if the drying is too slow, moulds and off-flavours can develop. Various research studies indicate that bean temperatures during drying should not exceed 65oC.
There are two methods for drying beans – sun drying and artificial drying.
For sun drying, the beans are spread out on mats, trays or on concrete floors in the sun. In some countries in the West Indies and South America drying takes place on wooden drying floors with moveable roofs.
The beans are normally turned or raked to ensure uniformity of drying and the beans need to be covered when it rains. Sun drying is used in countries where harvesting occurs in a dry period such as West Africa or the West Indies.
With adequate sunshine and little rainfall, sun drying may take about one week, but if the weather is dull or rainy it will take longer.
Artificial drying may be resorted to in countries where there is a lack of pronounced dry periods after harvesting and fermentation, such as Brazil, Ecuador and in South East Asia and sometimes in West Africa. Artificially dried beans can be of poor quality due to contamination from the smoke of fires or because the cocoa is dried too quickly.
The simplest forms of artificial driers are convection driers or Samoan driers which consists of a simple flue in a plenum chamber and a permeable drying platform above.
Air inlets must be provided in order to allow the convection current to flow without allowing smoke to taint the beans. These driers are simple to construct and have been used in Western Samoa, Cameroon, Brazil (the Secador drier) and the Solomon Islands.
Other artificial driers are platform driers using heat exchangers, where the hot air is kept separate from the products of combustion which pass to the atmosphere, or direct fired heaters, where the products of combustion mix with the hot air and are blown through the beans.
These driers can use oil or solid fuels as a source of power. The addition of a fan forces the hot air through the beans and creates a forced draught dryer.
Another type of dryer uses conduction. Drying platforms built of slate or cement are heated at one end by a fire or heat source. Small versions of these using oil drums with flues embedded in cement were used in Cameroon at one time and were known as Cameroon Dryers. Heat distribution is not uniform with this type of dryer.
Other techniques have been used in association with the above to overcome the problem of turning or raking the beans in the dryer – stirring the beans in a circular bed or turning the beans in a rotary drum.
Time and Types of Cocoa Harvests
The cocoa harvest is not confined to one short period but is spread over several months once or twice a year. The timing of the cocoa harvest varies from country to country, depending on the climate and the variety of cocoa.
In countries with a pronounced wet and dry season, the main crop occurs 5-6 months after the start of the wet season.
The percentage of crop harvested in the Main Crop (MC) season and the Light-Crop (LC) season will vary from country to country.
The biggest differential between main and mid/light crop harvests is in Africa where the light-crop accounts for about 15%-20% of the total harvest; in other countries the differential is not so obvious.
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