Organisation: Asian and Pacific Coconut Community (APCC) (http://www.apcc.org.sg)
2.1 Pre-Harvest Operations
Bearing coconut palms produce nuts throughout the year, although yields may vary with the season. A normal-bearing, adult palm produces at least one matured ready-to-harvest bunch of coconuts every month. Depending on the variety, the number of nuts per bunch can vary from 5 to 15. The theoretical number of bunches per palm that can be harvested annually is about 14 from tall coconut varieties and 16 from the dwarf species.
2.1 Pre-Harvest Operations
It usually takes 12 months for a nut to mature from pollination to harvest. Husk colour is the best indicator of coconut maturity. To attain good quality products, it is advisable that coconuts be harvested at the right maturity. Thus, only nuts that are partially or completely brown should be harvested. Nuts harvested at the tenth month or colour-break stage, should be stored or seasoned for some time to increase copra and oil yield.
To obtain maximum copra and oil recovery, nuts must be harvested when fully ripe. At this age of maturity, the estimated age is from 11 to 12 months. Although this stage is ideal for copra-production, in practice, green and immature nuts (about ten months old) are sometimes included during harvest especially as harvesters are paid on a per nut basis in certain countries.
Immature nuts when converted into copra will produce rubbery copra with low oil recovery. Rubbery copra is also susceptible to insect and mould attack due to its high moisture content. Immature nuts should therefore be segregated for seasoning for about two to four weeks. Seasoning is done under a shed, preferably with a concrete or wooden floor.
In practice, the harvesting cycle varies from 45 to 60 or 90-day periods. However, considering the hired labour cost, the recommended harvesting cycle is every 45 days for practical and economic reasons. Two to three bunches of coconuts could be harvested from each palm if this cycle is followed. This harvesting cycle has been found to yield a good number of mature nuts with high copra and oil recovery.
2.2.1 Methods of Harvesting
The methods of harvesting coconuts vary among countries or even among provinces within the same country. Producers from certain countries, especially in the Pacific, do not harvest their coconuts. Mature nuts are just left to fall on the ground and gathered by the farmer or the members of the farming family at regular intervals.
There are two common methods of harvesting coconuts. These are the pole and the climbing method. A third method is only practised in Thailand, Malaysia and Indonesia. This procedure involves harvesting of mature coconuts using of trained monkeys.
The pole method of harvesting is common in many countries in the region. In this case a harvesting scythe attached to the end of a long bamboo pole is used. (See Figure 3).
Figure 3: Climbing Method of Harvesting Products Coconut
The palm-climbing device is useful and advantageous for harvesting operations in places where traditional palm climbers are not available. (See Figure 4). The device is more efficient than manual climbing. With its use around 80 trees are harvested a day. There is also no risk of falling from the tree. In research stations and seed farms, the gadget could be useful for breeding purposes.
Figure 4: Palm Climbing Device in India
Although both the pole and the climbing method of harvesting require considerable experience and skill to be performed safely and efficiently, each has its own advantages and disadvantages. Harvesting using bamboo poles is generally faster, more efficient, less tedious, and less dangerous when compared with climbing. With bamboo poles, a harvester could also harvest more nuts per unit of time from more trees. On the other hand, the advantage of harvesting by climbing is that the climber/harvester could clean and inspect the crown of the palm for pest and disease attack. However, the cuts made to construct steps in the trunk in certain countries to facilitate climbing make the trees less suitable for timber purposes and fractures serve as entry points for pests.
Harvesting coconuts by using trained monkeys is considered efficient and cost-effective especially in areas where labour has become scarce.
Coconut Dehusking and Splitting
After harvesting, the succeeding operations are collection of the nuts, ripening, and dehusking. Harvested nuts are usually gathered together on a single layer on the ground. If the soil is moist, there is always the tendency for the nuts to germinate. Hence, nuts are not allowed on the damp ground for a long time, but are moved to a drier place. As mentioned earlier, the nuts are kept for about a month to ripen on the ground. This practice promotes desirable changes in the greener or somewhat less mature nuts: the coconut meat is said to grow thicker and harder thus producing a better quality copra if copra is desired, or a more suitable material for desiccated coconut production. Immature nuts tend to produce rubbery copra. Producers claim that seasoning or storage of 10-11 month old green nuts for one month or so improves the coconut kernel. This reduces the tendency to produce rubbery copra. Also dehusking is easier.
Coconuts in the husk are very bulky. They are dehusked first before being transported in trucks or carts.
Dehusking is a manual procedure. The principal part of the dehusker is a sharp-pointed shard of steel (a part of the native plow) positioned vertically with the point up and the broader part firmly placed on the ground. The farmer-operator impales the coconut on the sharp point with a strong determined downward movement. A few impaling strokes loosen the husk, making it come off (usually) in one piece. (See Figure 5). Impaling requires accuracy and nerve. Hence it has been difficult to get dehuskers in countries that are still trying to set up coconut plantations.
Figure 5: Coconut Dehusking Tool
Since dehusked coconut is an important article of commerce locally, husking therefore becomes mandatory. The coconut husks are left with the farmer. In the places where there is a coir fibre industry, the husks may be sold to this industry. Most often the husks are not sold but are used as fuel for drying copra. If little or no copra is made, there is an accumulation of coconut husks.
Since the coconut meat is found well inside the nut and is firmly attached to the shell, certain steps are necessary before drying the coconut kernel.
After the coconut is dehusked, the hard but brittle shell is exposed and can be split open into two halves using a machete. The coconut water is drained off leaving the cups ready for the drying stage. The meat is still attached to the shell. During the drying process, the meat shrinks and is easily detached or scooped out from the shell. These cups of coconut meat are then dried further.
Some farmers also practice nut splitting using a heavy machete even without dehusking the coconut. After nut splitting, the water is allowed to drain off. With meat still attached to the shell and the shell to the husk, the halved nuts are dried under direct sunlight. During the drying process the meat becomes detached or is scooped out from the shell with a scooping knife. The cups of meat are then further dried into copra.
2.5 Copra Processing
Copra is produced after drying the coconut kernel. Copra and the coconut oil as well as the cake derived from it are a major source of foreign exchange for many coconut growing countries in Asia, the Pacific, and Africa.
The quality of copra and copra cake is influenced by the method and the manner of drying the coconut kernel. Improperly dried copra gives rise to certain moulds, the most harmful of which is the yellow green mould called Aspergillus flavus and other aflatoxin related moulds. Aflatoxin is harmful both for man and animals.
It is therefore extremely important that the coconut kernel be properly dried to prevent the attack of aflatoxin related moulds. Processing of mature nuts to copra has several problems. Improper processing results in low oil yield and incidence of aflatoxin. Proper post-harvest practices, as well as proper drying and storage can increase the oil yield to about 20 percent. Proper drying of coconut results in copra with lower moisture content and lower incidence of aflatoxin.
Copra is mainly produced by small coconut holders using sun drying or smoke-kiln methods. Hot-air dryers are also used to a limited extent.
Copra making involves different steps between harvesting and marketing of the produce. Of these, drying the coconut kernel or reducing its moisture content from 50 percent to 6 percent most influences the quality of the product.
The following are ten guidelines for producing aflatoxin-free copra:
1) Harvest only fully matured (brown) nuts. These are the 12-month old or older nuts;
2) Do not pay the harvester for immature (green) nuts; instead penalise them for picking green nuts;
3) For producers selling husked nuts to desiccated coconut factories, segregate the "fouls" for processing into copra. Never mix the "regular copra" with the copra from "foul" nuts. They tend to have high mould growth;
4) When preparing copra, split the nuts and expose the meat only when certain that drying can start immediately or within four hours from splitting (exposure) to prevent mould formation. When there is the threat of bad weather, defer nut splitting;
5) If the weather suddenly turns bad during the sun-drying period and is expected to remain so for some time, use of mould inhibitors is recommended;
6) For producers practising sun drying, maintain cleanliness in the drying area. Clean pavement or floors before spreading fresh coconut meat. Make sure that soil and other extraneous matters are not mixed with the meat. Plastic sheeting may be used under the coconut meat to avoid direct contact with the ground;
7) Have on hand a portable cover (plastic sheeting) to protect coconut meat from rain and dew. These are shaped like roofing (inverted Vs) to allow aeration. On extended downpours, heat and dry the copra within 24 hours;
8) Continuous sun drying for four to five days (in good sunlight) shall achieve 6 percent moisture content;
9) For producers using smoke, kiln dryers, and other types of dryers, a drying temperature of 35oC to 50oC should be maintained for the first 16 hours of drying followed by 50oC during the next phase until a final moisture content of 6 percent if reached. It is important that drying should begin four hours after the nuts are split to prevent mould contamination;
10) Pressing the copra between the thumb and forefinger, the thumb against the whitemeat is a quick test for 6 percent moisture content. If the copra kernel (white portion) does not stick to the thumb, and readily drops when released, the 6 percent (approximately) moisture level has been achieved.
There are several methods and practices in drying the coconut kernel or in making copra. The methods vary from that which is considered primitive and traditional to one that adheres to certain scientific principles of drying.
The three common methods of drying are: a) sun drying or solar drying; b) kiln drying which is either direct on semi-direct drying; and c) indirect drying using hot-air dryers.
2.5.1 Sun Drying
Where weather conditions permit, sun drying can produce good quality copra. This method is used only during the dry season and when drying only small quantities of nuts. (See Figures 6 and 7).
Figure 6: Sun Drying Copra
Figure 7: Coconut Dehusking Tool
Since sundrying requires no expenses for fuel, the overall drying cost is considerably cheap compared to other copra drying methods using fuel-fed dryers. Fuel saved could mean possible additional farm income when sold or transformed into high value products like coconut shell charcoal, activated carbon, coir, etc., leading to the maximum utilisation of farm resources. Because the dryer is capable of producing clean, white and edible copra, copra produced should command a premium price. Moreover, its adoption could promote a high degree of consciousness in the production of superior quality export products.
2.5.2 Kiln Drying
There are two types of smoke dryers commonly used by coconut farmers, namely: the direct and semidirect types. Primarily, both types have the same heating principle but differ only in design and manner of firing or charging fuel. The direct dryer is designed in such a way that the fire bed is directly located below the copra bed.
On the other hand, the design of semidirect dryer is superior to the direct type. The hearth where fuel charging/feeding is done is located on one side of the dryer, connected to the drying bed by a tunnelike flue.
Direct Smoke Copra Dryer
The direct smoke dryer is a commonly used by coconut farmers in many coconut producing countries in the world. The smoke dryer has a grill-platform usually of split bamboo which constitutes the drying area. Halved nuts in the shell are placed on this grill. Underneath the platform is a fire hearth where coconut shells and husks are burned slowly to provide the heat for vaporising the water from the coconut meat. Generally, there is no chimney. (See Figure 8). The coconut meat shrinks upon drying and may be removed or scooped out from the shell. The meat is then further dried in the smoked dryer.
Figure 8: Direct Smoke Copra Dryer
The basic features which make the direct smoke dryer preferred by farmers are the high thermal efficiency of the dryer (the coconut meat is directly heated), the low cost of construction (the component parts are available on the farm), the simplicity of the design and the low cost of fuel. However, copra produced from this dryer are usually dark, sooty with smoke and at times scorched. Since the fuel is burned inside a pit underneath the drying bed, the dryer has to be attended when it is in operation to prevent the dryer from burning.
Semi-Direct Copra Dryer
It is a simple structural design, cheap and easy to build. The dryer has a combustion pit located about 3 feet away from the drying bed. The hot combustion product is channelled to the drying bed via an underground tunnel. The dimension of the excavation pit is 6 feet in width, 12 feet in length and a depth of 4 feet. The pit floor of the firing chamber is slightly inclined upward toward the end portion, which is designed to direct the flow of heated air. Dry coconut husks are used for fuel. It has a capacity of 2,000 nuts which are dried after 20 to 25 drying hours with resultant moisture of 6 percent. (See Figure 9).
Figure 9: Semi-Direct Smoke Copra Dryer
Due to the ease of structural design and operation, needing only inexpensive and locally available construction materials, this dryer is deemed to be socially adaptable and economically ideal for small coconut farmers. Since the total construction cost is within the reach of small coconut farmers with minimal fuel costs , the over-all production cost per kilo of copra would be much cheaper. Reflecting that fuel consumption per batch is approximately 50 percent of nut capacity, the savings per coconut husk (50 percent) plus coconut shell has a higher commercial value. This would mean additional financial benefits for the coconut farmers.
2.5.3. Copra Drying Using Hot-Air Dryers
In drying copra using hot-air dryers, the coconut meat is dried by means of uncontaminated hot air that passes through the copra bed. Since the smoke does not come in contact with the kernel, the copra produced is clean and white. If properly done, copra-drying using hot-air dryers produces good quality copra with 6 percent moisture content.
There are quite a few hot-air dryer designs. The common ones are a) The Modified Kukum Hot-Air Dryer and b) The Cocopugon or the Brick Hot Air Dryer.
The Modified Kukum Dryer
The Modified Kukum Dryer is an indirect natural draught dryer measuring 1.83 m in width, 3.66 m in length and 2.13 m in height. About 2000 nuts (average size) can be accommodated (volume of drying bed: 2.8 m3). Its heat exchange is made up of three standard oil drums welded together with five semi-circular baffles installed alternately inside the drums at distance of 0.46 m. The furnace measures three feet in length and two feet in width and is made of steel plastered with 6 cm thick cement-ash mixture inside. The furnace is provided with a slanting grate and door to regulate air entry. A butterfly valve is also provided at the chimney to control the temperature. (See Figure 10).
Figure 10: Modified Kukum Hot-Air Copra Dryer
About 30 hours are needed to dry one batch to 6 percent moisture content. Based on a 10 hours operation time per day, drying takes three days. About 8.7 minutes are needed to produce one kilo copra with the modified Kukum dryer.
The Modified Kukum dryer produces good quality copra. However, maintenance and repair costs are the high. The metal parts of the dryer, which start to corrode as soon as the dryer is being constructed. Frequent use of the dryer will reduce corrosion, but never stop it. Since copra is a low price product, the use of stainless steel or even the application of primer is not economical. The exposure to high temperatures, aggressive fumes and water induce corrosion of the metal dryer components.
Cocopugon Hot-Air Brick Copra Dryer
The Cocopugon is a further improvement of the modified Kukum Dryer. Instead of using metal drums as the heat exchanger common in Kukum Dryers, the Cocopugon uses bricks. Bricks are known for their high strength, durability and dimensional stability.
The proportions of the Cocopugon are 260 cm in width, 360 cm in length and 200 cm in height. Standard fire bricks and 2.5" crown bricks are used for the chimney and the heat exchanger, respectively. The dryer can accommodate 2,000 average sized nuts per batch (volume of drying bed: 3.33 m3). To facilitate ease of loading and unloading, the right side of the drying bed wall is removable. A one step stair and platform is also provided on the same location. (See Figure 11).
Figure 11: Cocopugon Hot-Air Brick Copra Dryer
Unlike dryers with metal heat exchangers, this dryer needs to be preheated. Firing should be done first before loading the split nuts. The burner can accommodate about 200 to 300 husks. Refuelling has to be done every 3 to 5 hours. The heat stored in the bricks will be released slowly after the last firing on the first drying day, such that drying will continue for several hours without adding fuel (husks).
After a preheating time of 3.5 hours and a loading time of two hours, the average temperature in the bottom layer is 66.3ºC. The burner then has to be fed five to seven times for the whole drying period. Formerly, this could only be accomplished in one day at a feeding interval of about three to four hours assuming a constant fuel feed rate. Unloading could be done after the dryer has cooled down on the second day. If operated on a two days schedule, five firings are needed on the first day and another two to three firings on the second day. Unloading will be done the next morning to utilise the heat stored in the bricks. If the baffle in the chimney is closed during nighttime, embers can still be found inside the burner on the following morning making it easy to continue firing. The temperature curve for the burner has several small peaks indicating the maximum temperature per feeding interval. The effect on the drying bed temperature is minimal, thus having an almost constant drying temperature. Even if the burner is fully loaded, the resulting temperature in the drying bed does not exceed 90 to 95ºC, thus eliminating the risk of producing scorched copra.
Since the heat exchanger or the burner covers almost the whole area inside the dryer body, the temperature distribution is very uniform. The difference in temperature between the highest and lowest value is less than 5º Kelvin. A standard deviation of 3º Kelvin indicates a very constant temperature.
During operation, the dryer operator spends two hours per batch at the dryer, meaning the labour requirements are cut down by more than 50 percent to 4.1 minutes per kilogram copra compared with the modified Kukum dryer. The farmer can therefore leave the dryer in between fuel feedings and use his time for other activities.