Post harvest processing and Agricultural Engineering is responsible for research and development of agricultural post harvest technology such as,  a. To enhance coffee and cocoa competitiveness through the improvement on the processing technology and quality; b. To increase the added value of coffee and cocoa through the end products diversification; c. To reduce the environmental pollution by the utilization of coffee and cocoa processing waste to useful and valuable products; d. To develop systems for quality management and food safety; e. To design and build prototypes of various types of farm equipment, covering from on farm operation to post-harvest processing.

ACCOMPLISHEMENTS

Labor Saving Techniques and Production Efficiency

a. Pods splitting

To reduce the splitting cost and the number of cut beans, recently a mechanical pod breaker and beans splitter has been designed, Figure 1. The breaking of pods is carried out by using double roll rotated on the opposite direction at 20 – 25 rpm. The dimension of each roll is 150 mm diameter and 250 mm long. The broken husks and the beans fall down into the double screen which finally separated them according to their size. The broken husks retain on the screen, whereas the beans pass through it. The pod breaking capacity is about 10.000 pods per hr. The power requirement to turn the rolls and to shake the screen is 5.5 HP.

b. Reducing pulp content

To produce less acidic cocoa beans, the excessive thickness pulp covering the cocoa beans can be reduced partially by mechanical equipment. Less pulp means less by reducing the pulp, the acids production and the time of fermentation.   Figure 2 shows a continuous mechanical pulp reducer with a throughput about 2 tons per hr of fresh cocoa beans. It consists of a static sieve stainless steel drum with 300 mm diameter and 0.60 m long. A stainless steel shaft which is provided by four agitators is installed inside the drum and is rotated at a speed of 500 min^-1.by a 5.5 HP gasoline engine. The fresh beans are rubbed by the revolving agitator on the surface of the stationer perforated drum. The loosen pulp goes out through the holes and falls down to a basket under the drum. Every single ton of fresh cocoa beans can be collected approximately 125 – 150 kg of pulp.

Cocoa pulp can be easily formulated into a juice or refreshing drink by adding water and sugar to 11°Brix and pH 3.8. The juice is then pasteurized for 5 minutes at 80°C before packing. The pulp can also be used as a bacteria growth promoter for cocoa pods composting.

c. Fermentation

 Combining partial pulp removal and shallow box fermentation can improve cocoa fermentation process in terms of time and labor saving. The fermentation is carried out by adopting the shallow fermentation boxes as recommended by the Sime-Cadbury Process [Figure 3]. Single turning of the fermenting mass at the second day reduce the labor cost, while fermenting less pulp cocoa reduce the time. The dimension of a large box is 0.5 m deep, 1.20 m wide and 1.50 m long and its capacity is approximately 600 to 700 kg wet beans, whereas the small box has dimension 0.5 m deep, 0,40 m wide and 0,40 m long and its capacity is approximately 40 50 kg wet beans. Hardwood planks are still used as the primary material for constructing the boxes. The side and bottom walls of the boxes are provided with holes and slots. The diameter of the hole varies from 9 to 12 mm at 0.10 m grids. The gap of the slots is about 5 mm apart between two adjacent wood planks.

d. Solar Drying

Solar drying is used to avoid many cocoa quality problems arise from poor or inadequate drying of the beans, to reduce the impact on inferior flavor development by implementing slower drying and to minimize the drying cost. Slow drying cocoa beans on a raised platform in the sun is best, additional heat by using solar collector can also be used to minimize the dependence on the weather [Figure 4 and 5].

The solar tunnel dryer is originally designed by The University of Hohenheim, Germany. The modifications are then made in order to match with a local need and a local available material. The basic components of the collector are absorber, air duct and UV-stabilized transparent cover. The absorber made up from galvanized iron sheet painted black is used to receive insolation and convert it into heat. A centrifugal blower is installed in the inlet of the collector to force the ambient air through the air space between the absorber and the cover. The heated air then flow above the cocoa beans layer and take up the moisture. The air flow rate is approximately 1.000 m³ per hr in order to maintain the suitable drying air temperature of 40 to 50^o C. The dimension of the solar dryer is 2 wide and 20 m long. The capacity of the drying chamber is approximately 400 – 500 kg fermented cocoa beans. The drying time to remove moisture of cocoa bean from 50 - 55% to 7% is about 5 – 6 days based on the average daily solar radiation 3 – 4 kWh.

For a large scale of drying operated by a group of farmers, solar collector can be incorporated into the roof of processing building [Figure 6 and 7]. The solar collector is designed by using a modular system as shown in Figure 8. Each module consists of a black-painted galvanized iron sheet [as an absorber surface]; fixed on a rectangular wood frame of 0.75 m wide and 6 m long and transparent sheet cover. The backside of the absorber surface is covered by a sandwich of a 25 mm thick glass wool layer, a 0.60 mm thick aluminum foil sheet, and a mesh wire sheet.  Each module is installed one by one consecutively till the roof is completely covered. Ambient air is sucked over the entire surface of the solar collector through an air gap between the cover and the absorber surface. The hot air afterwards is forced into the drying chamber through the air channels.

The dryer is a flat bed batch type with dimension of 3 m wide, 6 m long and 1 m high. The capacity of the drying platform is approximately 5 tons fermented beans. The drying chamber is provided by a blower which is able to produce an optimum flow rate of 1.000 - 1.500 m³ per hr per ton of wet fermented cocoa beans. The final beans moisture content of 7% can be achieved within 68 to 110 hours depending on the depth of cocoa bed inside the drying chamber. Recommended deep bed is not more than 0.30 m to avoid irregular drying process due to difficulty in beans stirring. This cocoa processing center can also be built by an additional heat source from a fire wood furnace. To avoid smoke contamination to the bean, the drying is carried out by in direct heating through a tubes heat exchanger.

e.  Mechanical grading

It is important that the bean size distribution is as constant as possible. In general, larger beans are preferred because of the higher nibs to shell ratio. Moreover, flat beans, broken beans, pieces of placenta, fragments of pod, twigs and small stones can be removed by using a simple mechanical grader [Figure 9]. The vibrating sieve consists of three or four screens of different sized mesh depending on the amount of debris mixed on cocoa beans mass. More debris needs more screens. The top screen sieves out foreign matter larger than a normal bean size, such as double beans, bean clusters and fibrous matter. While the second screen retains the beans having beans account ranging from 85 – 90 and passes the beans having beans account more than 90 to 110. The third screen retains the beans having beans account more than 110 and lets the whole broken beans falling onto basket. The vibrating mechanism is driven by a gasoline motor of 5 HP.

f. Storage

Well graded cocoa should be stored properly at the farm level as a whole for extended periods due to the moisture, mould and FFA development. Before being shipped to the destination countries, well processed cocoa should be stored in well ventilated warehouse. Moreover, possible insect infestations need to be controlled by keeping good sanitation, cleanness and illumination within the warehouse. Figure 10 and 11 show the solar collector installed on the roof of the processing building use for conditioning the ambient air the store house. The heat from the solar roof collector which is injected during the day time will be stored by the bulk of cocoa beans within the jute bags. During the night, the heat which is deliberated will reduce the ambient relative humidity of the warehouse.

Development of Tools to Assess and monitor Quality Attributes

a. Colorimetric to measure the degree of fermentation

There is no chocolate flavor in cocoa beans without fermentation. During fermentation are formed compounds [precursors for chocolate flavor] that will react with each other at the roasting period to form chocolate flavor. Cellular structure and color inside the cocoa bean change during the fermentation process due acetic acid penetration through testa and high temperature induced by oxidation process. Both changes can visually be judged as a subjected quality indication after the beans are cut. Fifty pieces of dried cocoa beans are cut lengthwise through the middle by a simple tool [Figure 12].

Both halves of each bean are examined visually in full daylight by an experienced cocoa farmers or cocoa grader according to the cross-sectional color and structure of the beans, namely fully brown, partly purple-brown, fully purple and slaty, and are compared to a well defined standard color photos [Figure 13].

To obtain a quantitative and an objective indication, a series of experiment have been carried out to develop a simple, easy to use and affordable device to measure on the color change of cocoa beans influenced by the degree of fermentation process. Reflectance measurements [diffuse reflection] are performed with a sensor containing a light emitting diode [LED] and a photodiode in an optical configuration [Figure 14]. In a black plastic housing, two cylindrical holes of 5 cm diameter are drilled. One hole is perpendicular to the surface of the target object [a cocoa bean] on the opposite end containing a silicon photodiode. The second hole is drilled with an angle of 30^o relative to the first hole containing the LED. Both cylindrical holes join at the surface, where the target is situated, with an aperture of 5 cm diameter.

The tester is then calibrated by using the standard Fermentation index method [FI]. This is determined according to the method of Gur’eva and Tserevitinov. Ground cocoa nibs [0.5 g] are added to a mixture of methanol and HCl [concentration 37%] at a volume ratio of 97:3 and homogenized. The mixture is left in the cold room [temperature 8 ◦C] for 16–18 h and filtered using Whatman No. 1 filter paper. The filtrate is collected and the ratio of the absorbance at 460nm and 530nm was determined using a UV-visible spectrophotometer.

b. Development a digital moisture tester

Many cocoa quality problems arise from poor or inadequate drying of the beans and over drying. Too much moisture can encourage mould [fungal] growth, but too long drying at high temperature can cause over dying. For best results in drying, an accurate moisture test is needed to determine that the cocoa beans are dried at the right moisture and time. Beans moisture content may be determined by direct or indirect methods. Direct methods are commonly used for laboratory work where exact determination is critical. Heating the grain sample to drive off moisture and weighing before and after heating, according to a standardized procedure, to find water loss is a direct method.

Moisture of cocoa beans is measured indirectly by measuring the electrical capacitance of the beans. The commercially available moisture tester for cocoa may not be easy to buy in the local market. Besides, it is expensive, a reading on the moisture meter is converted to a moisture reading by use of a calibration chart or table rendering impractical for field use. ICCRI then develops a cocoa moisture meter that utilizes the electrical capacitance method [Figure 15]. To avoid using calibration chart during moisture measurement, the regression equation obtained during calibration process has been compensated into the microprocessor of the meter.

Cocoa beans act as dielectric materials when placed between concentric metal cylinders which form a capacitor. The dielectric constants for the dry components of grains [butter, cellulose, protein] vary between 2 and 5 while "free" water has a dielectric constant of 80. Because of the significant difference between the dielectric constants for water and dry components, changes in the moisture content will change the capacitance reading on the meter. In the range of 7 - 23% moisture content, the capacitance of the bean changes significantly with changes in moisture content. As the moisture content readings are affected by the density of packing and temperature. When grain is dropped into a container, the method of filling may cause variations in the porosity, which is the percentage of the volume of the container occupied by air. Porosity may vary from as low as 35% to as high as 65%. Since the dielectric constant for air is slightly greater than 1, the density of packing will have a great effect on the meter reading. Therefore, the method of filling the chamber is precisely controlled.

b. Temperature and relative humidity meter

Air temperature and air relative humidity influence drying speed. In general, at constant airflow rates, higher air temperatures and lower relative humidity increase drying speed. Rate of drying, which is related to drying temperature, is the major limitation on drying cocoa beans. At high temperature, the shell of the bean shrinks faster than the nib, causing cracks in the shell. Further handling results in breaking the shell rendering the mould infestation of the nib. Development of “off" flavors and increased spoilage can occur in the broken beans. Moreover, high drying rates can also harden the shell which hinders the acid removal from the nib rendering to acid taste. However, drying too slow at very temperature can cause too much moisture in the beans which encourage mould development. To control drying operation properly, in terms of quality and cost, the temperature and air relative humidity must be controlled at a selected condition thus need temperature and relative humidity meters.  The commercially available temperature and relative humidity meter may not be easy to buy in the local market. ICCRI then develops a cocoa moisture meter that utilizes the electrical component available in the local market [Figure 16 and 17].

The Utilization of Cocoa Farm and Cocoa Processing Waste to Useful and Valuable Products

a. Composting

Most cocoa farms are known for the abundance availability of biomass [organic raw material] which is useful for preparation of compost such as cocoa pods husk, shade tree trunks and braches and fresh leaf litter, weeds, succulent stems. Downsizing, or chopping up the biomass, is a widely-practiced technique to increase the surface area of the biomass available for microbial action and provides better aeration during composting process. This technique is particularly effective and necessary for harder materials such as cocoa pod husks, trunk and wood. The chopping mechanism is done by using high speed rotary cutters as shown in Figure 18. Typical output is chips on the order of two to three cm. The resulting chips have various uses such as being spread as a ground cover or being fed into a composting unit. The power for revolving the rotor is provided by a diesel engine of 15 Horse Power [HP] through a V rubber belt transmission.

The chopper can be portable, or being mounted on wheels frames suitable for towing behind a truck or a hand tractor unit in order to an easy moving from one to next location within the cocoa farm where collection points of cocoa pods husk are established [Figure 19].  The movable chopper is more economical because transportation cost of pods husk which generally are very voluminous can be reduced. Moreover, the chips resulted from chopping operation can be directly composted in the field which finally reduces the fertilization application cost as well.

The composting takes place between walls that form long, narrow channels referred to as beds. Composting can also be done in windrow [Figure 20].

The chips is piled loosely in a compost pen to provide better aeration within the composting beds, but it should not be too compact and no heavy weights should be placed on top. The pile is then moisturized by cow dung slurry till its moisture content increases to approximately 60 %.  Compost heaps is located in shady areas or covered with tarpaulin sheet. The heap of the chips is supported by a perforated platform made from bamboo mat and raised about 200 mm from the ground in order to provide adequate aeration at the bottom. Alternatively, aeration can be provided by placing perforated bamboo trunks horizontally and vertically at regular intervals. The heap is covered over completely to maintain the heat of decomposition, and minimize water evaporation and ammonia volatilization.

The aerobic composting process starts with the evolution of heat within the pile. The compost heap heats up in 24-48 hours. The temperature should be maintained at 50 °C or higher, and the heap should be turned every five to seven days for the first two weeks, and thereafter once every two weeks. In many cases, the temperature rises rapidly to 60 - 70 °C. First, mesophilic organisms [optimum growth temperature range = 20-45 °C] multiply rapidly on the readily available sugars and amino acids. They generate heat by their own metabolism and raise the temperature to a point where their own activities become suppressed. Then a few thermophilic fungi and several thermophilic bacteria [optimum growth temperature range = 50-70 °C or more] continue the process, raising the temperature of the material to 65 °C or higher. This peak heating phase is important for the quality of the compost as the heat kills pathogens and weed seeds.

The active composting stage is followed by a curing stage, and the pile temperature decreases gradually. The start of this phase is identified when turning no longer reheats the pile. At this stage, another group of thermophilic fungi starts to grow. The mature compost is obtained after 6 - 8 week. By the time composting is completed, the pile becomes more uniform and less active biologically although mesophilic organisms decolonize the compost. The material becomes dark brown to black in color. The particles reduce in size and become consistent and soil-like in texture. In the process, the amount of humus increases, the ratio of carbon to nitrogen [C: N] decreases, pH neutralizes, and the exchange capacity of the material increases. Table 1 shows the chemical composition of the cocoa pods husk compost compared to the various organic compost resulted from different raw materials.

Table 1. Chemical composition of the organic compost resulted from different raw materials.

For commercial purpose, the compost may be sun-dried until the moisture content is 20 - 23 percent, bagged into woven plastic sacks and are stored in a warehouse or shaded area [Figure 21].

b. Biogas production

Animal [cattle and sheep] based integrated farming system is getting popularity for cocoa farmers. It fits for small and medium scale farmers. It is not only eco-friendly, but also more economical for farmers to raise animals in an integrated farm for an additional income. The animals help in efficient recycling of organic crop residues. It becomes an easy source for farmers to procure organic manure. Farmers feed animals with green leaf from regularly pruning of shade trees [Figure 22].  Recently due to increasing price of kerosene, the waste obtained from the animals not only provides organically rich manure but also helps in manufacturing biogas. Biogas technology provides an alternative and a cheap source of energy that meets the basic need for cooking fuel in rural areas. Using locally available resources such as cattle waste and other organic wastes, both manure and gas are derived. A 3-cubic meter biogas plant can provide a steady supply of fuel to an individual farmer.

Biogas can also be produced by using chopped cocoa pod husks and fermentation sweating mixed with a proportion amount of cattle manure as inoculums in a simple reactor [Figure 23]. Before being loaded to the reactor, chopped cocoa pod husk is soaked in water for 3 to 5 days to dissolve tannin contents and mixed with cocoa dung. Higher proportions of cattle manure reduced the inhibitory effects of fresh pod husks in the production of biogas. The digestion time is about 30 - 45 days till the regular biogas production is resumed.

The central part of an  is an enclosed tank known as the digester. This is an airtight tank filled with the chopped cocoa pod husk and cow manure slurry with weight proportion 1: 1. Dependent on the waste material and operating temperature, a batch digester will start producing biogas after two to four weeks, slowly increase in production then drop off after three or four months. Batch digesters are therefore best operated in groups, so that at least one is always producing useful quantities of gas. Some method of stirring the slurry in a digester is always advantageous, if not essential. If not stirred, the slurry will tend to settle out and form a hard scum on the surface, which will prevent release of the biogas. Continuous feeding causes fewer problems in this direction, since the new charge will break up the surface and provide a rudimentary stirring action.

The biogas is collected in used inner tube of car tires. The biogas flows through a valve in the tube. A non-return valve here is a valuable investment to prevent air being drawn into the digester, which would destroy the activity of the bacteria and provide a potentially explosive mixture inside the drum. The biogas from the tube can be directly burn in a simple burner. To ensure that the pressure in the system is correct, large loads may need to push the tubes or to transfer the biogas into a steel tank by using a manual pump [Figure 24].

DISSEMINATION AND COMMERCIALISATION

The results of research activities are forwarded to users through scientific and technical publications, web-site, seminar, workshops, training, and direct technical guidance and supervision. The application of the research outcome is continuously monitored to evaluate that the results give noticeable impacts on the users. The constraint of research results application might be more of social and educational aspects. The users require information program which shows that research results are able to provide benefit in economic sense. A well coordinated research-development-demonstration programs for creating awareness is required for proper implementation of new technology.

National and international relevant research organizations, NGO and industries should be identified and entrusted with the responsibility of evaluating techno-economic aspect of different designs and validating the models through extensive field testing. Figure 25 and 26 show the solar dryer installed in Lara [Sulawesi] and activities about the composting training that ICCRI are working closely with PT. Mars Symbioscience Indonesia.