Grading, Storage and Marketing of Dry Cocoa Beans
Checking the quality of cocoa beans and its marketing: the quality of cocoa beans is checked through sampling. The sampler selects at random a significant percentage of the bags for inspection and a stabbing iron is used to draw a number of beans from the selected bags. Or, if the cocoa is in bulk, samples are taken at random from the beans as they enter a hopper or as they are spread on tarpaulins.
Different authorities may set a differing level of beans/samples for inspection. The International Standard recommends that the samples should amount to not less than 300 beans for every ton of cocoa.
For bagged cocoa, samples should be taken from not less than 30% of the bags, and for bulk cocoa there should be not less than 5 samplings per tonne.
The samples are analyzed using the cut test. Most exporting countries’ authorities specify standards dependent on the International Standards Organization cut test, as do normal physical cocoa contracts.
The cut test provides an assessment of the beans from which analysts may infer certain characteristics of the cocoa, which gives an indication of quality.
The cut test involves counting off 300 beans. These 300 beans are then cut lengthwise through the middle and examined. Separate counts are made of the number of beans which are defective in that they are mouldy, slaty, insect damaged, germinated or flat.
The results for each kind of defect are expressed as a percentage of the 300 beans examined. The amount of defective beans revealed in the cut test gives manufacturers an indication of the flavour characteristics of the beans.
Bean counts are another measure of quality that producing countries often use, though there is no internationally accepted bean size classification. The Federation of Cocoa Commerce defines the following method for bean counts:
A sample of not less than 600 grams of whole beans, irrespective of size but not including flat beans, will be counted to obtain the number of beans per 100 grams. The Ministry of Agriculture through the Produce Inspection Unit is responsible for Quality Control.
Further tests are carried out by chocolate manufacturers and cocoa processors, particularly for beans from origins that are inconsistent in quality or prone to off flavours. The manufacturer cannot sift out all the defective beans and so must ensure good quality at the selection stage.
Consistency in quality for the production of cocoa mass cannot be achieved when using one source of cocoa beans because of the large natural variability which exists in each lot.
The differences can be reduced by having a number of different types and lots of cocoa beans of known quality in stock and making an appropriate blend. Strict control of the roasting and alkalizing processes is also required to produce the best quality.
For the chocolate manufacturer the yield of nib is very important, as is the amount of cocoa butter in the nib. Higher levels of cocoa butter mean that lower levels will need to be added later on in the manufacturing process. Nib yields are determined in the laboratory.
Flavour is also important for chocolate manufacturers. Flavour assessment is normally carried out by panels of between five and ten experienced tasters. Off flavours can readily be detected by tasting roasted ground nib of cocoa liquor directly or they can be mixed with sugar and water to make a basic dark chocolate before tasting.
Mouldy and smoky off flavours and excessive bitterness cannot be removed during processing. Acid tastes can be altered in processing through neutralization.
Substandard beans can be pressed whole to produce expelled cocoa butter which is then refined. Better quality beans are deshelled before pressing to produce pure pressed cocoa butter and cocoa press cake (which ultimately becomes cocoa powder).
Chocolate manufacturers have a number of requirements with respect to the quality of cocoa butter: hardness, melting and solidification behaviour.
Factors to Consider In the Storage of Cocoa Beans In Order To Minimize Risk
The warehouse should have cement or non-flammable floors without cracks and crevices for insects to hide in;
Ideally the floor level should be higher than the surrounding land to prevent flooding and to allow water to flow away;
Walls should be of non-flammable material without cracks and crevices;
Adequate ventilation is necessary to prevent an increase in mould;
The roof should be insulated but should not be made of wood;
Bags may be bulk-stowed but ideally the bottom layer should be on pallets allowing an air space of 5-10cm and the top layer should be at least 1m away from the roof. The stacks should also be positioned away from outside walls;
Fumigation and other forms of insect control can be carried out to ensure that the products are pest-free;
The cocoa should be regularly inspected;
No other products should be stored with the cocoa to prevent contamination;
Access to the storage areas can be controlled.
Processing of Dried Cocoa Beans
During the subsequent processing of the cocoa beans the beans are cleaned and can then undergo a form of thermal pre-treatment to separate the shell from the bean.
One form of thermal pre-treatment uses infra-red technology in which the beans undergo infra-red radiation on a fluidized bed or vibrating conveyor. Water accumulates on the surface of the bean and bursts the shell.
The high surface temperature induced by this process brings about a drop in the amount of microbiological contamination, especially yeast and other fungi.
The beans are then separated from the shells and roasted. Following roasting the beans are turned into cocoa massby grinding.
The quality of the cocoa mass is important due to the natural variability which exists in cocoa. Quality criteria for cocoa mass include figures for the number of yeasts found per gram – maximum 50, and for alkalized cocoa powder – a normal maximum of 50 with a limit of 100.
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Products of Cocoa
Physical and chemical information on cocoa beans, butter, mass and powder
The physics and chemistry of cocoa beans and cocoa products is very complex and changes throughout the life of the bean, depending on the processing it receives.
The following gives an indication of the changes in the bean through its life, together with some references that give further more detailed information on the physics and chemistry of cocoa beans.
Cocoa Beans
Cocoa beans are the seeds of the tree Theobroma cacao. Each seed consists of two cotyledons (the nib) and a small embryo plant, all enclosed in a skin (the shell). The cotyledons store the food for the developing plant and become the first two leaves of the plant when the seed germinates.
The food store consists of fat, known as cocoa butter, which amounts to about half the weight of the dry seed. The quantity of fat and its properties such as melting point and hardness depend on the variety of cocoa and the environmental conditions.
The seeds are fermented which causes many chemical changes in both the pulp surrounding the seeds and within the seeds themselves. These changes cause the chocolate flavour to develop and the seeds to change colour.
The seeds are then dried and despatched to processors as the raw material for the production of cocoa mass, cocoa powder and cocoa butter.
The first stage of processing includes roasting the beans, to change the colour and flavour, and shell removal. After roasting and deshelling an alkalizing process can take place, to alter flavour and colour.
One analysis of the chemical composition of beans after fermentation and drying is as follows:
| Nib % Maximum | Shell % Maximum | |
| Water | 3.2 | 6.6 |
| Fat (cocoa butter, shell fat) | 57 | 5.9 |
| Ash | 4.2 | 20.7 |
| Nitrogen | ||
| Total nitrogen | 2.5 | 3.2 |
| Theobromine | 1.3 | 0.9 |
| Caffeine | 0.7 | 0.3 |
| Starch | 9 | 5.2 |
| Crude fibre | 3.2 | 19.2 |
This gives an indication of the chemical composition of the bean but it must be remembered that this will vary depending on the type of bean, the quality of the fermentation and drying and the subsequent processing of the bean.
Cocoa Mass or Liquor
Cocoa mass is produced by grinding the nib of the cocoa bean. The quality of the cocoa liquor will depend on the beans used. Manufacturers often blend different types of beans to gain the required quality, flavour and taste.
The cocoa liquor can undergo further roasting and alkalisation to alter the colour and flavour which will also alter its chemical composition.
Cocoa Butter
The fat or cocoa butter can be extracted from the bean in a number of ways. Pure press butter is extracted from the cocoa mass by horizontal presses. Sub-standard cocoa beans can be pressed without deshelling by using continuous expeller presses. Pure press butter needs no cleaning but it is often deodorized.
A solvent extraction process can be used to extract butter from the cake residue left after the expeller process; this type of butter must be refined.
Cocoa butter obtained by pressing the cocoa nib exhibits the following properties: brittle fracture below 20ºC, a melting point about 35ºC with softening around 30-32ºC.
Cocoa butter is composed of a number of glycerides. Two studies established that the percentage of the constituent glycerides is as follows:
| Glycerides | Percentage |
| Trisaturated | 2.5 to 3.0 |
| Triunsaturated (triolein) | 1.0 |
| Diunsaturated | |
| Stearo-diolein | 6 to 12 |
| Palmito-diolein | 7 to 8 |
| Monounsaturated | |
| Oleo-distearin | 18 to 22 |
| Oleo-palmitostearin | 52 to 57 |
| Oleo-dipalmitin | 4 to 6 |
Cocoa Powder
Cocoa powder is formed from the cocoa mass. Presses are used to remove some of the fat and leave a solid material called cocoa press cake.
These cakes are then crushed to form cocoa powder. The processing can be altered to produce cocoa powders of different composition and with different levels of fat.
An indication of the composition of cocoa powder is as follows, but it must be remembered that this will be different depending on the roasting, alkalization and pressing processes undertaken:
| Components | Percentage |
| Moisture % | 3.0 |
| Cocoa butter | 11.0 |
| pH (10% suspension) | 5.7 |
| Ash % | 5.5 |
| Water soluble ash % | 2.2 |
| Alkalinity of water soluble ash as | |
| K2O in original cocoa % | 0.8 |
| Phosphate (as P2O5) % | 1.9 |
| Chloride (as NaCl) % | 0.04 |
| Ash insoluble in 50% HCl | 0.08 |
| Shell % (calculated to unalkalised nib) | 1.4 |
| Total nitrogen | 4.3 |
| Nitrogen (corrected for alkaloids) % | 3.4 |
| Protein | |
| Nitrogen corrected for alkaloids x 6.25 % | 21.2 |
| Theobromine % | 2.8 |
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