Theobroma Cacao

The genus Theobroma consists of some twenty-two species of small bushes and trees. Theobroma cacao is the only one of commercial value and this species is divided into two main groups:

• Criollo
• Forastero

There is a third group known as “Trinitario” which is basically a cross of the two.

Cultivation - The growing conditions required by the cocoa tree are fairly precise and the areas of cultivation lies within 20 degrees latitude of the equator.

• Temperature in cocoa growing areas is usually between 30C and 32C. The minimum allowable is 18C.
• Rainfall levels of 1,150 to 3,000mm are required.
• Soil conditions can vary considerably but a firm roothold and moisture retention are necessary.
• It is traditional for cocoa to be grown under shade trees although such conditions resemble those in its natural habitat it has been shown that higher yields can be obtained without shade if sufficient moisture and nutrients are made available.
• Propagation by seed is the most economical way of increasing stock but vegetative methods can also be used and these provide

Cacao trees are farmed as any other crop, though they grow in tropical regions.  The fruit of the cacao tree (called a “cacao pod”) is sweet and attracts monkeys or other wildlife who eat the fruit but do not eat the bitter seeds. The seeds are discarded in the natural setting thus allowing new trees to grow. The seeds cannot be released from the fruit unless some type of animal actually breaks the fruit open. It is the bitter seeds, packed with theobromine and caffeine, which are used to make chocolate. 

Fermentation - Workers cut the pods from the trees with knives attached to long poles, or with machetes. They gather the pods into heaps, cut them open and scoop out the beans. The beans are then placed in piles, covered with banana leaves, and allowed to ferment. Fermentation is carried out in a variety of ways but all depend on heaping a quantity of fresh beans with their pulp and allowing micro-organisms to ferment and to produce heat. Most beans are fermented in heaps. Better results are obtained by the use of fermentation boxes which give more even fermentation.

The sterile pulp gets inoculated with a variety of microorganisms from the machete, workers' hands, carrying-baskets, and fermentation boxes. During the first 24 hours, the seeds germinate and plant enzymes hydrolyze the sucrose to glucose and fructose. As microbes grow on the sugars, they produce heat which is trapped by the cover on the heap. The temperature in the fermentation heap reaches 40-50°C which kills the plant embryo. Fermentation takes five to six days.

Forastero beans take rather longer to ferment than Criollo. During the first day the adhering pulp becomes liquid and drains away. By the third day the mass of beans will have fairly even heated to 45 degrees C and will remain between this temperature and about 50 degrees C until fermentation is completed. It is necessary to occasionally stir the beans to aerate and to ensure that the beans initially on the outside of the heap are exposed to temperature conditions prevailing in the interior.

Detailed Fermentation - Due to microbial or ecological succession when each organism starts growing it alters the environment and inhibits its own growth but the new conditions are favorable for another species. The pulp contains mostly water with 10-15% sugars. The high sugar content in the pulp favors the growth of yeasts which ferment sugars to ethyl alcohol in the anaerobic heap. Eleven different species of yeasts have been isolated with Saccharomyces cerevisiae, and of that group, Candida rugosa, and Kluyveromyces marxianus are the most abundant. In addition to producing ethyl alcohol, the yeasts hydrolyze the pectin that covers the seeds. Experimental fermentations indicate that S. cerevisiae decreases the bitterness of the final product. Without pectin, the bitter alkaloids may leach out of the seed or be altered by alcohol that can now enter the seeds.

The yeast are killed by the alcohol they produce and, as the temperature rises, lactic acid bacteria such as Lactobacillus and Streptococcus grow. The pulp is stirred and drained to aerate it. The presence of oxygen and the lower pH now favor the growth of acetic acid bacteria, Acetobacter and Gluconobacter. After five days, the fermented mass contains up to 10⁸ microbes per gram. The beans are then dried and as they dry, molds including Geotrichium grow. Geotrichium oxidizes the lactic acid to acetic acid and succinic acid.

If fermentation is allowed to continue beyond five days, microbes may start growing on the beans instead of on the pulp. Off-tastes result when Bacillus and filamentous fungi, including Aspergillus, Penicillium, and Mucor, hydrolyze lipids in the beans to produce short-chain fatty acids. As the pH approaches 7, Pseudomonas, Enterobacter, or Escherichia may grow and produce off-tastes and odors.

Drying - After fermentation, the beans are dried in the sun. In some growing areas where the main harvest coincides with the dry season, sun drying is adequate. The beans are dried by being spread out in the sun in layers a few centimetres thick.

Roasting - These beans are then lightly roasted so the hull can be removed easily. This is the most important stage in the development of flavour. This can be achieved by roasting the whole bean, the cocoa bean cotyledon or even the ground cocoa bean cotyledon (cocoa mass). For chocolate production the roasting temperatures are 100C to 104C. For cocoa powder production higher temperatures of 120 to 135C are used. There are many designs of roasters: both batch and continuous systems. The operation is controlled so that: the nib is heated to the required temperature without burning the shell or the cotyledon and producing undesirable flavours; the heat is applied evenly over a long period of up to 90 minutes to produce even roasting; the nib must not be contaminated with any combustion products from the fuel used and provision must be made for the escape of any volatile acids, water vapour and decomposition products of the nib. After roasting the beans are cooled quickly to prevent scorching

Winnowing - The crushed material is winnowed to remove the broken pieces of shell. This is achieved by sieving and blowing air through the material.

Alkalisation - Alkalisation is a treatment that is sometimes used before and sometimes after grinding to modify the colour and flavour of the product. This was developed in the Netherlands in the last century and is sometimes known as “Dutching”. This involves soaking the nib or the cocoa mass in potassium or sodium carbonate. By varying the ratio of alkali to nib, a wide range of colours of cocoa powder can be produced. Complete nib penetration may take an hour. After alkalization the cocoa needs to be dried slowly.

Grinding - The cocoa nib is ground into “cocoa liquor” (also known as “unsweetened chocolate” or “cocoa mass”). The grinding process generates heat and the dry granular consistency of the nib is turned into a liquid as the high amount of fat contained in the nib melts.

Crushing - The shell will have been already loosened by the roasting. The beans are then lightly crushed with the object of preserving large pieces of shell and nib and avoiding the creation of small particles and dust. The older winnows used toothed rollers to break up the beans but modern machines are fitted with impact rollers. These consist of two hexagonal rollers running in the same direction that throw the beans against metal plates. The cocoa bean without its shell is known as a “cocoa nib”. The valuable part of the cocoa bean is the nib, the outer shell being a waste material of little value.

Conching - After crushing the chocolate is conched. The original conche was a tank shaped rather like a shell in which a roller is pushed to and fro on a granite bed. During the conching process which may last for several hours the chocolate is heated, this helps to drive off volatile acids, thereby reducing acidity when present in the raw bean, and the process finishes the development of flavour and makes the chocolate homogeneous.

Tempering - After conching the chocolate has to be tempered before it is used for moulding. Tempering involves cooling and reaching the right physical state for rapid setting after moulding.

Production of cocoa butter - Cocoa butter can be extracted using extrusion, expeller, or screw presses. Cocoa butter can be produced from whole beans, and mixtures of fine nib dusts, small nibs, and immature beans. Sometimes, whole nibs are pressed when the expeller cake is needed for the manufacture of coatings and therefore must be free from shell and as low as possible in cocoa butter content. When pressing whole beans, very light roasting or even no roasting is needed, and this gives the mild-flavoured cocoa butter that is desirable for milk chocolate. Hydraulic presses Hydraulic presses are used to produce cocoa powder and cocoa butter. Cocoa powder can be prepared by the hydraulic pressing of finely ground cocoa liquor. This can be achieved by compressing the liquor in heavy steel pots until a predetermined amount of cocoa butter is squeezed through very fine mesh screens or filters situated at each side of the pot. The pots, each with a capacity of about 18kg, are mounted in a horizontal frame and the cocoa liquor, heated to 93-102oC, is pumped in at a pressure of up to 300lb per square inch. Cocoa butter immediately starts to be forced out through the filter screens and when the pots are full the pressure pump is turned off and a hydraulic ram set in motion. A pressure of up to 6000lb per square inch is then applied. Cocoa butter runs from the pots to a trough and eventually to a collecting pan situated on a balance. When the required amount of cocoa butter has been extracted the ram is reversed to the starting position, the press pots open up and the cocoa cakes from each pot are deposited on a conveyor and taken away for grinding. The extracted cocoa butter will need to be cleaned to remove non-fat solids in suspension, this can be done by filtration or centrifugally. Cocoa butter produced by this method is normally a very pale yellow colour and it sets at a fairly hard fat showing crystal formation. Its melting point is 35oC.

The production of cocoa powder - The cocoa powder is taken from the press as a cake. It is broken in a mill. The resulting powder is sieved through fine silk, nylon or wire mesh. Most cocoa powders are made from mass which has been treated with alkali with the purpose of controlling the colour of the powder and improving the dispersability.

The production of plain chocolate - To produce plain chocolate mass is mixed with sugar and sufficient cocoa butter to enable the chocolate to be moulded. The ratio of mass to sugar varies according to the national taste. Melenging The mixture is ground to such a degree that the chocolate is smooth to the palate. At one time this was done by a lengthy process in “melengeurs” - heavy granite rollers in a revolving granite bed - but grinding is now done in a series of rolls.

The production of milk chocolate - Similar processes are involved in the manufacture of milk chocolate. The milk is added in various ways either in powder form to the mixture of mass, sugar and cocoa butter, or by condensing first with sugar, adding the mass and drying this mixture under vacuum. This product is called ‘crumb’ and this is ground and conched in a similar manner to plain chocolate.

• Cocoa butter (the fat removed from the cacao bean),
• Cocoa powder (the residue left over from the pressing of the cacao beans), and
• Chocolate liqueur (the ground cacao bean before cocoa butter and cocoa powder are produced).

With various formulations of adding milk, sugar, vegetable oils etc., this is the modern chocolate that is the refined, adulterated, product that has lost much (most) of its health properties - instead of the original chocolate the ancient people used for medicinal purposes.

Medicinal Use - Theobromine, the alkaloid contained in the beans, resembles caffeine in its action, but its effect on the central nervous system is less powerful. Its action on muscle, the kidneys and the heart is more pronounced. It is used principally for its diuretic effect due to stimulation of the renal epithelium; it is especially useful when there is an accumulation of fluid in the body resulting from cardiac failure, when it is often given with digitalis to relieve dilatation. It is also employed in high blood pressure as it dilates the blood-vessels. It is best administered in powders or cachets.

Dosage - Theobromine, 5 to 10 grains.

Contraindications - Veterinary - Chocolate is directly toxic to dogs because of theobromine. The more chocolate liquor - the more theobromine is present. This makes baking chocolate the worst, followed by semisweet and dark chocolate, followed by milk chocolate, followed by chocolate flavored cakes or cookies. Theobromine causes:

• Vomiting
• Diarrhea
• Hyperactivity
• Tremors
• Seizures
• Racing heart rhythm progressing to abnormal rhythms
• Death in severe cases

Toxic doses of theobromine are 9mg per pound of dog for mild signs up to 18 mg per pound of dog for severe signs. Milk chocolate contains 44mg/ounce of theobromine while semisweet chocolate contains 150mg/ounce, and baking chocolate contains 390 mg/ounce. It takes nearly 4 days for the effects of chocolate to work its way out of a dog’s system. If the chocolate was only just eaten it may be possible to induce vomiting; otherwise, hospitalization and support are needed until the chocolate has worked its way out of the system.

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