|By goGreen | July 19, 2012|
The cocoa tree (Theobroma cacao) is a native of the dense tropical Amazon forests where it flourishes in the semi-shade and high humidities, but wild varieties also occur from Mexico to Peru. The Mayas of Yucatan and the Aztecs of Mexico cultivated cocoa long before its introduction to Europe, and Montezuma, Emperor of the Aztecs, is stated to have consumed regularly a preparation called chocolate made by roasting and grinding the cocoa nibs, followed by mashing with water, maize, anatto, chili and spice flavors. The richness of this mixture no doubt had some connection with the Aztec belief that the cocoa tree was of divine origin and later led the Swedish botanist, Linnaeus, to give the name Theobroma – Food of the Gods – to the genus including the cacao species. The Aztecs also considered the drink to have aphrodisiac properties.
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:
There is a third group known as Trinitario which is basically a cross of the two.
The growing conditions required by the cocoa tree are fairly precise and the areas of cultivation lie within 20° latitude of the equator. The temperature in cocoa growing areas is usually between 30C and 32C. The minimum allowable is 18C. Rainfall levels of 1,150 to 3,000 mm are required. Soil conditions can vary considerably but a firm root hold 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 a more consistent and reliable method of reproducing trees of particular strains.
Cocoa beans are fermented not just to remove the adhering pulp but also develop the distinctive flavor of cocoa. Correct fermentation and drying of cocoa is of vital importance and no subsequent processing of the bean will correct bad practice at this stage. A good flavor in the final cocoa or chocolate is related closely to good fermentation but if the drying after fermentation is delayed molds will develop which will produce very unpleasant flavors. After the pods are cut from the trees the beans with the adhering pulp are removed. 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. 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°C and will remain between this temperature and about 50°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.
After fermentation the beans are placed in shallow trays to dry. 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 centimeters thick. Sun drying trays may be movable on rails so that they can be pushed under canopies. Where the weather is less sunny, artificial driers are used. There are numerous types of dryers but an essential feature of all must be that any smoky products of combustion do not come in contact with the beans otherwise taints will appear in the final product. Some system involve the complete combustion of the fuel so that the flue gases can be used to dry the beans.
The beans are cleaned to remove the following extraneous matter: bean clusters and other large pieces using rocking and vibratory sieves; light material like dust, loose shell and fiber using a gentle upward air stream; iron particles using a magnetic separator and stones and heavy material using a fluidized bed with air aspiration to lift the coca beans. It may also be necessary to grade the coca beans according to size to ensure even roasting.
This is the most important stage in the development of flavor. 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 flavors; 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 vapor and decomposition products of the nib. After roasting the beans are cooled quickly to prevent scorching.
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.
The crushed material is winnowed to remove the broken pieces of shell. This is achieved by sieving and blowing air through the material.
Alkalisation is a treatment that is sometimes used before and sometimes after grinding to modify the color and flavor 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 colors of cocoa powder can be produced. Complete nib penetration may take an hour. After alkalization the cocoa needs to be dried slowly.
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.
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