Changes during roasting process

In pre-roasting the cocoa beans are quickly heated with hot air or infrared radiant heaters to separate shells from ’nibs’, or bean meat. Beans are roasted at temperature between 100 and 150° C for between 20 to 40 minutes.

During the roasting of the fermented and dried beans several physical and chemical changes take place, which include the following:
*The bean losses moisture to about 2% final content
*The shell is loosened
*The nib (cotyledon) becomes more friable and generally darkens in color
*Sucrose hydrolysis which occurs during fermentation of the beans provides the reducing sugar pool important for aroma formation during roasting process.
*There is some degradation of the amino acids and proteins are partly denatured
*There is a loss of volatile acids and other substances that contribute to acidify and bitterness
*Additional reduction in the number of microorganisms present in the beans

The degree of change is related to the tine and temperature of roasting and to the rate of moisture loss during the process. Roasting conditions vary greatly according to the machine and product required.
Changes during roasting process

Cocoa beans infestation

Once they have been dried, cocoa beans are quite stable and will not deteriorate for several years, provided they are kept under good conditions. These should include an absence of the various insect pests that feed on cocoa beans. 

Cocoa beans may be infested with insects which have not penetrated the beans and whose presence is not revealed by the cut test which is employed for grading purposes. Such insects may subsequently enter beans or they may be involved in cross infestation of other shipments. 

Cocoa beans have to be fumigated more than once to control insects: irradiation could be applied at the terminal end before shipment. Care should be taken to avoid cocoa beans becoming infested in ships and stores from other commodities or with insects remaining from previous shipments. 

Properly prepared cocoa stored in clean, pest free areas will not become infested. Control measures need to be applied as required to the structure of the tore or ship. 

In store infestation can be minimized by good hygiene measures and when necessary the application of pest control. On the arrival at the factory, the beans are usually put through large fumigation chambers and treated with methyl bromide to ensure that no infested beans arrive in the production areas. 

Cocoa beans infestation

Composition of Cocoa Beans

Composition of Cocoa Beans
The general composition of cocoa beans from various sources is similar.

With properly fermented mature beans the variations is relatively small but immature, badly fermented and sometimes intermediate beans have higher shell and lower cocoa butter contents.

The available nib content and hence the cocoa butter, is the factor that should be used to compare the real values of different consignments of beans.

The cleanliness of the outer shell affects the ash content and the microbial counts.

The shell is virtually a waste material as far as the manufacture of cocoa and chocolate is concerned.

Cocoa butter, the natural fat of the nib, is the most costly constituent, although at times powdered cocoa has attained a high value, especially for the manufacture of coatings.

The quality of cocoa beans is determined by the “cut test”, together with flavor of the chocolate made from the beans.

The alkaloid constituents of the cocoa beans, theobromine and caffeine, have been subjects of considerable publicity of recent years because of their supposed connection with migraine, hypertension, and other health problems.
Composition of Cocoa Beans

Fermentation: Chemical Changes in Pulp

Fermentation: Chemical Changes in Pulp
In the process of fermentation the heaps or boxes, the pulp adhering to the beans provides a medium at the correct temperature and pH, not only to liquefy the pulp, but to create the reactions within the cotyledon so vital to the production of good chocolate flavors.

The pulp is composed of approximately 85% of water and 11 percent sugars with small amounts of citric acid, pentosans and proteins.

During the first two days of fermentation, the sugars are broken down to about 2 percent, forming small amounts of ethyl alcohol and lactic acid and the temperature rises to about 45 degree C.

For the remaining period of fermentation, the temperature is maintained between 45 and 50 degree C and the quantity of beans must be sufficient to avoid heat loss. The pH rises from 3.5 initially to 4.5 then to 5.0, and the presence of oxygen during turning results in the formation of acetic acid.

The cotyledons absorb some of the acetic acid, and they also attain a pH of about 5.0.

If fermentation is extended beyond five or six days, spoilage organisms take over, with a detrimental effect on the final flavor of the beans, residual acidity due to acetic acid is a problem with beans from some sources, such as Malaysia and New Guinea.
Fermentation: Chemical Changes in Pulp

Fermentation and Drying Process

Fermentation and Drying Process
The correct fermentation and drying process of cacao are of vital importance as 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 retarded, molds develop and these also impart very unpleasant flavors even if fermentation has been carried out correctly.

The chemical processes involved are not entirely fermenting reactions and the changes that occur in the combined processes of fermentation and drying are sometimes referred to as curing.

After the pods are cut form the trees, the beans with the adhering pulp are removed and transferred to heaps boxes or baskets for fermentation to take place.

Small farmers tend to use the heap method whereas the box method is employed in larger plantations, and is also used on a smaller scale in South America and the West Indies. In Nigeria a basket method has been used, with the baskets lined with leaves.

Fermentation lasts from five to six days. Forastero beans take rather longer than Criollo and during the first day, the adhering pulp becomes liquid and drains away, with the temperature rising steadily.

By the third day, the mass of beans will have fairly evenly heated to 45 degree C and will remain between this temperature and about 50 degree C until fermentation is complete.
Fermentation and Drying Process

The Cocoa Plant

The Cocoa Plant
Botanically, the ‘cacao’ refers to the tree and its fruit (pods and seeds). Cocoa describes the bulk commercial dried fermented beans, as well as the powder produced from the beans.

The tree can only be cultivated within fairly narrow limits of altitude, latitude and humidity. The cultivation of 75% of the world’s cocoa lies within eight degrees of either side of the equator, with exceptions in some areas to about 18 degrees north or south. The optimum growing temperature may fall to lower levels, but then lower yields and damage to the trees are likely.

Rainfall is preferably between 1,500 and 2,000mm per year. Thus a hot, moist climate favors growth. Relative humidity under these conditions will be 70 to 80 percent during the day, increasing to the saturation point at night. Trees grow mostly in the lower altitudes and it is exceptional for them to flourish above 3,000 ft.

The cacao tree will grow to a height of 20 to 30 ft and requires some shade from larger forest trees. From the time the seedling reaches a height of 3 to 5 ft it throws out three to five fan branches, and later vertical “chupons” from points below “jorquettes” where branches fork. This pattern of growth is repeated until the height of maturity is reached.

The flowers are about half an inch in diameter and are formed in small groups on the trunks and flower main branches of the trees. They are bisexual, have no nectar or perfume, and the pollen is too sticky to be dispersed by the wind. It is found that the main agent of pollination is a small midge.

Many flowers are produced but only a small number become pollinated and develop into pods. These pods mature in five to six months during which many wilt and drop off, and this constitutes a further thinning process.

The pod is botanically, a “drupe” and stains a length of 6 to 10 in, by 3 to 4 in. diameter. It normally contains twenty to forty seeds surrounded by a mucilaginous pulp when the pod is ripe. It is an unusual fact that the ripe pods do not open and scatter the seed, not do the pod drop off and rot, and the seeds have no dormancy when removed from the pod. In uncultivated areas the seed is spread by small mammals such as monkeys and squirrels, which open the pods, such off the sweet pulp, and spit out the seeds.
The Cocoa Plant

From raw cocoa to cocoa flavor

From raw cocoa to cocoa flavor
Raw cocoa nibs do not posses the distinctive aroma and flavor of cocoa, this being developed only as a result of the fermentation and roasting processes. Both of these have been shown to be necessary for the production of the characteristics profile. The optimum conditions necessary to produce a high quality product are still a matter of expert judgment.

There are 3 stages or process to convert into flavor
Fermentation

Drying

Roasting

Fermentation, during which the flavor precursors are formed. The proteins present in the nibs are degraded and the level of free amino acids rises: sucrose is inverted to fructose and glucose which in turn are oxidized to alcohol and various acids; some theobromine and tannins are lost

Drying, during which the moisture content is reduced to about 8% with a loss of volatile acids and a consequent rise in PH.

Roasting, during which the precursors are converted into aromatic compounds, the qualitative and quantitative nature of which determines the characteristics profile of the roasted beans.

Cocoa beans are the source of three other important materials;
Cocoa butter: a mixture of glycerides which are present from 52-56% in the nib.

Theobromine: an alkaloid related to caffeine but having very little stimulant effect

Cacao purple: an astringent coloring matter formed in the fermenting bean.
From raw cocoa to cocoa flavor