Cocoa bean roasting process

Roasting is the most important technological operation in cocoa beans processing, and the degree of chemical changes depends on the temperature applied during the process. Roasting is the operation for the development of aroma and flavour of cocoa beans at temperatures of 110°C to 140°C and time range of 20 to 50 min. 

Roasting involves complex chemical transformations, attributed to Maillard reactions, caramelization of sugars, protein degradation, and synthesis of sulfur compounds. 

During roasting, some compounds increase in concentration, the volatile fraction decreases, and new compounds are formed. Moisture loss and chemical reactions suffered by the beans in the roasting process affect the color, volume, mass, shape, bead pop, pH, density, and especially volatile compounds and flavor. 

The selection of process parameters has a decisive influence on the nature of chemical and physical changes occurring in the cocoa beans, which determines the quality of the final products. 

The color is one of the most important physicochemical properties of roasted cocoa beans because it affects the quality of products derived from this commodity. Brown color is preferred to red-violet. This  parameter depends not only on contents of polyphenols and anthocyans and their derivatives but also on the presence of Maillard reactions products and products of starch dextrinization. 

Pyrazines, a by-product of Maillard reaction is one of the character impact compounds that contribute to unique cocoa flavour. 

The precursors of flavour are developed during fermentation and drying of cocoa beans, which include the free amino acid, peptides and reducing sugar, contributing to the development of cocoa specific aroma through Maillard reaction during roasting.

Cocoa bean roasting process

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

Roasting of cocoa beans

Cocoa are taken from their pod and fermented to develop flavor. Cocoa beans must be cleaned before processing to produce a wholesome product with minimal microbiological risks and to remove extraneous materials. Most modern coca factories use continuous roasting ovens of the revolving drum type.

The roasting process results in the development of the favor and aroma of the beans. During roasting the ultimate flavor profile is achieved. It is well known that Millard reactions started during fermentation and drying continue at this stage of processing.

There are several methods, which includes whole bean, nib and chocolate liquor roasting.

Roasting can take anywhere from 15 min to 2 hour. Whichever roasting method is used, the nibs are separated from the shell. Depending upon the degree of roast, the final nib moisture ranges from 1.5% - 3%. Federal standards allow no more than 1.75 percent in the nib potion used for chocolate production.

The intensity of the roasting determines the amount of volatile components formed, as well as the removal of volatile components like esters and low molecular acids.

After roasting, the nibs are ground to a liquid state, which is called chocolate liquor. The heat and friction from the grinding process will rupture the cell walls of the nibs to release the valuable cocoa butter.
Roasting of cocoa beans

Cocoa Powder

Cocoa Powder
Cocoa powder is a valuable flavoring material in baked goods and desserts as well as the basis of hot chocolate drinks. It is produced by finely milling the press-cake after partial removal butter from the roasted nibs by hydraulic pressure. This removes most of the fats but still leaves about 22% in the press-cakes. The flavor is little; affected by this process and in consequence, the cocoa notes are more concentrated in the powder than in the chocolate liquor.

The commercial powder varies in color and flavor, dependent upon the quality of the beans used the degree of roasting and the precise method of processing. A good quality cocoa powder has the following characteristics:

• PH: 5.6 to 7.1 dependent upon whether or not the cocoa beans were processed with alkali.

• Fat: about 24% and not less than 22%.

• Moisture: 3.4% but many be as high as 7%

Cocoa Powder

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