Roasting process of cocoa beans

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.

Roasting process of cocoa beans

Coffee process of roasting

Green beans smell green earthy, so they must be heat treated in a process called roasting to bring about their truly delightful aroma.

Coffee beans are usually roasted in large batch dryers which spin and heat them evenly at temperatures that reach 550° F. In the USA continuous roasting of beans is the common method, using fluidization of beans in a perforated cylinder with a horizontal airstream.

The process consists of roughly three stages lasting about six minutes altogether: begin roasting, end roasting, quenching. During roasting heat is transferred by contact of the beans with the walls of the roasting apparatus or by hot air or combusted gases.

The bean is warmed intensely to drive off free and bound moisture which constitute about 12% of initial weight. During the roasting process, about 20 percent of the water content of the green beans evaporates and carbon dioxide escaped. They are accompanied by some carbon monoxide and organic volatiles.

The bean’s starch content is converted to sugar. The volatiles oils and acids that gave coffee its tempting aroma and delicious flavor are developed during the roasting process.

The roasting process is terminated at the desired flavor, indicated by the darkness of color.

When the desired degree of roast is reached, the beans have to be cooled down rapidly by water quenching or cold air in order to stop further changes in color, flavor and volume. Normally the product is discharged into an air cooler for rapid cooling to 104° F.
Coffee process of roasting

Coffee roasting

Roasting brings raw, green coffee beans to a state called pyrolysis, which generally occurs at from 400 ° F to 420° F (204 ° C to 216 ° C) and liberates about 150 to 200 BTUs of heat. The beans are roasted to a light color for 3-10 minutes which weight loss 14 – 17%.

At 212° F the coffee beans turn yellow and lose water, from 248° F to 302 ° F the color changes from yellow to light brown and russet, folds in the beans open and release an essential oils, cafeone. At 392° F pyrogenation is reached.

The loss in weight by roasting depended on the kind of the coffee and the manner in which the roasting was done.

During roasting, vapors formed and cell fragments are removed by suction of an exhauster and in larger plants, incinerated.

Until coffee is roasted, its taste remains unknown. The end product is discharged rapidly to cooling sifters or is sprinkled with water in order to avoid over-roasting or burning and aroma loss.

The cooling was then followed by an air suction operation called ‘stoning’ which removed any stones or other hard material that would damage a grinding mill.

By the time coffee finishes roasting, more than 700 identified compounds cumulatively called coffee flavor – exist.

The most obvious change was production of a fragrance, attributed to a mixture do several substance. It was partly due to the volatile oil called caffeol, which was produced at the expense of other substances and partly to the sugars which were caramelized.
Coffee roasting

Roasting

Roasting is often used when preparing succulent meats such as ham roast, crown roast, tenderloins, turkey and rubs.

Roasting is often associated with festive times such as holidays or special occasions.

It is a dry heat method. No water is used, and the meat is not covered, so steam can escape. In principle, roasting meats is a simple procedure. The prepared cut meat is placed in an oven at a selected temperature and it is removed when done.

During roasting a crust is formed on the surface, which preserves the internal part from too sudden or violent a degree of heat and also prevents the draining away of its juice.

Historically, roasting meant cooking meat over an open fire. As time evolved, and the concept developed, meat was impaled onto a spit that turned over the flame.

The Brits perfected this technique in the 18th century one of their culinary claims to fame. Salt added to the surface of meat just before roasting will penetrate the meat only a fraction of an inch during cooking.

The same is true of the flavors of the herbs, spices and aromatics.
Roasting