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Changes in physical and chemical characteristics of coffee beans after thermal processing by roasting

This work investigates the two most popular coffee cultivars (Coffea arabica and Coffea canephora) exposed to thermal processing of conduction drying by roasting at temperatures of 170 and 190 °C for 15 and 30 minutes air velocity in front of the coffee bean layer was 1 m/s. In order to determine how roasting temperature and time influence the characteristics of beans of both cultivars, physical properties (length, width, thickness and sphericity) and chemical properties (moisture, ash, and fat) of beans were stady before and after toasting. The tests were performed according to the standard ISO methods, and for roasting a laboratory roaster with temperature and air rate control was used. The obtained results corroborate that the dimension and sphericity of coffee bean increase in both cultivars, regardless of the roasting time and temperature. Also, moisture and oil contents significantly diminish in relation to temperature and time, while ash content is not influenced by roasting. All data were statistically analysed.

chemical characteristics, coffee beans, physical characteristics, roasting

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