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Roasting is one of the main stages of coffee processing. The kinetics of chemical reactions that occur during roasting, such as Maillard reaction, pyrolysis, and caramelization, are determined by specific conditions such as temperature and time, with little data on the effect of pressure variation. The Maillard Reaction consists of a set of chemical reactions between reducing sugars and amino acids that lead to the formation of aroma, flavor, and color compounds. Caramelization reactions between sugars also contribute to these parameters. The color, generated by different polymers, is a visible indication of the degree of roasting and can be measured instrumentally. Therefore, this work focused on understanding the effect of interactions between temperature, time, and roasting pressure on the coffee color. For this, coffee beans were roasted in a laboratory roaster with heat supply by heating plates and agitated by a straight-blade mechanical stirrer. Two type J mineral insulated thermocouples measured the temperature, and an analog manometer monitored the pressure. The following conditions were used: temperature (190 ° C and 230 ° C); time (10min and 5min); and pressure (760mmHg and 100mmHg). The experiments were carried out following a factorial design 23, with two replicates at the central point. The color was determined by a color meter. The temperature, the time, and the interaction between these factors were statistically significant for color; therefore, time and temperature cannot be studied separately. It was also possible to obtain a mathematical model for determining the color of the grains based on the process conditions in the respective roaster. The model was validated by data comparison and can be used to plan the process conditions to be operated to obtain the desired roast degree and color.

brazilian journal of development

MODELAGEM DAS CONDIÇÕES OPERACIONAIS DE TORREFAÇÃO E ANÁLISE DOS SEUS EFEITOS SOBRE A COR DO CAFÉ / MODELING OF OPERATING ROASTING CONDITIONS AND ANALYSIS OF THEIR EFFECTS ON COFFEE COLOR