Drying kinetics of peeled coffee submitted to different temperatures and relative humidity of the air of drying after partial drying ; Cinética de secagem de café descascado submetido a diferentes temperaturas e umidades relativas do ar de secagem após meia seca

The mathematical modelling is fundamental for the understanding of the related processes the drying, that influences the quality of the coffee drink. The objective of this study was to evaluate the influence of different relative humidity of the drying air after partial drying on drying kinetics of peeled coffees. Coffee fruits were harvested in the cherry stage and processed by wet, resulting in the portion of peeled coffee. Eleven treatments of drying were accomplished, being nine results of the combination of three dry bulb temperatures and three dew point temperatures, more two treatments without the control of the dew point temperatures. The control of the relative humidity by the dew point temperature was made after the grains reached the partial drying. Among the studied models, those of Diffusion Approximation and Modified Midilli were the most adequate for describing the drying process of the first and second part of drying respectively. The effective diffusivity coefficient of water in coffee grains ranged from 0.81 x 10-11 to 1.84 x 10-11 m² .s-1 during the first part of the drying and ranged from 1.49 x 10-11 to 3.29 x 10-11 m² .s-1 during the second part of the drying, increasing significantly with the reduction of the dew point temperature and increase of the dry bulb temperature. ; A modelagem matemática é fundamental para a compreensão dos processos relacionados à secagem, que por sua vez, influencia diretamente a qualidade da bebida do café. Assim, o objetivo deste trabalho foi estudar a influência que diferentes umidades relativas do ar de secagem após meia seca têm sobre a cinética de secagem dos cafés descascados. Os frutos de Coffea arábica L. foram colhidos no estádio de maturação cereja e processados por via úmida, resultando na porção de café descascado. Foram realizados onze tratamentos de secagem, sendo nove resultados da combinação de três temperaturas de bulbo seco e três temperaturas de ponto de orvalho, mais dois tratamentos sem o controle da temperatura de ponto de orvalho. O ...