Thermal properties of Conilon coffee fruits

The specific heat, thermal conductivity and diffusivity of coffee fruits (Coffea Canephora) from the clone 32 of clonal variety EMCAPA 8131 were determined for moisture content ranging from 0.134 to 1.454 d.b. for unripe fruits and from 0.133 to 1.634 d.b. for ripe fruits (cherries). The specific heat was determined by the method of mixtures and the values from 1.442 to 3.298 kJ kg -1 K -1 and 1.431 to 3.615 kJ kg -1 K -1 were obtained for the unripe and cherry fruits, respectively and increased linearly with increasing moisture content. The thermal conductivity was measured by transient method with linear source of heat and its behaviour is similar to that of specific heat, ranging from 0.117 to 0.204 W m -1 K -1 and 0.108 to 0.216 W m -1 K -1 for unripe and cherry coffee, respectively. The thermal diffusivity values calculated by the indirect method from the results of specific heat and thermal conductivity ranged from 1.671 × 10 -7 to 1.044 × 10 -7 m 2 s -1 and 1.594 × 10 -7 to 1.047 × 10 -7 m 2 s -1 for unripe and cherry coffees, showing a decreasing linear ratio as moisture content increased.