Textural changes of coffee beans as affected by roasting conditions

During the roasting process, cowee beans change their textural properties, losing strength and toughness and becoming progressively more brittle, owing to chemical, physical and structural modixcations. The aim of this paper is to evaluate the factors~such as density and moisture~awecting the mechanical properties of cowee beans roasted at 170, 200 3C and under so-called high yield conditions. To distinguish the ewects due to roasting (where both density and moisture changes occur) from those due to the water removal alone, heat treatments on cowee bean samples at dehydration temperatures (90}105 3C) have been also carried out. Results showed that the typical brittleness of roasted and high yield cowee beans seems to be related both to the water loss and to the change of tissue structure owing to the pyrolysis phenomena and to the decrease of density. In fact, even if dried and roasted cowee beans showed, at similar moisture content, a reduced and weak signixcant diwerence in the resistance to fracture and in toughness, roasting caused a decrease of the deformability, the index of a brittle and fragile texture.