PHYSICAL CHANGES DURING COFFEE ROASTING IN ROTARY CONDUCTION-TYPE HEATING UNITS

摘要

Coffee beans were roasted in a rotary conduction-type-heating unit under constant heating surface or product temperatures ranging from 200 to 240C or 170 to 210C, respectively. The roasting duration was varied from 0 to 70 min through intermittent sampling of coffee beans at selected intervals. There were marked changes in physical conditions of coffee beans during roasting. The specific gravity, bulk density, susceptibility to breakage, and color lightness index L changed from 1.2 to 0.5, 0.7 to 0.3 g/cm~3, 20 to 100, and 50 to 12, respectively.