The effect of roasting method on headspace composition of robusta coffee bean aroma

Robusta coffee beans were roasted by three methods, i.e. convectively at 230 °C, by microwaves at 700 W, and by the coupled convective–microwave (CMR) method (the simultaneous convective heating at 230 °C and microwaving at 700 W) for 590, 670, and 370 s, respectively. The ultimate temperature of roasted beans was 238, 207, and 228 °C, respectively. Volatile compounds were determined in the headspace by GC-SPME both in samples of roasted coffee and in green beans to find effects of roasting methods on their formation and retention. Eighty-two and 148 odorants were identified in green and roasted coffee, respectively. The highest contents of the latter were found in coffee roasted by the coupled method because both the relatively short time of roasting and moderately high final temperature of beans favored retention of volatile aroma compounds. Because of these reasons, the contents of odorants were the lowest in convectively roasted coffee.