Effects of Roasting Conditions on Chemical Composition, Antioxidants, Volatile Compounds and Sensory Qualities in Arabic Coffee

Abstract

In this study, the most popular three degrees of roasted Arabic coffee—light (210 ºC; 20 min), medium (230 ºC; 20 min), and dark (240 ºC; 20 min)—were examined for their chemical composition, caffeine content, acrylamide content, phenolic content, antioxidant potential, browning index, and volatile compound separation using GC–MS. The results showed that light-roasted coffee had the lowest levels of ether extract and crude fibre and the highest levels of moisture content and crude protein, both of which were significant (p < 0.05). The roasting process, particularly the dark roasting, has reduced the amounts of quercetin, kaempferol, caffeine, trigonelline, and hydroxymethylfurfural, with the exception of quercetin, in both green and roasted coffee samples.  Light-roasted coffee had the highest amount of acrylamide (0.47 mg/100 g), while medium-roasted coffee had very low levels (0.38 mg/100 g). The higher the roasting degree, the higher the browning index. The coffee that was light-roasted had the lowest levels of condensed tannins and flavonoid compounds, the highest levels of free total phenolic content, and the lowest levels of DPPH activity. In terms of GC-MS, the dark-roasted coffee included 120 volatile chemicals that were identified and semi-quantified. Overall, this study demonstrated that while intense roasting would decrease the amount of phenolic chemicals in coffee beans, it might preserve or even increase their antioxidant potential. The nutritional value and organoleptic qualities of commercial light-roasted coffee beans are comparatively superior. Our findings may help resolve past disputes and provide useful proof for coffee production in the food sector.