A study of chemical Composition, Antioxidants, and volatile compounds in roasted Arabic coffee

Coffea arabica (Rubiaceae) is a basic drink for all Gulf societies, especially Saudi Arabia, it is the main part of the Saudi tradition. This investigation was carried out to track the chemical composition, caffeine content by UV–visible spectrophotometer, acrylamide content by using a gas chromatograph, free radical scavenging capacity by DPPH methods as well as determined the browning index and separated the volatiles compounds using GC–MS for the most common three degree of roasted Arabic coffee; light (180 ± 10 °C; 6.0 ± 1.0 min), medium (180 ± 10 °C; 8.0 ± 1.0 min), and dark (180 ± 10 °C; 10.0 ± 1.0 min). Data revealed that light roasted coffee has the highest significant (p < 0.05) value of moisture content (4.80%), crude protein (13.05%), and lowest value of ether extract (10.39%) and crude fiber (24.24%). The caffeine content was found to be 1.13% in light coffee, which increased to 1.17% in medium coffee, then decreased to 1.08% in dark coffee. The quantity of acrylamide detected in light roasted coffee (0.41 mg/100 g) was the greatest, whereas medium roasted coffee comparatively produced low amounts (0.31 mg/100 g). The light roasted coffee gave the highest antioxidant activity (88.72 mg TE/g), while the dark roasted coffee gave the least activity (78.76 mg TE/g). Browning index increases with roasting time. Hydrocarbons, alcohols, and esters were the most represented in roasted coffee headspace. Silanes and sec-butyl nitrite compounds were absent in the medium roasted headspace. Except for amines, all 11 classes of volatile compounds were present in the headspace of dark roasted coffee.