We investigated the effect of roasting degree on volatile and phenolic compounds of coffee beans (Coffea Arabica L. cv. Catimor). The colour, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity and phenolic acids of the aqueous extracts were studied. For the colour, L and b values were increased with an increase in roasting degree. Increasing roasting degrees led to a decrease in radical-scavenging activity. Maximum radical-scavenging activity was observed for the light-roasted coffee. Chlorogenic acid was the most predominant amongst the ten phenolic acids identified, in green and all roasted beans. Syringic acid, p-coumaric acid, gallic acid and sinapic acid increased with an increase in roasting degree. The volatile compounds were analysed using gas chromatography and mass spectroscopy. Aldehyde was the major volatile compound in green coffee. Our study has demonstrated that light-roasted coffee gave the most desirable quality of roasted coffee with respect to phenolic content and radical-scavenging activities.

Antioxidant activity was highly positively associated with chlorogenic acid content. The content of total sugar (fructose, glucose and sucrose) was found highest in coffee beans grown in 60% shade, with fructose the predominant sugar. Under climatic conditions similar to this experiment, it is advisable that growers provide shade to the coffee crop to reduce heat from direct sunlight and promote yield as well as obtain good quality coffee beans.