Effect of superheated steam roasting on radical scavenging activity and phenolic content of robusta coffee beans

Abstract

Robusta coffee is one of the coffee species grown in Malaysia. However, there is little research conducted on Robusta coffee beans as Arabica coffee is more popular among the consumers. Coffee is a rich source of antioxidants, therefore research on antioxidant properties of Robusta coffee beans is important to explore its market value. Nowadays, most of coffee analysis is on conventional roasted coffee which reduces their antioxidant properties. In this study, Robusta coffee beans (Coffea canephora) were subjected to superheated steam roasting at 200, 220 and 240 °C for 20-40 min to obtain light, medium and dark roast. The effect of different roasting temperature and time on the total phenolic content (TPC) and radical scavenging activity (RSA) of Robusta coffee bean was investigated. Total phenolic content of coffee brews decreased with the increase of roasting degree due to the degradation of phenolic compounds. The highest phenolic content was found at 220 °C for 20 min. Meanwhile, brews extracted from light roasted coffee and medium roasted at 220 °C for 20 min showed a maximum scavenging activity than those from green coffee. Brews from dark roasted coffee showed lowest radical scavenging activity and total phenol content. Hence, based on the results from this study, the best superheated steam roasting condition is at 220 °C for 20 min (medium roast) to achieve a maximum antioxidant activity and highest phenolic content.