Effect of roasting on the total polyphenol content and antioxidant activity of sesame (Sesamum indicum L.) seeds grown in Ethiopia

Abstract

Consumers prioritize safe and high-quality foods, underscoring the importance of ensuring the quality of agricultural products to meet their expectations. Sesame (Sesamum indicum L.) is the most widely grown food crops, cultivated in different cultivars and types throughout the world. It is the second most valuable crop next to coffee in Ethiopia's foreign exchange earnings. The present study aimed to determine the total phenolic content and antioxidant activity of raw and roasted sesame seeds from seven major sesame-producing areas in Ethiopia. The total phenolic and flavonoid contents of raw seeds ranged from 67 to 154 mg GAE/100 g DW and 19–43 mg CE/100 g DW, with DPPH scavenging activity between 0.55 and 0.85 mg AAE/g. Conversely, roasted seeds had average phenolic and flavonoid levels, as well as antioxidant activity, averaging 56–97 mg GAE/100 g DW, 14–21 mg CE/100 g DW, and 0.63–1.04 AAE/g, respectively. Significant differences (p < 0.05) were observed between the raw and roasted seeds in these parameters. The roasting process led to a decline in polyphenol and flavonoid contents, likely due to heat-induced degradation and/or alteration of these compounds. However, the roasted seeds exhibited enhanced antioxidant properties, probably ascribed to the formation of new substances having antioxidant activities. The study suggests further investigation into optimal roasting conditions to minimize polyphenol loss.

Keywords

• Antioxidant activity
• Ethiopia
• Flavonoids
• Polyphenols
• Roasting
• Sesamum indicum