Effect of Heating Process of Ginger on the Concentrations of Major Compound and Antioxidant Capacity

Abstract

Ginger is a spicy vegetable with an antioxidant capacity. 6-Gingerol and 6-shogaol are thought to be the major compounds contributing to its antioxidant activity and their content changes during the heating process. We investigated changes in 6-gingerol and 6-shogaol concentrations using LC-UV and changes in antioxidant capacity using ESR during the heating process. The effects of four cooking processes, namely microwave heating, roasting, boiling, and steaming of ginger, were evaluated. The separation of 6-gingerol and 6-shogaol was achieved using an ODS column with a detection wavelength set at 228 nm for the LC-UV determination. The ESR measurement evaluated antioxidant activity as radical scavenging activity against OH radicals and O₂⁻ radicals. In the boiled and steamed processes, 6-gingerol decreased and 6-shogaol increased. Moreover, the study showed that the conversion of 6-gingerol to 6-shogaol occurred following heating. In addition, all the ginger samples, including a non-heated sample, showed strong O₂⁻ radical scavenging activity. These results suggest that ginger exhibits antioxidant activity by scavenging O₂⁻ radicals more than OH radicals.