The antioxidant activity of curcumin and b-carotene was studied as a method to control the oxidative
process of methyl soybean biodiesel during a 180-day storage period. Initially, the antioxidant activity
of curcumin and b-carotene against radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) was tested. Curcumin
reduced the concentration of DPPH by 90% whereas b-carotene reduced it by 15%. The antioxidant activity
was determined through both the Rancimat and Petro-OXY methods. Results obtained from the two
methods were consistent. They showed that curcumin increased the induction period of biodiesel by 83%,
indicating the potential use of this antioxidant on an industrial scale. However, the study showed that
b-carotene acts as a pro-oxidant, reducing the induction period of biodiesel when subjected to the
Rancimat and Petro-OXY tests.