Efficacy of gossypol as an antioxidant additive in biodiesel

The efficacy of gossypol as an antioxidant additive in fatty acid methyl esters (FAMEs) prepared from soybean oil (SME), waste cooking oil (WCME) and technical grade methyl oleate (MO) was investigated. Gossypol is a naturally occurring polyphenolic aldehyde with antioxidant properties isolated from cottonseed that is toxic to humans and animals. At treatment levels of 250 and 500 ppm, gossypol exhibited statistically significant improvements in the induction periods (IPs; EN 14112) of SME, WCME and MO. Efficacy was most pronounced in SME, which was due to its higher concentration of endogenous tocopherols (757 ppm) versus WCME (60 ppm) and MO (0 ppm). A comparison of antioxidant efficacy was made with butylated hydroxytoluene (BHT) and γ-tocopherol. For FAMEs with low concentrations of endogenous tocopherols (WCME and MO), γ-tocopherol exhibited the greatest efficacy, although treatments employing BHT and gossypol also yielded statistically significant improvements to oxidative stability. In summary, gossypol was effective as an exogenous antioxidant for FAMEs investigated herein. In particular, FAMEs containing a comparatively high percentage of endogenous tocopherols were especially suited to gossypol as an antioxidant additive.

► Gossypol is a naturally occurring polyphenolic isolated from cottonseed.
► Gossypol is toxic and must be removed from cottonseed before food applications.
► Gossypol improved the oxidative stability of biodiesel.
► The activity of gossypol was similar to BHT and gamma-tocopherol.