Effect of natural and synthetic antioxidants on oxidative stability of FAMEs obtained from hevea brasiliensis

Abstract

Biodiesel (fatty acid alkyl esters), an alternate to fossil fuel, has the tendency of autoxidation and hence requires antioxidants for long term storage. The influence of synthetic and natural antioxidants on the oxidative stability was analysed for fresh FAMEs (fatty acid methyl esters) obtained from hevea brasiliensis at 140 °C. Higher activity was observed for synthetic antioxidants following the order of GA>BHT>DTBP>Q>GT-M>PH-M>GT-C, whereas the oxidative stability of stored FAMEs samples measured at 110 °C reveals a nearly inverse trend. Storage stability was tested for the FAMEs obtained from hevea brasiliensis stored at 30 °C, after addition of synthetic and natural antioxidants—butylated hydroxytoluene (BHT), 2,6-di-tert-butylphenol (DTBP), quercetin (Q), gallic acid (GA), methanol extracts from green tea (GT-M), pomegranate hull (PH-M), and chloroform extract of green tea (GT-C). Antioxidant activities above 1500 ppm was in the order of DTBP>BHT>GA>GT-C>GT-M>Q>PH-M. Synthetic antioxidants have been found more efficient to improve the storage stability of FAMEs obtained from hevea brasiliensis. DTBP in particular has the highest protection factor.