Effect of evening primrose extracts on oxidative stability of sunflower and rapeseed oils

Antioxidative activities of evening primrose seed meal extracts in sunflower and rapeseed oils were compared with that of commercially used antioxidants, namely butylated hydroxytoluene (BHT), ascorbylpalmitate as well as Grindox-118. The study was carried out under Schaal oven conditions at 60 degreesC and the weight gain was followed up by p-anisidine value measurement following the oxidation. An Oxidograph apparatus monitored the oxidation of oils at 110 degreesC. Among the examined extracts, the ethyl acetate extract (0.2%), containing only 87 mg/g of total phenolics, exhibited a stronger antioxidant activity than BHT (0.01%) and effectively stabilised both oils. A strong antioxidative effect was also noted for the ethanol-ethyl acetate extract (168 mg/g of total phenolics). The study showed that addition of ethyl acetate and ethanol-ethyl acetate extracts could extend the sunflower and rapeseed oils shelf-life by protecting oils from further decomposition that naturally occurs during thermal treatments.