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

Antioxidative activities of evening primrose seed meal extracts in sunflowe r and rapeseed oils were compared with that of commercially used antioxidan ts, namely butylated hydroxytoluene (BHT), ascorbylpalmitate as well as Gri ndox-118. The study was carried out under Schaal oven conditions at 60 degr eesC and the weight gain was followed up by p-anisidine value measurement f ollowing the oxidation. An Oxidograph apparatus monitored the oxidation of oils at 110 degreesC. Among the examined extracts, the ethyl acetate extrac t (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 e thyl 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.