Antioxidant efficacy of extracts produced from pickled and dried mustard in rapeseed and peanut oils

Antioxidant efficacy of 70% ethanol extract (EE), 70% methanol extract (ME), and water extract (WE) produced from pickled and dried mustard (Brassica juncea Coss. var. foliosa Bailey) was evaluated in rapeseed and peanut oils by using the Schaal oven method. The protective effects of aforesaid 3 extracts in stabilizing vegetable oils were tested by measuring their peroxide values, conjugated diene values, and p-anisidine values during storage of 15 d at 60 °C. Results showed that the different solvent extracts produced from pickled and dried mustard, at concentrations of 0.5% and 1.0% (w/w) in vegetable oils, could significantly (P < 0.05) lower the peroxide value, conjugated diene value, and p-anisidine value of oils during storage at 60 °C. However, the extracts at various concentrations showed a less antioxidant effect than butylated hydroxytoluene (BHT) at 200 ppm. The ultraviolet spectra of different extracts exhibited a single maximum absorbance at 268 nm. The qualitative analysis of antioxidants present in the extracts was carried out by reverse phase high performance liquid chromatography (HPLC) using a C18 column. Two phenolic compounds, gallic and protocatechuric acids, were identified. The antioxidant activity of the extracts might be attributed to the presence of these phenolics. These results indicated that the pickled and dried mustard could be used as a potential source of natural antioxidants.

The antioxidant activity of extracts produced from pickled and dried mustard toward rapeseed and peanut oils oxidation and the characterization of active phenolic compounds may be useful in developing natural antioxidants for vegetable oils. Moreover, the extracts could safely be used as potential antioxidant to suppress lipid oxidation in lipid-containing food products.