Effects of selected herb extracts on iron-catalyzed lipid oxidation in soybean oil-in-water emulsion.

Effect of herb extracts on the oil oxidation of an oil-in-water emulsion containing iron was studied. The emulsion comprised tocopherol-stripped soybean oil (40 g), citrate buffer (60 g, pH 4.0), xanthan gum (35mg), and FeSO4 (0.5mg) with 80% ethanol extracts of rosemary (Rosmarinus officinalis), basil (Ocimum basilicum), peppermint (Mentha piperita), thyme (Thymus vulgaris), or oregano (Origanum vulgare). Hydroperoxide contents and p-anisidine values were significantly (p<0.05) lower in the emulsions with the added herb extracts compared with the control emulsions. The antioxidant activity of the basil and peppermint extracts containing higher proportions of rosmarinic acid was significantly higher (p<0.05) than that of the other herb extracts, but the polyphenol degradation rate was not significantly different. The antioxidant activity of the basil and peppermint extracts showed concentration-dependence within 400 mg/kg. This study suggests that the oxidative stability of oil-inwater emulsion containing iron can be improved by addition of basil or peppermint extract.