“Oxidative stability of O/W and W/O/W emulsions: effect of lipid composition and antioxidant polarity”

The effect of storage temperature (65°C, 48 hours) on the oxidative stability of a food-grade water-in-oil-in-water (W/O/W) emulsion was studied by comparison with an oil-in-water (O/W) emulsion. The emulsions were prepared with linseed oil or olive oil, and in each case, two antioxidants were evaluated, an aqueous Melissa lyophilized extract and BHA. Emulsions were characterized using brightfield light microscopy and the oxidation was monitored by measuring the lipid hydroperoxides, thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and trienes (CT), alpha-tocopherol and Lipophilic Oxygen Radical Absorbance Capacity (L-ORACFL) Assay. A great stability of olive oil emulsions was observed, without noticing differences between antioxidants or type of emulsion. This behaviour was not observed in linseed oil emulsions. In this case the lipophilic antioxidant (BHA) seemed to be more efficient delaying the lipid oxidation in W/O/W emulsions than the water Melissa extract while the opposite occurs in the O/W emulsion. The type of antioxidant is a key factor in controlling oxidation in W/O/W and O/W emulsions which are prepared with highly polyunsaturated oils, but not in the case of highly monounsaturated ones.