Stabilisation of omega-3 oils in food emulsion systems

Lipid oxidation can lower the nutritional value and quality of foods, and form toxic compounds, off-flavours and off-odours; its control in food systems rich in unstable omega-3 oils is essential. Sunflower oil, camelina oil and a camelina:fish oil blend (72:28) emulsified using sodium caseinate (NaCas) had lower lipid hydroperoxides and p-Anisidine values (p- Avs) than their corresponding bulk oils (P<0.05). Oxidation also decreased as NaCas concentration and microfluidisation pressure increased (P<0.05). Increasing storage temperature of emulsions (5-60 °C) resulted in an apparent decrease in detectable lipid oxidation products on storage. Omega-3 rich O/W emulsions (50 % oil), were incorporated into an outer oil phase of table spreads, to produce multiple emulsion systems (O/W/O), with the aim of further improving oxidative stability. Lipid hydroperoxides of the spreads increased over storage at 5 ºC, whereas p-Avs remained low (P<0.05). The continuous phase of the spreads appeared to be the phase most affecting primary oxidation product formation, irrespective of whether an omega-3 rich inner phase was present, indicating a protective effect by the double emulsion. Oxidative stability of omega-3 enriched fat spreads (O/W/O emulsions) using conventional lipid oxidation methods (lipid hydroperoxide and p-Anisidine values), was compared to volatile analysis using SPME-GC/MS and sensory evaluation. Results from sensory evaluation, lipid hydroperoxide analysis and volatile analysis were comparable, whereas p-Anisidine values were less consistent. The effectiveness of fat soluble (α-Tocopherol) and water soluble (green tea extract) antioxidants on the oxidation rate of sensitive ω-3 rich oils, O/W emulsions and O/W/O emulsions (fat spreads) were examined. Emulsions containing α-Tocopherol had the highest lipid hydroperoxides, while emulsions containing green tea extract had the lowest (P<0.05). p-Avs were not affected by anti-oxidant addition (P>0.05). O/W emulsions (camelina/sunflower) were spray-dried to yield powders containing 71.7-85.6 % oil. Emulsification and microencapsulation significantly improved oxidative stability (particularly in camelina oil).