Is oxygen reduction a viable antioxidant strategy for oil-in-water emulsions?

The impact of 0, 40, 58, 79, 93, and 98% total oxygen reduction on lipid oxidation kinetics in a 1.0% fish oil-in-water emulsion (pH 3.0; 32 degrees C) was determined. Atmospheres were modified using nitrogen/oxygen gas blends or high purity nitrogen. Headspace and dissolved oxygen were monitored throughout the study using a non-destructive technique in which fluorescent sensors were fixed in sealed vials. Lipid oxidation, as measured by lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS), was inhibited at oxygen reductions 58%. However, meaningful protection against lipid oxidation was only achieved at oxygen reductions 93%. Potential commercial strategies, nitrogen flushing/sparging, and ascorbic acid, were inefficient at reducing oxygen to levels that could significantly inhibit lipid oxidation. Results suggest that near complete oxygen removal is necessary to protect oxygen-sensitive ingredients, but a need still exists to identify new strategies that sufficiently reduce the oxygen content of emulsions. Practical applications: The practical application of this work is that there is a global demand to remove synthetic additives from food and beverage formulations, and as described in this work, defining the level oxygen reduction that provides meaningful increases in oxidative stability is necessary. Results suggest that the oxidative stability of 1% fish oil-in-water emulsions can be extended by reducing system oxygen by approximate to 58%, but to have a meaningful antioxidant impact greater than approximate to 93% oxygen removal is required. Further investigation into simulated commercial oxygen removal strategies (e.g., nitrogen displacement of oxygen and ascorbic acid) demonstrated that current industrial strategies are lacking and need to be optimized in order to enhance stability against lipid oxidation. In this work, we design and modify a fish oil-in-water emulsion system to have different oxygen concentrations that range from almost complete oxygen removal to atmospheric conditions. The resulting emulsions are characterized over time by non-destructively measuring oxygen concentrations, both in the headspace and dissolved phase, as shown in the figure of two sensor patches inside a sealed glass vial. The impact of oxygen concentrations on lipid oxidation kinetics is measured and represented in the graphed data. Results suggest that near complete oxygen removal is necessary to provide meaningful protection against lipid oxidation in emulsified systems.