Effect of electroreduction and heat treatments on oxidative degradation of a dairy beverage enriched with polyunsaturated fatty acids

A dairy beverage (pH 6.7) containing 3.5% milk protein was supplemented with linseed oil, β-carotene and iron (as FeSO4) before being pasteurized or sterilized. Electroreduction was applied prior to heat treatment and compared to vacuum degassing for prevention of oxidative degradation. Electroreduction decreased dissolved oxygen concentration (Δ = 5.5 ppm) and redox potential (Δ = 519 mV), resulting in a decreased non-enzymatic browning reactions during storage of the pasteurized beverages and reduced lipid oxidation after sterilization. Heat treatments also reduced the redox potential, sterilization being more effective than pasteurization. However, the redox potential after electroreduction did not remain constant as it increased during storage, likely reflecting the low poising capacity of the beverages. Protection against photo-oxidative degradation of unsaturated fatty acids and β-carotene was more effective in sterilized beverages than in pasteurized beverages. The electroreduced samples showed resistance to photo-oxidative stress similar to that of the degassed or control beverages.