Antioxidant activity of phenolic compounds in sunflower oil-in-water emulsions containing sodium caseinate and lactose

Abstract

The aim of this work was to study the evolution of oxidation and the efficiency of phenolic antioxidants in sunflower oil-in-water emulsions containing sodium caseinate and lactose (Cas-Lac) or stabilized by Tween-20 (T-20). Two groups of phenolic antioxidants which are structurally similar were tested, i.e. (1) α-tocopherol and its water-soluble analogue, Trolox; and (2) gallic acid and its ester derivatives propyl gallate and dodecyl gallate. Emulsion samples were oxidized at 40°C and the progress of oxidation was followed through quantitation of oxidized triacylglycerol monomers, dimers and oligomers. Results showed that Cas-Lac emulsions were more stable to oxidation than T-20 emulsions. In both types of emulsions, the most protective antioxidants were the compounds of lower polarity, namely, α-tocopherol and dodecyl gallate. It was also found that substantial amounts of α-tocopherol coexisted with significant polymerization, which was indicative of the heterogeneity of oxidation, i.e. differences of oxidation rate in oil droplets.