Volatile composition of sunflower oil-in-water emulsions during initial lipid oxidation: Influence of pH

The formation of odor active compounds resulting from initial lipid oxidati on in sunflower oil-in-water emulsions was examined during storage at 60 de grees C. The emulsions differed in initial pH, that is, pH 3 and 6. The vol atile compounds were isolated under mouth conditions and were analyzed by g as chromatography/sniffing port analysis. The lipid oxidation rate was foll owed by the formation of conjugated hydroperoxide dienes and headspace hexa nal. The initial pH affected the lipid oxidation rate in the emulsions: the formation of conjugated diene hydroperoxides and the hexanal concentration in the static headspace were increased at pH 6. Pentanal, hexanal, 3-penta nol, and 1-octen-3-one showed odor activity in the emulsions after 6 days o f storage, for both pH 3 and 6. Larger amounts of odor active compounds wer e released from the pH 6 emulsion with extended storage. It was shown that this increased release at pH 6 was not due to increased volatility because an increase in pH diminished the static headspace concentrations of added c ompounds in emulsions.