Fluorescence of oxidizing oil-in-water emulsions (abstract only)

Abstract

Front-face fluorescence spectroscopy was used to characterize modifications of fluorescence spectra of oil-in-water emulsions, stabilized by bovine serum albumin (BSA) or sodium caseinate during aging at 50°C. Commercial sunflower oil or the same oil stripped of tocopherols, were used as the apolar phase of the emulsions. The 3D-fluorescence spectra of the emulsions were characterized by three groups of fluorescent pigments: (i) protein aromatic amino acid residues, mainly tryptophanyl residues (Trp); (ii) pigments initially present in the oils:tocopherol and others; (iii) new fluorescent pigments due to reactions of lipid oxidation products with the proteins. During oxidation of the emulsions, the fluorescence intensities of protein Trp and oil's pigments decreased whereas the new fluorescent pigments were produced. As expected, and in agreement with development of lipid oxidation, the changes were slower for the unstripped than for the stripped oil. The relative fluorescence intensity of protein Trp decreased slightly faster in the caseinate-stabilized emulsions than in the BSA ones. Increases in fluorescence intensity of new pigments showed no difference.