Quantitative Spatiotemporal Mapping of Lipid and Protein Oxidation in Mayonnaise

Abstract

Lipid oxidation in food emulsions is mediated by emulsifiers in the water phase and at the oil–water interface. To unravel the physico-chemical mechanisms and to obtain local lipid and protein oxidation rates, we used confocal laser scanning microscopy (CLSM), thereby monitoring changes in both the fluorescence emission of a lipophilic dye BODIPY 665/676 and protein auto-fluorescence. Our data show that the removal of lipid-soluble antioxidants from mayonnaises promotes lipid oxidation within oil droplets as well as protein oxidation at the oil–water interface. Furthermore, we demonstrate that ascorbic acid acts as either a lipid antioxidant or pro-oxidant depending on the presence of lipid-soluble antioxidants. The effects of antioxidant formulation on local lipid and protein oxidation rates were all statistically significant (p < 0.0001). The observed protein oxidation at the oil–water interface was spatially heterogeneous, which is in line with the heterogeneous distribution of lipoprotein granules from the egg yolk used for emulsification. The impact of the droplet size on local lipid and protein oxidation rates was significant (p < 0.0001) but minor compared to the effects of ascorbic acid addition and lipid-soluble antioxidant depletion. The presented results demonstrate that CLSM can be applied for unraveling the roles of colloidal structure and transport in mediating lipid oxidation in complex food emulsions.

Effect of Nonprotein Components for Lipid Oxidation in Emulsions Stabilized by Plant Protein Extracts

“…Next to non-protein components, the initial level of protein oxidation was positively correlated with lipid oxidation in emulsions ( r = 0.91; p < 0.05 for hydroperoxides). Radical-mediated protein and lipid oxidation can mutually promote each other. ,− Therefore, it may be expected that an initial level of protein oxidation, as a result of the protein fractionation process used (i.e., defatting and wet processing), would be a driver for subsequent lipid oxidation in emulsions formulated with those ingredients, although systematic experimental evidence on this matter is still missing . The protein-bound carbonyl content in the fresh emulsions (between 2.94 and 7.01 μmol/g soluble protein) was consistent with values from literature for commercial plant protein ingredients (∼3–20 mmol/kg), , which clearly points to an aspect of protein materials that is generally overlooked, but that could turn out to be highly relevant for their use.…”

Chemical Stability of Ascorbic Acid Integrated into Commercial Products: A Review on Bioactivity and Delivery Technology

“…In mayonnaise, the added ascorbic acid works as a lipid antioxidant or pro-oxidant depending on the presence or absence of the fat-soluble antioxidant vitamin E. In the system containing vitamin E, the synergistically antioxidant effect of these two vitamins is stronger than the pro-oxidant effect of ascorbic acid. Without the addition of vitamin E, the hydrogen peroxide at the interface of the oil droplets promotes the lipid oxidation of lipoprotein particles in the mayonnaise, which in turn induces the oxidation of apolipoproteins and produces volatile odors [ 40 ]. In addition, dehydroascorbic acid may irreversibly degrade and produce highly reactive carbonyl intermediates, which can induce glycosylation of proteins.…”

Multi-scale imaging of protein oxidation in mayonnaise

“…Upon oxidation of LDLs, fluorescence emission increases in the visible region due to reactions between lipid peroxidation products such as aldehyde with amino groups (Koller et al, 1986;Schuh et al, 1978). We previously assessed protein oxidation in mayonnaise via autofluorescence using 488 nm excitation and detection in the 500-560 nm range (Yang et al, 2020). To confirm the decrease of FL in the UV region and the increase in longer wavelength, we compared the autofluorescence spectrum after excitation at 300 nm, 360 nm, and 405 nm (see Supplementary Fig.…”