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Effect of Ubiquinol-10 on Citral Stability and Off-Flavor Formation in Oil-in-Water (O/W) Nanoemulsions

Zhao, Qin, Ho, Chi-Tang, Huang, Qingrong
Journal of agricultural and food chemistry 2013 v.61 no.31 pp. 7462-7469
chemical degradation, citral, free radicals, gas chromatography, microextraction, nanoemulsions, off flavors, oxidation, p-cresol
The effects of different concentrations of ubiquinol-10 (Q₁₀H₂) on citral’s stability were systematically investigated and compared in citral-loaded oil-in-water (O/W) nanoemulsions. Solid phase microextraction gas chromatography (SPME-GC) was employed to monitor the degradation of citral and the formation of off-flavor compounds throughout storage at 25 and 45 °C. The optimum concentration of Q₁₀H₂ in the current formulation was determined to be around 0.10 wt % in the system (Q₁₀H₂/citral ratio 1:1), which can effectively protect citral from chemical degradation and oxidation. Results suggested, however, that a low concentration of Q₁₀H₂ may induce the majority of the ubisemiquinone (Q₁₀•–)/ubiquinone (Q₁₀) redox transition, which possibly endowed Q₁₀H₂ with pro-oxidant properties. Further increase in Q₁₀H₂ concentration beyond a certain value also hindered its effect due to the complex properties of radicals involved and the overall environment encountered. With appropriate concentrations of Q₁₀H₂ presented in the system, major citral oxidation off-flavor compounds (p-cresol, α,p-dimethylstyrene, p-methylacetophenone), and some of the lipid degradation products can be inhibited to lower levels. In contrast, ubiquinone-10 (Q₁₀) had a negligible effect on citral’s chemical stability and off-flavor generation.