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

摘要

The effects of different concentrations of ubiquinol-10 (Q_(10)H2) 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 Q_(10)H2 in the current formulation was determined to be around 0.10 wt % in the system (Q_(10)H2/citral ratio 1:1), which can effectively protect citral from chemical degradation and oxidation. Results suggested, however, that a low concentration of Q_(10)H2 may induce the majority of the ubisemiquinone (Q_(10)~(·-))/ubiquinone (Q_(10)) redox transition, which possibly endowed Q_(10)H2 with pro-oxidant properties. Further increase in Q_(10)H2 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 Q_(10)H2 presented in the system, major citral oxidation off-flavor compounds (p-cresol, a,p-dimethylstyrene, p-methylacetophenone), and some of the lipid degradation products can be inhibited to lower levels. In contrast, ubiquinone-10 (Q_(10)) had a negligible effect on citral's chemical stability and off-flavor generation.