Yang Suyeon, Verhoeff Aletta A, Merkx Donny W H, van Duynhoven John P M, Hohlbein Johannes
Laboratory of Biophysics, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
Unilever Global Foods Innovation Centre, Plantage 14, 6708 WJ Wageningen, The Netherlands.
Antioxidants (Basel). 2020 Dec 15;9(12):1278. doi: 10.3390/antiox9121278.
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 ( < 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 ( < 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.
食品乳液中的脂质氧化由水相和油水界面处的乳化剂介导。为了揭示其物理化学机制并获得局部脂质和蛋白质氧化速率，我们使用了共聚焦激光扫描显微镜（CLSM），从而监测亲脂性染料BODIPY 665/676的荧光发射和蛋白质自发荧光的变化。我们的数据表明，从蛋黄酱中去除脂溶性抗氧化剂会促进油滴内的脂质氧化以及油水界面处的蛋白质氧化。此外，我们证明，根据脂溶性抗氧化剂的存在情况，抗坏血酸既可以作为脂质抗氧化剂，也可以作为促氧化剂。抗氧化剂配方对局部脂质和蛋白质氧化速率的影响均具有统计学意义（<0.0001）。在油水界面观察到的蛋白质氧化在空间上是不均匀的，这与用于乳化的蛋黄中脂蛋白颗粒的不均匀分布一致。液滴大小对局部脂质和蛋白质氧化速率的影响显著（<0.0001），但与添加抗坏血酸和消耗脂溶性抗氧化剂的影响相比要小。所呈现的结果表明，CLSM可用于揭示胶体结构和传输在介导复杂食品乳液中脂质氧化中的作用。
