Spectroscopy & Imaging, Unilever Research and Development Vlaardingen, Vlaardingen, the Netherlands.
Laboratory of Food Chemistry, Wageningen University and Research, Wageningen, the Netherlands.
Magn Reson Chem. 2019 Sep;57(9):540-547. doi: 10.1002/mrc.4808. Epub 2018 Dec 21.
Lipid oxidation is the main reason for the limited shelf life of mayonnaise. One of the main catalysts of this process is iron, which is introduced in its ferric (Fe(III)) form via phosvitin, an egg yolk phosphoprotein rich in phosphoserines. The binding of Fe(III) to phosvitin and its ability to establish a redox couple with Fe(II) is believed to determine the oxidation rate of unsaturated lipids. In this work, a P NMR based method was developed to quantify loading of phosvitin with Fe(III) and its reductive release. Both features could be quantified in model phosvitin solutions by exploiting the paramagnetic broadening of P NMR signal of phosphoserine residues by Fe(III). This method was then successfully applied to quantify the phosvitin-Fe(III) loading in mayonnaise water phase by liquid NMR, whereas P NMR MAS could only provide a qualitative measure. The P NMR method showed a direct relation between loading of the Fe(III)-phosvitin complex and lipid oxidation.
脂质氧化是蛋黄酱保质期有限的主要原因。这个过程的主要催化剂之一是铁，它以富磷丝氨酸的卵黄磷蛋白（即卵黄磷蛋白）中的三价铁（Fe(III)）形式被引入。Fe(III)与卵黄磷蛋白的结合及其与 Fe(II)建立氧化还原对的能力被认为决定了不饱和脂质的氧化速率。在这项工作中，开发了一种基于 31P NMR 的方法来定量测定 Fe(III)与卵黄磷蛋白的结合及其还原释放。通过利用 Fe(III)对磷酸丝氨酸残基的 31P NMR 信号的顺磁增宽，可以在模型卵黄磷蛋白溶液中定量测定这两个特征。该方法随后成功地应用于通过液体 NMR 定量测定蛋黄酱水相中的卵黄磷蛋白-Fe(III)结合，而 MAS 31P NMR 只能提供定性测量。31P NMR 方法显示出 Fe(III)-卵黄磷蛋白复合物的结合与脂质氧化之间存在直接关系。
