Institute of Food Chemistry, University of Hohenheim, Stuttgart, Germany.
J Agric Food Chem. 2012 Jun 20;60(24):6103-7. doi: 10.1021/jf301373k. Epub 2012 Jun 7.
The differentiation of nonrefined (e.g., cold-pressed) and refined edible oils is an important task in food control because of the higher commercial value of the former. Here, we explored the suitability of the relative abundance of cis-phytol as a marker for authentication of nonrefined edible oils. Phytol, the tetramethyl-branched, monoenoic alcohol, is found widespread in nature as a part of chlorophyll. In chlorophyll, only trans-phytol is found. In this study, we present a method for the analysis of the phytol isomers, considering that traces of cis-phytol (contributing 0.1% to the phytol content) can be determined next to trans-phytol. For this purpose, phytol was gathered with the unsaponifiable matter from the oil, trimethylsilylated, and analyzed by gas chromatography coupled to mass spectrometry. With this method, 27 samples of edible oils (16 refined and 11 nonrefined edible oils) were analyzed for the abundance of cis-phytol relative to trans-phytol. In the nonrefined oils (e.g., olive oil, rapeseed oil, maize oil, and sunflower oil), cis-phytol contributed 0.1% (n = 3) or less (n = 8) to the phytol content. In contrast, the refined olive oils (n = 4) contained a share of 1.3-3% cis-phytol; the refined rapeseed oil (n = 3) contained a share of 0.7-1.0% cis-phytol; and the refined sunflower oil (n = 4) contained a share of 0.3-0.9% cis-phytol. Only one refined pomegranate kernel did not contain cis-phytol. The phytol concentration was not suited to distinguish nonrefined from refined oils. In contrast, our data suggest that the virtual absence of cis-phytol can be used as a marker for nonrefined (e.g., cold-pressed) edible oils.
非精炼（例如冷榨）和精炼食用油的区分是食品控制中的一项重要任务，因为前者具有更高的商业价值。在这里，我们探讨了顺式植醇的相对丰度作为非精炼食用油鉴别的标志物的适用性。植醇是一种广泛存在于自然界中的四甲基支链单烯醇，是叶绿素的一部分。在叶绿素中，只发现反式植醇。在这项研究中，我们提出了一种分析植醇异构体的方法，考虑到顺式植醇（占植醇含量的 0.1%）可以与反式植醇相邻存在。为此，将油中的不皂化物与植醇一起收集，进行三甲基硅烷基化，并通过气相色谱-质谱联用进行分析。使用这种方法，对 27 种食用油（16 种精炼食用油和 11 种非精炼食用油）的顺式植醇相对于反式植醇的丰度进行了分析。在非精炼油（例如橄榄油、菜籽油、玉米油和葵花籽油）中，顺式植醇对植醇含量的贡献为 0.1%（n = 3）或更少（n = 8）。相比之下，精炼橄榄油（n = 4）含有 1.3-3%的顺式植醇；精炼菜籽油（n = 3）含有 0.7-1.0%的顺式植醇；精炼葵花籽油（n = 4）含有 0.3-0.9%的顺式植醇。只有一种精炼的石榴籽油不含顺式植醇。植醇浓度不适合区分非精炼油和精炼油。相比之下，我们的数据表明，顺式植醇的几乎不存在可以用作非精炼（例如冷榨）食用油的标志物。
