Analysis of the wax ester fraction of olive oil and sunflower oil by gas chromatography and gas chromatography‐mass spectrometry

Abstract

The wax ester fractions of solvent-extracted sunflower oil and "extra virgin" olive oil were obtained by solidphase extraction and subsequently subjected to gas-chromatographic and gas chromatographic-mass spectrometric analysis. The comprehensive qualitative analysis of these fractions, which was carried out by the interpretation of mass spectral data, revealed several types of wax esters. In olive oil, shortchain, even-numbered wax esters, saturated and unsaturated long-chain, even-numbered wax esters, benzyl esters, and the diterpenic esters phytyl and geranylgeranyl ester (the latter as a minor component) are present. With the exception of benzyl esters, all these esters occur in sunflower oil as well, but in considerably different amounts compared to those in olive oil. Whereas unsaturated wax esters are present in a negligible amount, diterpenic esters, mainly geranylgeranyl esters, represent the major part of the wax ester fraction.Paper no. J9809 in JAOCS 78, 881-888 (September 2001) Wax esters (WE) are part of the unsaponifiable matter in vegetable oils and are of interest to the oil-processing industry for various reasons. The WE content is used as a quality parameter for high-quality oils such as cold-pressed "extra virgin" olive oils (1). For instance, the European Union Regulation No. 183/93 requires the quantitation of WE in olive oils, because solvent-extracted olive oils contain a considerably higher amount of waxes than oils obtained by cold pressing (2). In addition, typical WE patterns or specific WE enable the recognition of adulteration of high-quality oils with cheaper oils, for example, the addition of sunflower oil to olive oil (3). The isolation of WE in vegetable oils has been performed by on-line high-performance liquid chromatography-gas chromatography (HPLC-GC) (3-6), by column chromatography (7), by HPLC (8,9), and, recently, by solid-phase extraction (SPE) (10,11) with subsequent capillary GC analysis. None of these techniques requires saponification of the WE fraction. Therefore, WE can be determined without any alteration of their structure. These analytical methods allow isolation and quantitation of WE according to their number of carbon atoms and their degree of unsaturation, but a complete qualitative analysis as well as elucidation of isomeric constitution can only be carried out by mass spectrometric (MS) methods.WE in olive and sunflower oils are of particular interest, as already mentioned, but there is a lack of data concerning their detailed structures and their isomeric composition. In the case of olive oil, a GC-MS analysis of WE in extracted olive oil published by Bianchi et al. (12) revealed the presence of esters with alcohols (AL) in the range of AL 1-AL 6, esters of oleic acid with long-chain aliphatic alcohols AL 22-AL 38, and benzyl alcohol esters of the long-chain saturated fatty acids (FA) FA 26 and FA 28.The composition of sunflower WE has been determined only by the analysis of hydrolysis products. WE were hydrolyzed, and fatty acids and alcohols were an...

Fatty Acid Phytyl Ester Synthesis in Chloroplasts of Arabidopsis

“…It is believed that bacteria accumulate fatty acid phytyl esters for carbon and energy storage. Phytyl esters were found in green algae and hornworts (Buchanan et al, 1996;Rager and Metzger, 2000), in some Amazonian plant species (Pereira et al, 2002), and in the seed oils of sunflower and olive oil (Reiter and Lorbeer, 2001). Etiolated barley (Hordeum vulgare) seedlings accumulate phytyl esters after exposure to light, suggesting that this lipid class takes up excess phytol produced during deetiolation (Liljenberg, 1977).…”

Overexpression of an Isoprenyl Diphosphate Synthase in Spruce Leads to Unexpected Terpene Diversion Products That Function in Plant Defense

“…Esters of geranylgeraniol with fatty acids were already described in P. abies wood (Ekman, 1980), in mosses (Liljenberg and Karunen, 1978;Karunen et al, 1980), and in other plants (Lütke-Brinkhaus et al, 1985;McKibben et al, 1985;Jondiko and Pattenden, 1989;Reiter and Lorbeer, 2001;Biedermann et al, 2008). Esters with geraniol instead of geranylgeraniol are also known in rose (Rosa spp.)…”

Phytol and Phytyl Fatty Acid Esters: Occurrence, Concentrations, and Relevance

“…PFAE were also detected in plant parts commonly consumed by humans (Table ). They were found to be present in the wax ester fraction of several edible oils, namely hazelnut, palm, safflower, linseed, sesame, grape seed, and soybean oil as well as olive and sunflower oil . Given the low contribution of wax esters to total lipids, the concentrations in the oils were rather negligible and quantities were not reported except for one study on olive oil (see this section, below).…”