Wenceslao Moreda

Chromatographic analysis of minor constituents in vegetable oils.

The main group of minor constituents belonging to vegetable oils are reviewed. Their importance in the characterization, origin and detection of oil mixtures are considered. Also, the determination of these minor components is of great value in establishing the oil quality and their genuineness. The most commonly used procedures (including the Official methodologies) normally applying chromatographic techniques are reviewed. The interference of each component within the determination of the other minor constituents are discussed. Furthermore, novel procedures for determining those compounds are also presented.

Gas and liquid chromatography of hydrocarbons in edible vegetable oils.

Hydrocarbons, an important part of the minor constituents belonging to vegetable oils are reviewed. Their importance, origin, characterization and detection in edible vegetable oils are considered. The determination of some of them as a means of establishing oil quality and genuineness is also highlighted. The official methodologies, as well as the most commonly procedures used for isolation and analysis are reviewed. Furthermore, novel procedures applying new techniques for determining those compounds are also presented.

Alkyl Esters of Fatty Acids a Useful Tool to Detect Soft Deodorized Olive Oils

Fatty acid alkyl esters (FAAEs) are a family of natural neutral lipids present in olive oils and formed by esterification of free fatty acids (FFAs) with low molecular alcohols. Inappropriate practices during the olive oil extraction process and bad quality of the olive fruits promote their formation. Quantification can be done by isolation with a silica gel solid phase extraction cartridge followed by analysis on a gas chromatograph equipped with a programmed temperature vaporizer injector using a polar capillary column. The application of the method to more than 100 Spanish olive oils from different categories, varieties, and geographical origin allowed for establishing the average content of FAAEs and distinguishing the Spanish protected denomination of origin (PDO) and extra virgin olive oils from other categories of olive oils. Those other categories of oils can be subjected to a mild refining process, which leads to blending with extra virgin olive oils. Studies on low quality oils subjected to mild refining showed that FAAEs remain after that process. Thereby, blends of extra virgin olive and mildly refined low quality olive oils can be detected by their alkyl ester concentrations.

Determination of esters of fatty acids with low molecular weight alcohols in olive oils.

A simple and precise analytical method was developed for the simultaneous determination of squalene and methyl, ethyl, propyl, and butyl esters of fatty acids present in olive and olive pomace oils. A fraction containing squalene and fatty acid alkyl esters was isolated from the oil by solid phase extraction on silica gel cartridges and quantitatively analyzed by gas chromatography. A modification of the procedure allowed the isolation of squalene and esters separately. Repeatability and recovery of the method were good. The method was applied to extra and lampant virgin olive oil categories and also to oils obtained from olive pomace by second centrifugation and solvent extraction. Extra virgin olive oils contained low amounts of fatty acid methyl and ethyl esters, while oils obtained from altered olive or olive pomace showed high concentrations of fatty acid alkyl esters, mainly ethyl esters. Correlation between oil acidity and ethyl esters concentration was poor.

Determination of diacylglycerol isomers in vegetable oils by solid-phase extraction followed by gas chromatography on a polar phase

Diacylglycerol (DG) isomers in vegetable oils were determined by several chromatographic techniques. The use of reversed-phase high-performance liquid chromatography on LC-18 under isocratic conditions was inappropriate, since no complete resolution of the 1,2- and 1,3-isomers appearing at low retention time was achieved. In addition, overlapping of some peaks, absence of peaks of the minor components and interferences by sterols were observed. On the other hand, the isolation of the polar fraction by solid-phase extraction (SPE) using a bonded diol phase and further analysis of the silyl derivatives by capillary GC on 65%-phenyl-methylsilicone, was carried out successfully. No interferences by other components were found and isomerisation by passing the DGs through the SPE column was negligible. The procedure is easy, fast and reproducible, allowing the quantitation and separation of DGs according to their carbon number, their isomeric structure (1,2 and 1,3) and the degree of unsaturation. The effect of unsaturation on the DG retention times depends on the number and arrangement of the double bonds in the molecule. Applications to some vegetable oils are shown.

New method of stationary phase preparation for silver ion column chromatography:: Application to the isolation of steroidal hydrocarbons in vegetable oils

A simple method to prepare silver nitrate loaded silica gel for low pressure silver ion column chromatography is presented. To prepare the packing material, activated silica gel is homogenised with a small volume of aqueous solution of silver nitrate. The effects of water and silver content on the column efficiency, and of elution solvent and light on the recovery, were studied. The procedure was applied to the isolation of steroidal hydrocarbons in olive oils. Separation between 3,5-, 2,4- and 2,5-sterene isomers was achieved.

Triglyceride-Rich Lipoprotein Regulates APOB48 Receptor Gene Expression in Human THP-1 Monocytes and Macrophages

The postprandial metabolism of dietary fats implies that the production of TG-rich lipoproteins (TRL) contributes to the progression of plaque development. TRL and their remnants cause rapid receptor-mediated monocyte/macrophage lipid engorgement via the cell surface apoB48 receptor (apoB48R). However, the mechanistic basis for apoB48 receptor (APOB48R) regulation by postprandial TRL in monocytes and macrophages is not well established. In this study, we investigated the effects of postprandial TRL from healthy volunteers on the expression of APOB48R mRNA and lipid uptake in human THP-1 monocytes and THP-1-derived macrophages. The expression of APOB48R mRNA was upregulated in THP-1 monocytes, but downregulated in THP-1-derived macrophages when treated with postprandial TRL (P < 0.05), in a dose- and time-dependent manner. TG and free cholesterol were dramatically increased in THP-1-derived macrophages (140 and 50%, respectively; P < 0.05) and in THP-1 monocytes (160 and 95%, respectively; P < 0.05). This lipid accumulation was severely decreased (~50%; P < 0.05) in THP-1-derived macrophages by small interfering RNA (siRNA) targeting of APOB48R. Using PPAR and retinoid X receptor (RXR) agonists, antagonists, and siRNA, our data indicate that PPARα, PPARγ, and RXRα are involved in postprandial TRL-induced APOB48R transcriptional regulation. Co-incubation with acyl-CoA synthetase or acyl-CoA:cholesterol acyltransferase inhibitors potentiated the effects of postprandial TRL on the expression of APOB48R mRNA in THP-1 monocytes and THP-1-derived macrophages. Our findings collectively suggest that APOB48R represents a molecular target of postprandial TRL via PPAR-dependent pathways in human THP-1 monocytes and macrophages and advance a potentially important link between postprandial metabolism of dietary fats and atherogenesis.

Sources of contamination by polycyclic aromatic hydrocarbons in Spanish virgin olive oils.

The presence of polycyclic aromatic hydrocarbons (PAHs) in virgin olive oils results from contamination on olive skins and the oil itself during processing. Determination of nine PAHs was carried out by isolation of the hydrocarbon fraction and subsequent clean-up by solid phase extraction, followed by RP-HPLC analysis using a programmable fluorescence detector. Contamination of olive skins depends directly on environmental pollution levels and inversely on fruit size. In the oil mill, PAHs levels were increased by contamination from combustion fumes during the extraction process. Other procedures, such as washing or talc addition during extraction, did not affect PAHs levels. High concentrations of PAHs were only found as a consequence of accidental exposure to contamination, such as direct contact of olives with diesel exhaust and oil extraction in a polluted environment.

Simultaneous determination of long-chain aliphatic aldehydes and waxes in olive oils

A procedure for the simultaneous determination of long-chain aliphatic aldehydes, and aliphatic and triterpenic waxes in virgin olive oils is described. A fraction containing these compounds was isolated from the oil using solid-phase extraction on silica-gel cartridges. The fraction was analyzed by capillary GC on 35%-dimethyl-65%-diphenylpolysiloxane phase using on-column injection. In extra virgin olive oils, the long-chain aliphatic aldehydes with even carbon atom numbers from C22 to C30 were identified by comparison of retention times and mass spectra with those of synthesized standards. The concentration of total aldehydes ranged from 20.2 to 108.0 mg/kg-n-hexacosanal being the most abundant aldehyde. The determination of aliphatic waxes was achieved with similar or better precision than that of the EU official methods.

Rapid Determination of Olive Oil Oxidative Stability and Its Major Quality Parameters Using Vis/NIR Transmittance Spectroscopy

This paper reports the determination of the olive oil stability index (OSI) by multivariate models from the visible and near-infrared spectrum. The technique proposed is rapid and nondestructive and can be used as a multiparametric method. Moreover, it does not require specific instrumentation, and it is environmentally friendly. The determination of the OSI using the Rancimat instrument was used as a reference method. Predictive visible and near-infrared (vis/NIRS) models were obtained from partial least squares (PLS) for the OSI, showing satisfactory performance in independent tests as proven by the R(2) values of 0.93 and 0.94 from the calibration and the residual predictive deviation (RPD) of the external validations of 3.30 and 3.00, respectively. Predictive models for the determination of free fatty acids, peroxide value, and conjugated dienes were also developed, and their satisfactory performances were demonstrated by RPDs of 3.14, 2.84, and 2.56; hence, its multiparametric determination together with OSI would be possible.