G. Lercker

Pressurized liquid extraction of lipids for the determination of oxysterols in egg-containing food.

Pressurized liquid extraction (PLE, ASE) was compared with the Folch procedure (a solid-liquid extraction with chloroform/methanol 2:1, v/v) for the lipid extraction of egg-containing food; the accuracy of PLE for the quantitative determination of oxysterols in whole egg powder was evaluated. Samples of spray-dried whole egg, an Italian vanilla cake (Pandoro) and egg noodles were used. Two different extraction solvents (chloroform/methanol 2:1, v/v, and hexane/isopropanol 3:2, v/v) were tested at different extraction temperatures and pressures (60 degrees C at 15 MPa, 100 degrees C at 15 MPa, 120 degrees C at 20 MPa). No significant differences in the lipid recovery of the egg powder sample using PLE were found. However, PLE of the vanilla cake and egg noodles with the chloroform/methanol mixture was not selective enough and led to the extraction of a non-lipid fraction, including nitrogen-containing compounds. In the same samples, the pressurized hexane/isopropanol mixture gave a better recovery result, comparable to that obtained using the Folch method. Cholesterol oxidation products of the Folch extract and the pressurized liquid extract of spray dried egg powder (obtained with hexane/isopropanol 3:2, v/v, at 60 degrees C and 15 MPa) were determined by gas chromatography. PLE performed under these conditions is suitable to replace the Folch extraction, because the differences between the two methods tested were not statistically significant. Moreover, PLE shows important advantages, since the analysis time was shortened by a factor of 10, the solvent costs were reduced by 80% and the use of chlorinated solvents was avoided.

Solid-phase extraction–thin-layer chromatography–gas chromatography method for the detection of hazelnut oil in olive oils by determination of esterified sterols

The sterol composition of extra virgin olive oil is very characteristic and, thus, has become a helpful tool to detect adulterations with other vegetable oils. Special attention has been addressed to the separate determination of the free and esterified sterol fractions, since both have different compositions and can thus provide more precise information about the actual origin of the olive oil. In the case of admixtures with small amounts of hazelnut oil, this approach can be extremely useful, because the similarity between the fatty acid compositions of both oils hampers the detection of the fraud. A hyphenated chromatographic method was developed for a sensitive and precise determination of esterified sterols in olive oils. The oil was subjected to silica solid-phase extraction (SPE) fractionation, cold saponification of the collected fraction and purification on silica TLC. The sterol band was then injected into an SPB-5 (30 m x 0.25 mm I.D., 0.25 microM film thickness) and the ratio [% campesterol x (% 7-stigmastenol)2]/(% 7-avenasterol) was calculated. The method was tested on extra virgin olive oil; good sterol recoveries and repeatability were obtained. The results were compared with another method. which has a different sample preparation sequence (silica column chromatography, hot saponification and silica TLC). Similar results were achieved with both methods; however, the SPE-cold saponification-TLC-capillary GC was faster, required less solvent and prevented sterol decomposition. The SPE-method was applied to an admixture with 10% of hazelnut oil and to a screening of 11 oils (husk oil, virgin and refined olive oils) from different Mediterranean countries.

Components of royal jelly: I. Identification of the organic acids

This present work characterizes the fatty acid constituents of the lipid fraction of royal jelly. Among the organic acids found after fractionation by thin layer chromatography of the corresponding methyl esters, the following compounds were identified by combined GC-MS: saturated and unsaturated linear fatty acids, saturated and unsaturated linear and branched dicarboxylic acids, mono-and dihydroxy acids. The most common characteristic of the organic acids was that most contained 8 or 10 carbon atoms, whether saturated or unsaturated, linear or branched.

Improvement of extraction procedure for biogenic amines in foods and their high-performance liquid chromatographic determination

A high-performance liquid chromatography method is described for the simultaneous determination of the biogenic amines tryptamine, 2-phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine, and spermine in cheese. The optimization of the procedure for the extraction of amines from the matrix is described. The separation of dansyl derivatives of the amines was achieved by reversed-phase liquid chromatography with gradient elution, followed by UV detection at 254 nm. The mobile phase was acetonitrile-0.01 M phosphate buffer (pH 7)-water. Under these conditions, rapid elution of the amines in less than 13 min was obtained. Validation of the method included calibration experiments, addition of standard amines for the determination of amine recoveries and repeatability tests.

Analysis of green tea catechins: comparative study between HPLC and HPCE

Abstract A comparison between a borate–phosphate–SDS based MEKC and an RP-HPLC method for the separation of seven tea catechins and gallic acid in a green tea extract is here proposed. Under optimised conditions, HPCE offered several advantages respect to time of analysis (compounds were separated within 4.5 min), sensitivity (HPCE LODs were about 20–100 times lower than HPLC ones) and solvent consumption. HPCE displayed excellent migration time repeatability (RSD% on MT

Veiled extra-virgin olive oils : dispersion response related to oil quality

A cloudy (“veiled”) extra-virgin olive oil was stored 10 mon at room temperature and monitored at 15-d intervals. The oil was very stable under oxidizing conditions; a slight increase in free acidity (from 0.2 to 0.3%, expressed as oleic acid), a notable rise in the amount of diacylglycerols and a minor increase in peroxide content were observed. Turbidity disappeared after a few months due to chemical bonding between a nitrogen-containing component and the free acids that were released over time. The material in suspension, therefore, contained some chemical groups capable of acting as antioxidants.

Separation and analysis of phospholipids in different foods with a light-scattering detector

A method for the separation of phospholipids (PL) from total lipids by solid-phase extraction (SPE) with reversephase C8 cartridges is described. The method was validated with a standard mixture of PL and applied to natural food matrixes, such as egg, chicken meat, salami, and ripened cheese. The recovery of PL ranged between 93 and 99.7% and was evaluated by an organic phosphorus spectrophotometric determination. The egg powder PL fraction obtained by SPE contained about 20% (w/w) nonpolar PL material when 100–150 mg of lipids were loaded onto the cartridge. Higher percentages of nonphospholipid components (30–43%) were obtained when the amount of lipids loaded was below or above the 100–150 mg range. The purified PL fractions were analyzed by high-performance liquid chromatography (HPLC) with an evaporative light-scattering detector. Good HPLC performance was observed even with low-purity SPE fractions (43% nonphospholipid material).

Direct gas chromatographic analysis of the unsaponifiable fraction of different oils with a polar capillary column

The analysis of the unsaponifiable fraction of several oil samples was performed by a new gas chromatographic technique with a polar column of high thermal stability. This column was adequate for fractionating sterols, methyl sterols and alcohols of the unsaponifiable matter, and allowed the detection of peaks usually unresolved with nonpolar columns.

High resolution gas chromatographic determination of diterpenic alcohols and sterols in coffee lipids

SummaryThe composition of the unsaponifiable fraction of coffee lipids extracted before and after roasting was determined in two coffee types (Arabica and Robusta) of different geographic origin. Component identification was performed by gas chromatography-mass spectrometry. Large amounts of diterpene mono- and di-alcohols were found in both varieties; cafestol, kahweol and 16-O-methylcafestol were identified. Other components that were partly generated during roasting were also identified; these compounds seem to arise from the dehydration of cafestol and dehydrocafestol.

A study on cashew nut oil composition

Eight samples of cashew nut oil were assayed, and the component triacylglycerols, fatty acids and several unsaponifiable compounds were analyzed by gas chromatography (GC) and high-performance liquid chromatography (HPLC). Total lipid amount, unsaponifiable percentage, fatty acids, sterols, triterpene alcohols and tocopherols are reported here. The combination of GC and HPLC enhanced the resolution of compound classes.