Biomedical subjects

P Pollien

Publications and source records attributed to P Pollien.

3 recordsLinked to original sources

PubMed2000

Solid-phase microextraction method development for headspace analysis of volatile flavor compounds.

Solid-phase microextraction (SPME) fibers were evaluated for their ability to adsorb volatile flavor compounds under various conditions with coffee and aqueous flavored solutions. Experiments comparing different fibers showed that poly(dimethylsiloxane)/divinylbenzene had the highest overall sensitivity. Carboxen/poly(dimethylsiloxane) was the most sensitive to small molecules and acids. As the concentrations of compounds increased, the quantitative linear range was exceeded as shown by competition effects with 2-isobutyl-3-methoxypyrazine at concentrations above 1 ppm. A method based on a short-time sampling of the headspace (1 min) was shown to better represent the equilibrium headspace concentration. Analysis of coffee brew with a 1-min headspace adsorption time was verified to be within the linear range for most compounds and thus appropriate for relative headspace quantification. Absolute quantification of volatiles, using isotope dilution assays (IDA), is not subject to biases caused by excess compound concentrations or complex matrices. The degradation of coffee aroma volatiles during storage was followed by relative headspace measurements and absolute quantifications. Both methods gave similar values for 3-methylbutanal, 4-ethylguaiacol, and 2,3-pentanedione. Acetic acid, however, gave higher values during storage upon relative headspace measurements due to concurrent pH decreases that were not seen with IDA.

Chromatography, Gas↗

PubMed1999

Use of solid-phase microextraction for measuring oil-water partition coefficients and correlation with high-performance liquid chromatographic methods for lipophilicity.

For flavour compounds, lipophilicity is often estimated by the partition coefficient between oil and water (log Koil-water), which is highly relevant to food. A modification of the shake-flask method is reported here where compounds are quantified in the two phases using solid-phase microextraction (SPME). SPME's highly sensitivity to non-polar compounds facilitates quantification in the water phase. Twelve flavour compounds representing a broad range of lipophilicities and functional groups were analysed by two methods. Their log Koil-water was determined using SPME quantitation and their log k(w) using a reversed-phase HPLC methodology. The isocratic capacity factor at 60% methanol and predicted log P value also showed high correlation factors with other methods. The octadecyl silylated surface of the HPLC column provides a matrix that interacts with lipophilic compounds where the retention time is the indication of lipophilicity. Both methods gave reproducible results (median 3% and 4% RSD) and similar but not identical values for lipophilicity. The relationship between the two methods is log k(w) =0.85 log Koil-water +0.48 with a correlation coefficient of 0.94. The new SPME detection method, with the ability to quantify limonene and 2-pentylfuran at 1 ppm in the water phase, is preferred for flavour compound analysis due to the applicability of oil-water partitioning in food.

Buffers↗

PubMed1999

First attempt of odorant quantitation using gas chromatography-olfactometry.

An aroma compound was quantitated for the first time by GC-olfactometry (GC-O) on the basis of the detection frequency of odorants by a panel of 8-12 persons. The method was previously optimized regarding the coincidence of olfactometric peak apexes and the repeatability of peak height and area over 4 months. The number of required calibration points and the confidence interval of the curve were investigated. This technique was then tested by quantifying a model solution of 1-octen-3-one. The standard addition method was found to be unsuitable in this context, but external calibration gave excellent results in the ppt range. GC-O was then challenged using one of the most sensitive and selective methods, GC/MS, to quantitate 1-octen-3-one in coffee, a complex aroma. Results showed performances comparable to GC/MS/MS for this odorant, or even better as the latter required 75-500 times more sample to perform the quantitation. However, at such a low concentration, overestimation cannot be excluded with either technique because of possible coelution of odorants or isobaric ions, respectively. These results show that GC-olfactometry can compete with the most sensitive and selective techniques, such as MS, for determination of extremely intense odorants, because little sample preparation is required and there is no need for the synthesis of labeled compounds.

Calibration↗