Quality evaluation of olive oil by statistical analysis of multicomponent stable isotope dilution assay data of aroma active compounds.

An instrumental method for the evaluation of olive oil quality was developed. Twenty-one relevant aroma active compounds were quantified in 95 olive oil samples of different quality by headspace solid phase microextraction (HS-SPME) and dynamic headspace coupled to GC-MS. On the basis of these stable isotope dilution assay results, statistical evaluation by partial least-squares discriminant analysis (PLS-DA) was performed. Important variables were the odor activity values of ethyl isobutanoate, ethyl 2-methylbutanoate, 3-methylbutanol, butyric acid, E,E-2,4-decadienal, hexanoic acid, guaiacol, 2-phenylethanol, and the sum of the odor activity values of Z-3-hexenal, E-2-hexenal, Z-3-hexenyl acetate, and Z-3-hexenol. Classification performed with these variables predicted 88% of the olive oils' quality correctly. Additionally, the aroma compounds, which are characteristic for some off-flavors, were dissolved in refined plant oil. Sensory evaluation of these models demonstrated that the off-flavors rancid, fusty, and vinegary could be successfully simulated by a limited number of odorants.

Robust intraocular acquisition of the accommodation demand using eyeball movements.

The Artificial Accommodation System is a mechatronic lens implant that will restore the ability of the human eye to accommodate. Therefore, the accommodation demand has to be acquired. One possibility is to measure the vergence angle of the eyeballs in reference to an external field. Using the earth magnetic field as reference the proof of this measuring principle was possible. Still there are drawbacks like high responsivity to interferences and limitations of the measuring range. The new approach is to use the gravity field as reference and thus reduce the responsivity to interferences. The measuring range can be expanded by combining both sensing principles.

Identification of a medicinal off-flavour in mineral water.

The aim of the present study was to identify the compounds responsible for a characteristic medicinal off-odour in mineral water. 2-Dimensional high resolution gas chromatography-mass spectrometry analysis, in combination with olfactometry (HRGC-MS/O), led to the identification of 2-iodophenol and 2-iodo-4-methylphenol as the two compounds exhibiting the medicinal odour notes in mineral water. Determination of odour thresholds of these two compounds in air and water, as well as investigation of their odour characteristics in specific structure-odour activity assays, showed that 2-iodophenol and 2-iodo-4-methylphenol were both extremely potent odour substances with odour thresholds down to 0.03 and 0.0003ng/L air and 0.313 and 0.009mug/L water, respectively. The higher odour potency of 2-iodo-4-methylphenol suggests that this compound is primarily responsible for the medicinal off-odour. Furthermore, the same proportion of the panellists who were not able to detect the off-odour in mineral water exhibited drastically decreased sensibility to 2-iodo-4-methylphenol, but not to 2-iodophenol, which supports this hypothesis.

Binding studies and computer-aided modelling of macromolecule/odorant interactions.

Odorant-to-biopolymer (proteins and polysaccharides) binding properties influence the partition coefficients of odorant/matrix mixtures and depend on the molecular structure of the guest and the host. While air/solvent partition coefficients of odorants influence the flavor intensity of compounds in the headspace above the solvent, more complex mechanisms are proposed for the binding of a molecule to a food matrix. Odorant air/solvent partition coefficients are dependent on both the physico-chemical properties of odorant and solvent. Binding affinities for flavor compounds on various biopolymers can be estimated by calculation of physico-chemical descriptors for the odorants. Binding affinities of gamma- and delta-lactones (C7-C11) to bovine serum albumin (BSA) and beta-lactoglobulin (BLG) were investigated by ultracentrifugation and equilibrium-dialysis techniques. Quantitative structure-activity relationships (QSAR) of lactone binding on proteins (BLG and BSA) were performed by the measurement of lipophilicity and H-bond strength. Large differences in observed protein-binding properties for the various compounds clearly demonstrated that structure-activity relationship was significantly influenced by the lipophilicity of the odorant. If the structure of the receptor molecule is known, computational ligand-macromolecule docking experiments can be used to predict binding affinities for unknown compounds with the receptor molecule. A BLG-lactone binding position, not previously reported in the literature, has been identified and confirmed by competitive binding studies. A model has been developed to estimate the free energy of binding of odorants to biopolymers. Estimated free energies of binding of lactones with BLG from computational methods were in very good agreement with the experimentally obtained results.