Search results for " Analytical"
showing 10 items of 1453 documents
The Hierarchical Agglomerative Clustering with Gower index: a methodology for automatic design of OLAP cube in ecological data processing context
2015
In Press, Corrected Proof; International audience; The OLAP systems can be an improvement for ecological studies. In fact, ecology studies, follows and analyzes phenomenon across space and time and according to several parameters. OLAP systems can provide to ecologists browsing in a large dataset. One focus of the current research on OLAP system is the automatic design of OLAP cubes and of data warehouse schemas. This kind of works makes accessible OLAP technology to non information technology experts. But to be efficient, the automatic OLAP building must take into account various cases. Moreover the OLAP technology is based on the concept of hierarchy. Thereby the hierarchical clustering m…
Reconstruction of hyperspectral cutaneous data from an artificial neural network-based multispectral imaging system.
2011
International audience; The development of an integrated MultiSpectral Imaging (MSI) system yielding hyperspectral cubes by means of artificial neural networks is described. The MSI system is based on a CCD camera, a rotating wheel bearing a set of seven interference filters, a light source and a computer. The resulting device has been elaborated for in vivo imaging of skin lesions. It provides multispectral images and is coupled with a software reconstructing hyperspectral cubes from multispectral images. Reconstruction is performed by a neural network-based algorithm using heteroassociative memories. The resulting hyperspectral cube provides skin optical reflectance spectral data combined…
Analytical comparison and sensory representativity of SAFE, SPME, and Purge and Trap extracts of volatile compounds from pea flour
2012
Pisum sativum is of great economic and nutritional interest due to its protein content. Nevertheless, pea products are underused as a protein source in human food because of their strong beany flavour. Therefore, the objective of this study was to select an efficient and representative method to extract volatile molecules of pea flour. In the first step, three extraction methods were chosen: solid phase micro extraction (SPME); Purge and Trap extraction and solvent assisted flavour evaporation (SAFE). The corresponding extracts were analysed by gas chromatography coupled with mass spectrometry. In the second step, the sensory representativity of the extracts was assessed either by direct ga…
Computerized delimitation of odorant areas in gas-chromatography-olfactometry by kernel density estimation: Data processing on French white wines
2017
International audience; GC-O using the detection frequency method gives a list of odor events (OEs) where each OE is described by a linear retention index (LRI) and by the aromatic descriptor given by a human assessor. The aim of the experimenter is to gather OEs in a total olfactogram on which he tries to delimit odorant areas (OAs), then to compute each detection frequency. This paper proposes a computerized mathematical method based on kernel density estimation that makes up the total olfactogram as continuous and differentiable function from the OEs LRI only. The corresponding curve looks like a chromatogram, the peaks of which are potential OAs. The limits of an OA are the LRI of the t…
A HS-SPME-GC-MS analysis of IR heated wood: Impact of the water content on the depth profile of oak wood aromas extractability
2013
http://www.sciencedirect.com/science/article/pii/S0963996913003736; International audience; Controlled and reproducible IR heat treatments were applied to oak wood surfaces in order to establish a depth-profiled picture of the extractability of volatile compounds, with particular emphasis on the impact of the initial water content. Headspace-solid phase microextraction-gas chromatography coupled to mass spectrometry (HS-SPME-GC-MS) has been used to compare the concentrations of six aroma compounds (vanillin, furfural, eugenol; guaiacol and cis- and trans-whisky lactones) in hydroalcoholic extracts of series of slices representative of the first 8 mm of the wood facing the IR source. Results…
An original approach for gas chromatography-olfactometry detection frequency analysis: Application to gin
2012
Abstract Gas Chromatography-Olfactometry (GC-O) is a technique that lies halfway between physicochemical and sensory analysis and involves the perception of volatile flavour compounds, separated by gas chromatography, by the human nose. Of the different GC-O procedures available, detection frequency has been proved to be more rapid and more repeatable, even with an untrained panel. This characteristic regarding the panel is often not considered when dealing with the sensory attributes determined by assessors. An original approach to GC-O using the detection frequency procedure has been developed and tested on two types of gin and made it possible to benefit from sensory data. The panel cons…
Impact of lipid extraction on the dearomatisation of an Eisenia foetida protein powder
2010
www.elsevier.com/locate/foodchem ; FSTA:2010-Sp0197; International audience; Delipidation was studied as a way to dearomatise a non-conventional protein powder obtained from Eisenia foetida earthworms. In the first step, we studied the impact of several factors such as solvent type, extraction method and particle size on the yield of extracted lipids. Lipid extraction from samples was considerably improved using an ultrasound method with a chloroform/methanol mixture and small particle size. In the second step, the volatile compounds were extracted from the delipidated protein powder by the SAFE extraction method and by the HS-SPME method, and were further analysed by GC-MS. The chloroform/…
Dry vs soaked wood: Modulating the volatile extractible fraction of oak wood by heat treatments
2012
The aim of this study was to analyze the impact of the water content of wood on the concentrations of volatile compounds which can be extracted after heat treatments. Head Space-Solid Phase Micro Extraction Gas Chromatography coupled to Mass Spectrometry (HS-SPME GC-MS) has been used to compare the concentrations of six aroma compounds (vanillin, furfural, eugenol, guaiacol and cis- and trans-whisky lactones) in hydroalcoholic extracts of heated oak wood samples either previously soaked in hot water or not. Except for eugenol, concentrations of extracted aromas appeared to be lower in soaked woods than in dry woods for temperatures up to 200 °C. If a delaying effect of water could explain s…
Prefractionation of aroma extracts from fat-containing food by high-performance size-exclusion chromatography
1996
A method for the prefractionation of aroma extracts of fat-containing food using high-performance size-exclusion chromatography is presented. The aim was to obtain a fraction of volatile compounds with a residual triglyceride content as low as possible, in order to allow its direct analysis by gas chromatography. Two different mobile phases, diethyl ether and dichloromethane, were tested and the elution volumes of triglycerides and a large variety of aroma compounds were measured. The quality of separation between triglycerides and volatile compounds as a function of column load was studied. The method was successfully applied to the analysis of goat cheese volatiles.
Retention behaviour of volatile compounds in normal-phase high-performance liquid chromatography on a diol column
1993
Abstract Retention data on a diol column for over 300 compounds of the chemical classes usually contained in aroma extracts of plants and foodstuffs are reported. A concept that largely corrects for minor fluctuations of the mobile phase composition and of the flow-rate was used to measure capacity factors. The mobile phase was composed of pentane and diethyl ether. The high volatility of these two solvents makes the method perfectly adaptable to the prefractionation of aroma extracts and the semi-preparative isolation of compounds. Non-polar compounds such as hydrocarbons are not retained on diol. Polar compounds can be readily eluted, with the exception of strong acids and bases.