Comparaison des performances des modèles d'analyse discriminante PLS et SVM

Les performances des modèles d’analyses discriminantes PLS (Partial Least Squares) et SVM (Support Vector Machines) ont été comparées dans une étude qui avait pour objectif de discriminer des spectres proches infrarouges sur base d'images hyperspectrales de racines et de pailles de froment en vue de les quantifier

Use of near infrared hyperspectral imaging and chemometrics to study root systems.

peer reviewedLors d’études de systèmes racinaires sur base de prélèvements de carottes de sol, une étape préliminaire à la quantification racinaire consiste à éliminer manuellement les résidus de cultures et les particules de sol récupérés avec les racines lors du lavage des échantillons. En présence de racines de différentes espèces, cette étape s'accompagne d'un tri des racines selon différents critères. Pour faciliter et réduire le temps nécessaire à cette étape fastidieuse, la discrimination de ces éléments a été réalisée sur base d’images hyperspectrales prises en proche infrarouge. Les échantillons lavés et séchés ont été passés sous une caméra qui enregistre, pour chaque pixel de l’image, un spectre en proche infrarouge. Ces spectres sont liés à la nature physico-chimique des éléments présents sur l’image et ont été analysés à l’aide d’algorithmes d’analyses discriminantes qui permettent de les classer et de donner la nature de chaque pixel de l’image. Sur base du nombre de pixels classés comme étant des racines et grâce à la relation linéaire reliant ce nombre de pixels à la masse de racines présente dans l'échantillon, il fut finalement possible quantifier des racines au sein d’échantillons de sol sans devoir réaliser un tri manuel préalable et les peser. Cette méthode a été testée avec succès en froment et a permis de mettre très clairement en évidence l’effet du travail du sol sur le développement du système racinaire. Elle est également été testée sur une culture associée de froment et de pois afin de quantifier séparément les racines des 2 espèces.In studies on root systems using the soil coring method, roots, crop residues and soil particles extracted after washing of soil samples need to be manually sorted before root quantification. If different species are present in the sample, their discrimination is based on several criteria. In order to reduce the complexity and the time needed for this tedious sorting step, near infrared hyperspectral imaging was used to discriminate all these elements. Images of washed and dried samples were acquired with a camera saving, for each pixel, a near infrared spectrum. These spectra are linked to the physicochemical nature of the elements visible on the hyperspectral images and were analyzed with discriminant algorithms allowing their discrimination and to link each pixel spectrum to the nature of the elements. According to the number of pixels classified as roots and thanks to the linear relationship between the number of pixels and the root biomass in the sample, it was possible to quantify roots in soil samples without manual sorting and weighing. This methodology was successfully tested on winter wheat roots and highlighted the tillage effect on root system development. It was also tested on wheat-pea intercropping in order to quantify separately the roots of each species

Espectroscopía: Desarrollo en instrumentación y análisis

This review presents the characteristics, advantages, limits and potential of three spectroscopic techniques: near-infrared spectroscopy (NIR), mid-infrared spectroscopy (MIR) and Raman spectroscopy. The theoretical aspects related with these techniques, the information that can supplied and the main features of the instrumentation are presented and briefly discussed. The last part of the review concerns the application of the spectroscopy to food analysis, with special emphasis on the lipid analysis. The illustrations and examples have been chosen to demonstrate the importance of spectroscopic techniques both in process (on-line) control and in laboratories for the analysis of major or minor compounds.Este artículo de revisión presenta las características, ventajas, límites y potencial de tres técnicas espectroscópicas: las espectroscopias del infrarrojo cercano, del medio infrarrojo y Raman. Se presentan, y discuten brevemente, los aspectos teóricos relacionados con estas técnicas, la información que pueden suministrar, y las principales características de la instrumentación. La última parte de la revisión esta dedicada a las aplicaciones de la espectroscopia en análisis de alimentos, con especial énfasis en análisis de lípidos. La ilustraciones y los ejemplos se han elegido para demostrar la importancia de las técnicas espectroscópicas en los procesos en-línea y en los laboratorios en el análisis de componentes mayoritarios y minoritarios

Determining milk isolated and conjugated trans-unsaturated fatty acids using Fourier transform Raman spectroscopy

The feasibility of Raman spectroscopy in combination with partial least-squares (PLS) regression for the determination of individual or grouped trans-monounsaturated fatty acids (trans-MUFA) and conjugated linoleic acids (CLA) in milk fat is demonstrated using spectra obtained at two temperature conditions: room, temperature and after freezing at -80 degrees C. The PLS results displayed capability for direct semiroutine quantification of several individual CLA (cis-9,trans-11 and trans-10,cis-12 C18:2) and trans-MUFA (trans-4-15 C18:1) in minor concentrations (below 1.0 g/100 g of milk fat). Calibration models were based on reference data cross-correlation or determined by specific scattering signals in the Raman spectra. Distinct bands for trans-MUFA (1674 cm(-1)) and CLA (1653 cm(-1)) from the trans isolated and cis,trans conjugated C=C bonds were identified, as well as original evidence for the temperature effect (new bands, peak shifts, and higher intensities) on the Raman spectra of fatty acid methyl ester and triacylglyceride standards, are supplied

Bovine blood biomarkers as a way of processed animal proteins detection in feedingstuffs

peer reviewedThe prohibition of using animal by-products in feedingstuffs depends on two factors: their nature defined by the tissue/cell type and the species of origin, and on their destination (pets, fur animals or other farmed animals). Proteomics is particularly well-suited to the purpose of PAPs detection as it is a tissue and species-specific method. The aim of this study was the identification and the selection of specific peptide biomarkers using tandem mass spectrometry for the detection of bovine blood products and blood meals in animal feed. Twenty-nine samples of blood meals and blood products (plasma or haemoglobin powder) of porcine, poultry and bovine origin as well as three milk products and two fish meals were analysed using a Q TOF mass spectrometer. Vegetal feed samples adulterated with 1% or 10% of bovine plasma powder, haemoglobin powder or blood meal were also analysed to evaluate the applicability of the method. Four proteins of interest were highlighted: Alpha-2-macroglobulin, apolipoprotein A-1, serotransferrin and haemoglobin (α and β chains). From these proteins, sixteen peptides were identified as potential bovine blood biomarkers in feedingstuffs. Nine of them could be used for the detection of plasma powder and seven of them for haemoglobin powder or blood meal. The evaluation of these peptides by a search against NCBInr database revealed that some of them could also be used to detect other ruminant bloods such as ovine or caprine ones. These preliminary results are promising. Efforts are now focused to improve the protocol in order to increase the sensitivity of the method as regards the selected proteins

Research on crude protein and digestibility of Arnica montana L. using conventional NIR spectrometry and hyperspectral imaging NIR

peer reviewedaudience: researcher, professional, student, popularizationArnica montana L. (AM) is considered a medicinal plant, used as hay in feed ration. The aim of this study is to assess the prediction of protein content and in vitro organic matter digestibility value in grass mixtures containing Arnica montana L., and in a second step to check if these values have a positive or negative influence in the mixtures. Crude protein has been selected because it is one of the most important quality parameters of forages as nutritional element used in animal feeding. The protein is required on a daily basis for maintenance, lactation, growth and reproduction, but is important for agriculture too, because a high content of protein makes it an important source of feed. The digestibility is also important, because it refers to the extent to which a feedstuff is absorbed in the animal body as it passes through an animal’s digestive tract. In this study, the Weende system (the Kjeldahl method) for the protein content, together with the enzymatic technique for digestibility, was applied and used in combination with non-destructive methods, like those based on the Near Infrared Spectroscopy (NIRS) or the Near Infrared Hyperspectral Imaging. Based on NIR imaging system data, the PLS-DA was used to discriminate between the classes with AM and classes without AM, as well as to build a model that could be used to predict the composition of mixtures. More than 99% correct prediction for AM was obtained. The crude protein content of the hay determined by classical method decrease from the type of meadow Agrostis capillaris L. - Festuca rubra L. (15.22%) until to the pure sample of Arnica montana L. (11.19%); however, the digestibility was highest in the pure sample of Arnica montana L. (84.13%) and lowest in samples from the type of meadow Agrostis capillaris L. - Festuca rubra L. (57.18%) or in samples with the participation of Arnica montana L. This study should lead to a more important point, which is to verify whether the medicinal properties of Arnica montana L. can be transferred or not to milk production through the dairy cow feed.POSDRU/6/1.5/S/20 (PhD Program