Hydrocarbon influence on denitrification in bioturbated Mediterranean coastal sediments

An in situ experiment has been carried out inbioturbated Mediterranean coastal marine sediments (Gulfof Fos) in order to study the influence of hydrocarbons ondenitrification after 1, 4 and 6 months. In theabsence of hydrocarbons in the control sediments, the presenceof macrofauna stimulated denitrificationby 160%. This stimulation is induced by sediment reworkingthat favours both direct NO-3 supply fromthe water column and the penetration of O{2}, which in turnstimulated nitrification, the other source ofNO-3 in sediment. The presence of hydrocarbons in theexperimental sediments either stimulated orinhibited the denitrification. The denitrification response tothe presence of hydrocarbon is dependent onthe quantity of matter buried by the macrofauna activity. Insmall quantities, the organic matter relatedto hydrocarbons 120% enhanced the denitrification compared tothe controls. On the other hand, whenburied hydrocarbon concentrations were higher (>100 mgsaturated hydrocarbon fraction kg-1 drysediment), the denitrification was inhibited.On the basis of the results obtained, a descriptive model ofthe patterns of denitrification in relation to the presence ofmacrofauna and the distribution of hydrocarbons in sediments is proposed

La composition chimique de l'huile de noix (Juglans regia L.) dépend de la variété, de la localité, du processus d'extraction et des conditions de stockage : Une étude complète

International audienceThis review presents a comprehensive synthesis of walnut oil chemical composition data (major and minor compounds) collected from the literature according to the varieties and the geographic origins of walnuts, and to the oil extraction processes. Considered as influencing factors, pre-and post-harvest treatment parameters of in shell-walnut and kernels were identified and works on oil stability were discussed according to walnut pretreatment, oil extraction processes and their storage conditions. Most studies dealt with the quantification of fatty acids and tocopherols. There has been less interest in the triacylglycerol composition and minor components (sterols, volatiles, phenolic compounds) of the oil. The volatile compound profiles were mainly determined to define the oxidative degree of oil and to better understand the effect of the fatty acid degradation on the organoleptic properties of oil. Unfortunately, sensory analyses were rarely performed. This review highlights a lack of knowledge on walnut sampling before oil analysis and a distortion between some results of chemical compounds. Impact of walnut variety, walnut storage and oil extraction process was documented but few studies have considered the temporal factor of harvest, the packaging and the storage conditions of oil, which influence its chemical composition and consequently its nutritional and taste qualities.Cette revue présente une synthèse complète des données sur la composition chimique de l'huile de noix (composés majeurs et mineurs) recueillies dans la littérature en fonction des variétés et des origines géographiques des noix, et des procédés d'extraction de l'huile. Considérés comme des facteurs d'influence, les paramètres de traitement avant et après récolte des noix en coque et des cerneaux ont été identifiés et les travaux sur la stabilité de l'huile ont été discutés en fonction du prétraitement des noix, des procédés d'extraction de l'huile et de leurs conditions de stockage. La plupart des études ont porté sur la quantification des acides gras et des tocophérols. La composition en triacylglycérols et les composants mineurs (stérols, volatils, composés phénoliques) de l'huile ont suscité moins d'intérêt. Les profils des composés volatils ont été déterminés principalement pour définir le degré d'oxydation de l'huile et pour mieux comprendre l'effet de la dégradation des acides gras sur les propriétés organoleptiques de l'huile. Malheureusement, les analyses sensorielles ont rarement été réalisées. Cette revue met en évidence un manque de connaissances sur l'échantillonnage des noix avant l'analyse de l'huile et une distorsion entre certains résultats des composés chimiques. L'impact de la variété de noix, du stockage des noix et du processus d'extraction de l'huile a été documenté mais peu d'études ont considéré le facteur temporel de la récolte, le conditionnement et les conditions de stockage de l'huile, qui influencent sa composition chimique et par conséquent ses qualités nutritionnelles et gustatives

Comparative study of the alignment method on experimental and simulated chromatographic data

International audienceOne of the major problems in the signal comparison of chromatographic data is the variability of response caused by instrumental drifts and others instabilities. Measures of quality control and evaluation of conformity are inherently sensitive to shift. It is essential to be able to compare test samples to reference samples in an evolutionary analytical environment by offsetting the inevitable drift. Therefore, prior to any multivariate analysis, the alignment of analytical signals is a compulsory preprocessing step. During recent years, many researchers have taken a greater interest in the study of the alignment. The present paper is an updated review on the alignment algorithms, methods, and improvements used in chromatography. The study is dedicated to one-dimensional signals. Several of the exposed methods have common theoretical bases and can differ through their optimization methods. The main issue for the operator is to choose the appropriate method according to the type of signals to be processed

Exploring the Scientific Interest for Olive Oil Origin: A Bibliometric Study from 1991 to 2018

International audienceThe authenticity and traceability of olive oils have been a growing concern over the past decades, generating numerous scientific studies. This article applies the tools of bibliometric analyses to explore the evolution and strategic orientation of the research focused on olive oil geographical and varietal origins. A corpus of 732 papers published in 178 different journals between 1991 and 2018 was considered. The most productive journals, authors and countries are highlighted, as well as the most cited articles associated with specific analytical techniques. A cluster analysis on the keywords generates 8 main themes of research, each focused on different analytical techniques or compounds of interest. A network between these thematic clusters and the main authors indicates their area of expertise. The metabolomics methods are drawing increasing interest and studies focused on the relationships between the origin and the sensory or nutritional properties provided by minor compounds of olive oils appear to be future lines of research

Comparative Study of the Effects of Thermal and Photochemical Accelerated Oxidations on Quality of “Green Type” and “Black Type” French Olive Oils

International audienceOxidative stability of two commercial olive oils of different specificity (green type and black type) has been studied during thermal and photochemical accelerated processes through the evolution of quality indices. It might help to assure a good utilisation of olive oil. In most of works described in literature, they are measured individually. In this study, a Principal Component Analysis (PCA) has been performed to emphasize their variation and describe in concise way the quality and the safety of extra-virgin olive oil after two oxidative stresses. No difference had been detected between both type oils when they are heated. Peroxides, aldehydes and conjugated dienes and trienes were formed but rapidly degraded into final oxidation compounds , mainly acid compounds. During the photochemical process, similar changes occurred slower and the green type oil had shown better stability because of its higher phenolic content. The fatty acids had been more impacted (higher disappearance of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA)) when the oils were heated than when irradiated. Saturated fatty acids (SFA), MUFA and PUFA were the most relevant indicators to characterize non-oxidized oils and PV characterized the early stage of oil oxidation

Control chart and data fusion for varietal origin discrimination: Application to olive oil

International audienceCombining data from different analytical sources could be a way to improve the performances of chemometric models by extracting the relevant and complementary information for food authentication. In this study, several data fusion strategies including concatenation (low-level), multiblock and hierarchical models (mid-level), and majority vote (high-level) are applied to near-and mid-infrared (NIR and MIR) spectral data for the varietal discrimination of olive oils from six French cultivars by partial least square discriminant analysis (PLS1-DA). The performances of the data fusion models are compared to each other and to the results obtained with NIR or MIR data alone, with a choice of chemometric pre-treatments and either an arbitrarily fixed limit or a control chart decision rule. Concatenation and hierarchical PLS1-DA fail to improve the prediction results compared to individual models, whereas weighted multiblock PLS1-DA models with the control chart approach provide a more efficient differentiation for most, but not all, of the cultivars. The high-level models using a majority vote with the control chart decision rule benefit from the complementary results of the individual NIR and MIR models leading to more consistently improved results for all cultivars

A Rheological Method to Evaluate the Physical Stability of Highly Viscous Pharmaceutical Oil-in-Water Emulsions

International audienceThe aim of this study was to develop a rheological method to evaluate the stability of highly viscous pharmaceutical emulsions. Thereby, the time devoted to the storage tests could be reduced and manufacturers could save time in optimizing their formulations and manufacturing techniques for topical pharmaceutical forms. The influence of the type of oil and the type of emulsifier on the microstructure of the emulsions was also studied. Materials and Methods. The samples were stored at 25 and at 50-C for 6 months and analysed every month using rheological as well as microscopic techniques. The size and the organization of the droplets within the emulsion were determined by freeze-fracture electron microscopy and optical contrast phase microscopy. Results. A decrease in the rheological parameters was observed for the OC emulsions (BTween/Spanê mulsions made with olive oil) and the BMontanov^emulsions. The rheological measurements showed that the structure of the OC emulsions and that of the emulsions made with the Montanov 82 emulsifier become more brittle when submitted to a shear force. The micrographs obtained by freeze-fracture electron microscopy showed that for OC only the oil droplets arrange in a network structure. Storage tests at 50-C confirmed the rheological assumptions on the stability of emulsions. Conclusion. The study of the effect of shearing on the emulsions allowed quick discrimination between the emulsions according to their stabilities. The rheological tool gave information on the structure of the emulsions and on the aging process

NIR PLS prediction of quality parameters of olive oils at different stage of ageing

International audienceThe chemical composition of olive oil depends on olive variety, climatic conditions during growth and olive maturity. There are mainly composed of triglycerides (95 to 98%) and minor compounds include phenolic compounds, tocopherols, alcools, esters, hydrocarbons, and pigments (Cert, Moreda, & Pérez-Camino, 2000). The nutritional and health benefits of olive oil can be attributed to antioxidants (phenolic compounds and tocopherols) and to the fatty acid composition of triglycerides: an abundance of monounsaturated fatty acid (MUFA), namely oleic acid, compared to saturated fatty acids (SFA) and an appropriate presence of polyunsaturated fatty acids (PUFA) especially ω6 and ω3 essential fatty acids. This leads to a good influence on cardiovascular diseases and cellular ageing (López-Miranda et al., 2010). But unsaturated lipids are particularly susceptible to oxidative phenomena that occur during cooking processing and storage. A series of reactions such as hydrolysis, oxidation, polymerisation, isomerisation and cyclisation (at 180°C or above) (Gertz, Klostermann, & Kochhar, 2000) may occur and lead first to the formation of peroxides and hydroperoxides, instable products that may involved into secondary oxidative products as hydrocarbons, alcohols, aldehydes and ketones which may also be oxidized in carboxylic acids (Gertz et al., 2000). Oxidized oil will have a less nutritional interest than a well conserved oil (Frankel, 1984).To estimate the oil quality, the international oleic council (IOC) and the international standardisation organisation (ISO) recommend to measure peroxide value (PV) (ISO 3960, 2007), spectroscopic indexes (K232 and K270) (International Olive Council, 2001a) the p-anisidine value (AV) (ISO TC34/SC 11, 2003), free acidity (FA) (ISO 660, 2009) and fatty acid composition by chromatographic analyse (International Olive Council, 2001b). PV, often used to evaluate the degree of oxidation, measures the amount of total peroxides. It increases at the beginning of the oxidation process and then decreases, because peroxides are transient chemical compounds. Its evolution depending on the heating time and temperature, is related to the antioxidant concentration of oil (Bešter, Butinar, Bučar-Miklavčič, & Golob, 2008; Nissiotis & Tasioula-Margari, 2002). K232 and K270 indexes measure the specific absorbance at 232 and 270 nm respectively of the conjugated dienes and trienes formed in autooxidation process from the hydropreroxides of unsaturated fatty acids and their oxidation products (Pristouri, Badeka, & Kontominas, 2010; Shahidi & Wanasundara, 2002). AV provides a good estimation of aldehydes especially conjugated dienals and 2-alkenals, main secondary oxidation compounds (Shahidi & Zhong, 2005), and completes the PV determination (Casal, Malheiro, Sendas, Oliveira, & Pereira, 2010). The total oxidation value (TOTOX = 2 PV + AV) gives a better estimation of the progressive oxidative deterioration of fats and oils because it measures both hydroperoxides and their breakdown products, i.e. aldehydes (Poulli, Mousdis, & Georgiou, 2009). Determination of fatty acids composition (which constitute the triacylglycerols) allows to follow their evolution individually (Bešter et al., 2008 ; Bouaziz, Fki, Jemai, Ayadi, & Sayadi, 2008) or grouped in class (SFA, MUFA and PUFA) (Casal et al., 2010; Maggio et al., 2009).In this work, two oils were studied because of their own method of manufacture, which is supposed to induce a difference in oil composition. Knowing that the degradation rate of olive oil was influenced by temperature, light, presence of oxygen and storage time, the aim was to study the stability of oils stored in different conditions of light, temperature and oxygen supply, via the determination of the quality indices and to evaluate the combined effects of these storage parameters. , Fourier transform infrared (FT-IR) spectroscopy has become an emerging well-accepted analytical technique, due to its simplicity with advantages in terms of cost per sample. It achieves high analysis speed and requires little or no sample preparation. FT-IR spectroscopy has been widely used as an analytical tool in various laboratories and industrial sectors such as food agricultural, petrochemical, textual and pharmaceutical. Up to date, a lot of studies have been published on the utilization of Near and Mid FT-IR for authentication, identification or classification of many agro-foods, notably olive oils (Casale et al., 2010a; Dupuy et al., 2010b; Galtier et al., 2007; Sinelli et al., 2010) and table olives (Casale et al., 2010b; Dupuy et al., 2010a) by multivariate statistical analysis of spectral data. Near FT-IR (FT-NIR) has been applied on olive leaves to discriminate between the juvenile and adult leaves (Leon & Downey, 2006) and for prediction of nutritive composition (Fernandez-Cabanas, Garrido-Varo, Delgado-Pertinez & Gomez-Cabrera, 2008). The present work investigates this methodology for two olive oils aged under different storage conditions

Discrimination of extra virgin olive oils from five French cultivars: En route to a control chart approach

International audienceThe control of varietal origin is an important issue to insure the authenticity of olive oils. In this study, extra virgin olive oils from five French cultivars were discriminated by applying partial least square discriminant analysis (PLS1-DA) to their fatty acid and squalene compositions obtained by gas chromatography. Two decision rules were compared to determine the varietal origin of predicted samples: either a classical PLS-DA approach with uncertainty zones, or a control chart approach with warning and control limits. The control chart approach, being focused on characteristic samples from each modelled cultivar, is able to deal with classes having unbalanced number of samples and to identify atypical samples

Composition and authentication of virgin olive oil from French PDO regions by chemometric treatment of Raman spectra

International audienceThe search for the origin and the authentication of virgin olive oils (VOOs) is a problem of topical interest. VOOs with the protected designation of origin (PDO) label can be subject to fraudulent practices owing to high price commanded by these oils. This work evaluates the capability of confocal Raman spectroscopy combined with chemometric treatments for determining the fatty acid and triacylglycerol (TAG) compositions of VOOs and for authenticating the PDO labels of six French VOOs. Fatty acid and TAG compositions were determined by chemometric analysis of the Raman spectra using the partial least square (PLS) algorithms. Predictions have provided good results on the high percentage compounds, but for the fatty acids at very low percentages the predicted results were very poor. The PLS-discriminant analysis model on Raman spectra was able to correctly classify 92.3% of French PDOs and 100% of PDO samples made with only one principal cultivar. However, it was noticeable that the first regression coefficient (which explains the greatest amount of variation of the data) obtained for each PDO could be compared one by one with the first regression coefficient obtained for the quantitative analysis of fatty acids and TAGs. The first regression coefficients obtained for PDOs differed widely from each other. Their study allowed interpreting the PDOs according to their chemical composition. This work confirms that fatty acid and TAG percentages may be used to authenticate French VOOs into PDO