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PubMed | University of Bordeaux 1, EBSI Team and Service Communications des Laboratoires
Type: Evaluation Studies | Journal: Analytical and bioanalytical chemistry | Year: 2015

The potential of wine (13)C isotope composition ((13)C) is presented to assess vine water status during grape ripening. Measurements of (13)C have been performed on a set of 32 authentic wines and their ethanol recovered after distillation. The data, obtained by isotope ratio monitoring by mass spectrometry coupled to an elemental analyser (irm-EA/MS), show a high correlation between (13)C of the bulk wine and its ethanol, indicating that the distillation step is not necessary when the wine has not been submitted to any oenological treatment. Therefore, the ethanol/wine (13)C correlation can be used as an indicator of possible enrichment of the grape must or the wine with exogenous organic compounds. Wine ethanol (13)C is correlated to predawn leaf water potential (R(2)=0.69), indicating that this parameter can be used as an indicator of vine water status. Position-specific (13)C analysis (PSIA) of ethanol extracted from wine, performed by isotope ratio monitoring by nuclear magnetic resonance (irm-(13)C NMR), confirmed the non-homogenous repartition of (13)C on ethanol skeleton. It is the (13)C of the methylene group of ethanol, compared to the methyl moiety, which is the most correlated to predawn leaf water potential, indicating that a phase of photorespiration of the vine during water stress period is most probably occurring due to stomata closure. However, position-specific (13)C analysis by irm-(13)C NMR does not offer a greater precision in the assessment of vine water status compared to direct measurement of (13)C on bulk wine by irm-EA/MS.


PubMed | Scientific Institute of Public Health WIV ISP and Service Communications des Laboratoires
Type: | Journal: BMC biotechnology | Year: 2015

Recently, the presence of an unauthorized genetically modified (GM) Bacillus subtilis bacterium overproducing vitamin B2 in a feed additive was notified by the Rapid Alert System for Food and Feed (RASFF). This has demonstrated that a contamination by a GM micro-organism (GMM) may occur in feed additives and has confronted for the first time,the enforcement laboratories with this type of RASFF. As no sequence information of this GMM nor any specific detection or identification method was available, Next GenerationSequencing (NGS) was used to generate sequence information. However, NGS data analysis often requires appropriate tools, involving bioinformatics expertise which is not alwayspresent in the average enforcement laboratory. This hampers the use of this technology to rapidly obtain critical sequence information in order to be able to develop a specific qPCRdetection method.Data generated by NGS were exploited using a simple BLAST approach. A TaqMan qPCR method was developed and tested on isolated bacterial strains and on the feed additive directly.In this study, a very simple strategy based on the common BLAST tools that can be used by any enforcement lab without profound bioinformatics expertise, was successfully used toanalyse the B. subtilis data generated by NGS. The results were used to design and assess a new TaqMan qPCR method, specifically detecting this GM vitamin B2 overproducing bacterium. The method complies with EU critical performance parameters for specificity, sensitivity, PCR efficiency and repeatability. The VitB2-UGM method also could detect the B. subtilis strain in genomic DNA extracted from the feed additive, without prior culturing step.The proposed method, provides a crucial tool for specifically and rapidly identifying this unauthorized GM bacterium in food and feed additives by enforcement laboratories. Moreover, this work can be seen as a case study to substantiate how the use of NGS data can offer an added value to easily gain access to sequence information needed to develop qPCR methods to detect unknown andunauthorized GMO in food and feed.


Hubert P.,In2P3 And University Of Bordeaux | Pravikoff M.S.,In2P3 And University Of Bordeaux | Gaye J.,Service Communications des Laboratoires
Journal of Environmental Radioactivity | Year: 2015

To control the authenticity of an old wine without opening the bottle, we developed a few years ago a method based on the measurement of the 137Cs activity. However, for recent vintages, the 137Cs activity drops to far too low values (most of the time less than 10mBq/L for a 10-year-old wine) for this method to perform correctly. In this paper we examine the possibility to date wines using the natural radio-element 210Pb which has a 22-year period. This new method we propose implies the opening of the bottle and the follow-on destruction of the wine itself, which means that it can only be used for investigating non-expensive bottles or wine lots where there are multiple bottles of the same provenance. Uncertainties on the resulting 210Pb radioactivity values are large, up to more than 50%, mainly due to local atmospheric variations, which prevents us to carry out precise dating. However it can be used to discriminate between an old wine (pre-1952) and a young wine (past-1990), an information that cannot be obtained with the other techniques based on other isotopes (137Cs, 14C or tritium). •We correlate the measured 210Pb activity in wine to the vintage year.•A precise dating with 210Pb is still difficult.•The method is complementary to the 137Cs technique we previously developed. © 2015 Elsevier Ltd.


PubMed | CNRS Institute of Molecular Sciences, CNRS Oenologie Research Unit and Service Communications des Laboratoires
Type: | Journal: Food chemistry | Year: 2015

The feasibility of exploiting Raman scattering to analyze white wines has been investigated using 3 different wavelengths of the incoming laser radiation in the near-UV (325 nm), visible (532 nm) and near infrared (785 nm). To help in the interpretation of the Raman spectra, the absorption properties in the UV-visible range of two wine samples as well as their laser induced fluorescence have also been investigated. Thanks to the strong intensity enhancement of the Raman scattered light due to electronic resonance with 325 nm laser excitation, hydroxycinnamic acids may be detected and analyzed selectively. Fructose and glucose may also be easily detected below ca. 1000 cm(-1). This feasibility study demonstrates the potential of the Raman spectroscopic technique for the analysis of white wines.


Rosec J.-P.,Service Communications des Laboratoires | Causse V.,Service Communications des Laboratoires | Cruz B.,Service Communications des Laboratoires | Rauzier J.,Institute Pasteur Paris | Carnat L.,Service Communications des Laboratoires
International Journal of Food Microbiology | Year: 2012

During two surveys conducted in 2008 and 2009, the culture method described in the international standard ISO/TS 21872-1 was applied to the detection of . Vibrio parahaemolyticus and . Vibrio cholerae in 112 living bivalve mollusc samples, with a chromogenic medium used in addition to the TCBS agar, as second selective isolation medium and for enumeration . of V. parahaemolyticus and . V. cholerae by surface inoculation. A PCR method for detection of these 2 . Vibrio species and the hemolysin genes . tdh and . trh, was applied in parallel. In 2009, the survey was extended to finfish fillets and crustaceans. PCR was also used for species confirmation of characteristic colonies. The identity of the PCR products, specifically targeting . V. parahaemolyticus, was checked by sequencing.Occurrence of . V. parahaemolyticus and . V. cholerae isolates in living bivalve molluscs ranged from 30.4% to 32.6% and from 1.4% to 4.7% respectively. In frozen crustaceans (2009 survey) . V. parahaemolyticus and . V. cholerae isolates were respectively found in 45% and 10% of the samples. No . V. parahaemolyticus or . V. cholerae was detected in frozen fish fillets, neither by the ISO method nor by PCR. In 2009, enteropathogenic . V. parahaemolyticus (. trh+) was isolated from 4 out of 43 oyster samples while the . trh gene was present in . V. alginolyticus strains and in samples where . V. parahaemolyticus was not detected (9 over 112 samples).The ISO method failed to isolate . V. parahaemolyticus in 44% to 53% of the living bivalve molluscs where PCR detected the . toxR gene specific of . V. parahaemolyticus (Vp-. toxR). Our results highlighted the need for a revision of the ISO/TS 21872-1 standard, at least, for analysis of living bivalve molluscs, and confirmed the increasing concern of enteropathogenic . V. parahaemolyticus in French bivalve molluscs. Enrichment at 41.5. °C was questioned and some reliable solutions for the improvement of the ISO/TS 21872-1 method, such as the PCR method for screening of positive samples and confirmation of colonies, were pointed out. © 2012 Elsevier B.V.


Gaillard L.,Service Communications des Laboratoires | Guyon F.,Service Communications des Laboratoires | Salagoity M.-H.,Service Communications des Laboratoires | Medina B.,Service Communications des Laboratoires
Food Chemistry | Year: 2013

A procedure to detect whether carbon dioxide was added to French ciders has been developed. For this purpose, an optimised and simplified method is proposed to determine 13C/12C isotope ratio of carbon dioxide (δ13C) in ciders. Three critical steps were checked: (1) influence of atmospheric CO2 remaining in the loaded vial, (2) impact of helium flush, (3) sampling speed. This study showed that atmospheric CO2 does not impact the measurement, that helium flush can lead to isotopic fractionation and finally, that a fractionation occurs only 5 h after bottle opening. The method, without any other preparation, consists in sampling 0.2 mL of cold (4 °C) cider in a vial that is passed in an ultrasonic bath for 10 min at room temperature to enhance cider de-carbonation. The headspace CO2 is then analysed using the link Multiflow ®-isotope ratio mass spectrometer. Each year, a data bank is developed by fermenting authentic apples juices in order to control cider authenticity. Over a four year span (2008-2011), the CO2 produced during the fermentation step was studied. This set of 61 authentic ciders, from various French production areas, was used to determine a δ13C value range of -22.59 ± 0.92‰ for authentic ciders CO2 bubbles. 75 commercial ciders were analysed with this method. Most of the samples analysed present a gas δ13C value in the expected range. Nevertheless, some ciders have d13C values outside the 3r limit, revealing carbonation by technical CO2. This practice is not allowed for organic, ''Controlled Appellation of Origin'' ciders and ciders specifying natural carbonation on the label. © 2013 Elsevier Ltd. All rights reserved.


Guyon F.,Service Communications des Laboratoires | Auberger P.,Service Communications des Laboratoires | Gaillard L.,Service Communications des Laboratoires | Loublanches C.,Service Communications des Laboratoires | And 4 more authors.
Food Chemistry | Year: 2014

High performance liquid chromatography linked to isotope ratio mass spectrometry via an interface allowing the chemical oxidation of organic matter (HPLC-co-IRMS) was used to simultaneously determine carbon 13 isotope ratio (δ13C) of organic acids, glucose and fructose in lime and lemon juices. Because of the significant difference between organic acids and sugars concentrations, the experimental protocol was optimised by applying a "current jump" to the IRMS device. The filament current is increased of 300 μA during elution in order to enhance IRMS sensitivity. Then, analysis were performed on 35 lemon and lime fruits from various geographical origins and squeezed in the laboratory. An overall average δ13C values of -25.40 ± 1.62‰, -23.83 ± 1.82‰ and -25.67 ± 1.72‰ is found for organic acids mixture mainly made up of citric acid, glucose and fructose, respectively. These authentic samples allowed the definition of a confidence domain to which have been confronted 30 commercial juices (24 "pure juices" and 6 coming from concentrate). Among these 30 samples, 10 present δ13C values outside the defined range revealing an added "C4" type organic acids or sugars, addition not specified on the label that is not in agreement with EU regulation. © 2013 Elsevier Ltd. All rights reserved.


Guyon F.,Service Communications des Laboratoires | Gaillard L.,Service Communications des Laboratoires | Salagoity M.-H.,Service Communications des Laboratoires | Medina B.,Service Communications des Laboratoires
Analytical and Bioanalytical Chemistry | Year: 2011

High-performance liquid chromatography linked to isotope ratio mass spectrometry (HPLC-co-IRMS) via a Liquiface© interface has been used to simultaneously determine 13C isotope ratios of glucose (G), fructose (F), glycerol (Gly) and ethanol (Eth) in sweet and semi-sweet wines. The data has been used the study of wine authenticity. For this purpose, 20 authentic wines from various French production areas and various vintages have been analyzed after dilution in pure water from 20 to 200 times according to sugar content. If the 13C isotope ratios vary according to the production area and the vintage, it appears that internal ratios of 13C isotope ratios ( R 13C) of the four compounds studied can be considered as a constant. Thus, ratios of isotope ratios are found to be 1.00∈±∈0.04 and 1.02∈±∈0.08 for R 13CG/F and R 13C Gly/Eth, respectively. Moreover, R 13C Eth/Sugar is found to be 1.15∈±∈0.10 and 1.16∈±∈0.08 for R 13C Gly/Sugar. Additions of glucose, fructose and glycerol to a reference wine show a variation of the R 13C value for a single product addition as low as 2.5 g/L -1. Eighteen commercial wines and 17 concentrated musts have been analyzed. Three wine samples are suspicious as the R 13C values are out of range indicating a sweetening treatment. Moreover, concentrated must analysis shows that 13C isotope ratio can be also used directly to determine the authenticity of the matrix. [Figure not available: see fulltext.] © 2011 Springer-Verlag.


High-performance liquid chromatography linked to isotope ratio mass spectrometry (HPLC-co-IRMS) via a Liquiface© interface has been used to simultaneously determine (13)C isotope ratios of glucose (G), fructose (F), glycerol (Gly) and ethanol (Eth) in sweet and semi-sweet wines. The data has been used the study of wine authenticity. For this purpose, 20 authentic wines from various French production areas and various vintages have been analyzed after dilution in pure water from 20 to 200 times according to sugar content. If the (13)C isotope ratios vary according to the production area and the vintage, it appears that internal ratios of (13)C isotope ratios (R((13)C)) of the four compounds studied can be considered as a constant. Thus, ratios of isotope ratios are found to be 1.00 ± 0.04 and 1.02 ± 0.08 for R((13)C(G/F)) and R((13)C(Gly/Eth)), respectively. Moreover, R((13)C(Eth/Sugar)) is found to be 1.15 ± 0.10 and 1.16 ± 0.08 for R((13)C(Gly/Sugar)). Additions of glucose, fructose and glycerol to a reference wine show a variation of the R((13)C) value for a single product addition as low as 2.5 g/L(-1). Eighteen commercial wines and 17 concentrated musts have been analyzed. Three wine samples are suspicious as the R((13)C) values are out of range indicating a sweetening treatment. Moreover, concentrated must analysis shows that (13)C isotope ratio can be also used directly to determine the authenticity of the matrix.


PubMed | Service Communications des Laboratoires
Type: Journal Article | Journal: Journal of agricultural and food chemistry | Year: 2016

This paper describes a method for the determination of 3-monochloropropane-1,2-diol and 2-monochloropropane-1,3-diol (MCPD) esters and glycidyl esters in various foodstuffs, which are isolated using microwave extraction. The next step is based on alkaline-catalyzed ester cleavage. The released glycidol is transformed into monobromopropanediol (MBPD). All compounds are derivatized in free diols (MCPD and MBPD) with phenylboronic acid and analyzed by gas chromatography-mass spectrometry (GC-MS). The method was validated for oils with a limit of quantitation (LOQ) of 0.1 mg/kg, for chips and crisps with a LOQ of 0.02 mg/kg, and for infant formula with a LOQ of 0.0025 mg/L. Recoveries of each sample were controlled by standard addition on extracts before derivatization. Quantitation was performed by the addition of isotopically labeled glycidyl and 3-monochloropropane-1,2-diol (3-MCPD) esters.

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