Chemical and physical analysis for food products

12 Juillet 2012, BrestChemical and physicalanalysis forfood productsPhilippe Mongondryp.mongondry@groupe-esa.com1

Techniques for food products: what for?Quality controlQuantification of nutriments, vitaminsof compoundsIdentification of contaminationDetermination of ingredientsAuthentication of origin of the product2

Foodstuffs should not contain micro-organisms or theirtoxins or metabolites in quantities that present anunacceptable risk for human health.(EC Rule No 2073/2005)3

Many analytical chemical and physical techniques:Electro-analysis Q ty of ions Gravimetry Fat or water contentElectrophoresis separation Atomic spectrometry trace elementMolecular spectrometry emission (Fluo); diffusion (Raman) absorption (UV, IR RMN)Mass SpectrometryRadiometry ( 14 C) origin & dateX ray diffusion structural ID Rheometry Flow & structureSensory analysisChromatography4

Preparation of sample for analysis is critical !!HomogeneisationSolubilisationSeparationAnalysis5

Physical and chemical analysis• Chromatography• Spectroscopy and relatedmicroscopies (UV – visible – IR)• SNIF NMR and Mass spectrometrySensory analysis• Concepts and Basis6

Chromatography or HPLCExtraction and preparationin liquid mediaSeparation & Identification7

Chromatography or HPLCHigh Performance Liquid ChromatographyDifferent Types• Partition chromatography• Normal-phase chromatography• Reversed-phase chromatography (RPC)• Size-exclusion chromatography (SEC)• Ion-exchange chromatography• Bio-affinity chromatographySEC8

Chromatogram ofpesticide in cow milkIdentification ofpolyphenols in wine byUV detectors with HPLC9

MatterSpectroscopyand interactions10

interactions light/matterfluorescencediffusionphotoemissionphotontransmissionabsorptionEJ )h. ( Hz)h hc( m( m)h : constante Planck; h= 6,62 x10 -34 J.s -1( 1c)diffraction

From atom to complex molecules12

Biological Molecules• Thousands of different molecules per cell, fast Renew•Complex systemBiological specificity with 'allowed' movement andconformation• E(link etc...)reactions, biological and thermodynamicparameters• Particularity :transformation of light energy (chlorophyll)ProteinsGlucideLipidsNucleic acid13

Spectroscopic principleselectromagnetic radiancedomainRadiofrequencyMicro-ondesNuclear Magnetic ResonanceNuclear Quadrupole ResonanceElectronic paramagnetic Resonancemolecular rotations spectrumPhenomena Frequency (Hz) Wave length10 6 to 10 8 300 to 3 m10 10 to 10 12 300 to 0.3 mmInfrared molecular vibrations 10 12 to 3 10 14 300 to 0,8 mVisible and ultraviolet Electronic Transitions (external e-) 3 10 14 to 10 16 800 to 10 nmX Rays Electronic Transitions (core e-) 3 10 16 to 10 19 10 to 0.03 nmRays nuclear Transitions 10 19 to 10 220.03 to 0.003nm14

From Far infrared to X-rays…

Spectroscopic principlesEmission of large spectrum of photons (energy)Transmission and reflection = nothingAbsorption of energyUV absorption spectrumPowerful photons No! but right ones Yes! 16

Spectroscopic principlesConstruction of absorption spectrumPolychromatic radiationIIAbsLarge spectre of thesourceSpectrale compositionof transmise light17

Spectroscopy UV-visibleHOAbsorption of UV by unsaturated bondsOYESYESONH 2NOYESOQuantitative method,Kinetic of reaction…18

Infrared SpectroscopyPrincipe:Molecule under infrared radiation: vibration and rotationSymmetricalstretchingRockingWaggingAntisymmetricalstretchingScissoringTwistinghttp://fr.wikipedia.org/wiki/Spectroscopie_infrarouge19

interactions light/matterAtomic/molecules linkage movements due to which wave lengths in IR?~3.3 m3756 cm-1 3652 cm-1 1595 cm-1~6 m ~10 m ~30 m

Fourier Transform InfraRed SpectroscopyFingerprint of moleculesspectrometer FTIRUsed for samples :Gaz, liquid or solid in powder21

Quanti fy nutritional compounds by FTIR : polyphenols in apple22

Quanti fy the quality of fruits by fast method : NIRFTIR spectrum related to°Brix, pH, dried matteror starch content,maturity, defaults…1.5Sucres1+R11BOHR 2Sucres1932S. Bureau, INRA Avignon0.50-0.5HO-1-1.5Anthocyanes 450AROHChlorophylle 553120012706759767751455Am2P3Am1P3At0P3At1P3At2P3At3P3At4P3At5P3At6P3500 1000 1500 2000 2500Longueurs d’onde (nm)23

Quanti fy the quality of fruits by fast method : Ex. in appleTotal acidRefractometricindex24

Log(1/R)IR microscopy = spatialchemical distribution50 m1.11.00.90.8DNALipidsProteins0.70.65 m0.5DNAProteinsLipidsSections congelées (6µm) de muqueuse intestinale humaineM-P. Bralet and F. Le Naour, INSERM U775Hôpital Européen Georges Pompidou, Paris;0.40.30.20.135003000 2500 2000 1500Wavenumbers (cm-1)1000

Quanti fy the quality of milk by fast method : FTIR•Le Milkoscan FT 120 de Foss : Fat, proteins, extrait sec content,proteins•Based on more than 15 years database to calibrate the apparatusMuch faster than standard chemical analysis of reference

Biocristallography with X-raysCristal of proteinDiffracted rays3) recording X-raysimagegoniometer1) cristalRayons X2) diffraction3D Structure of enzymeRNA Polymerase II4) Rebuilding 3D structure

Few examples of microscopiesStudy of resistant bacteria by UVIn situ study of diffusion of antibiotic,through bactéria membrane (first stepresistance to antibiotics).Study of fermentation and cookingof bread (bubbles of CO2) by X-rays microtomography

SNIF NMR Site-Specific Natural Isotope Fractionation Nuclear Magnetic ResonanceBased on the absorption of deuterium in plants (Glucose or ethanol)Irregular distribution of De on the Earth due to rotationAddition of different type of sugar in Tequilas29

Mass SpectrometryMain steps of the measurementAimsDetermination of the molecularweight of big molecules (proteins)Quick Identification based ondatabasesUnknown sample30

Mass SpectrometryIdentificationReconstruction by affinity of piecesDepend on position of the picks and ratio m/ZCoupling HPLC-MSCoupling techniques is powerful !!31

Sensory analysisWhat consumer understand from different information we give him ?How his sensory experiments is influenced by the information he has ?What is the impact of a new process or technology on his fondness ?What is important in his purchase behavior ?How to measure the sensory performance of products ?How improve his loyalty ?What consumer looks for ?What does he discern in products ?32

Sensory analysisHow objectively measure the tasting and thesensorial characteristics of food products?Factors which influence the choice of a food product ( Gains, 1994)Consumer Context productHabitsCulturePersonalityCurrent moodPhysiology (allergy)Time of the dayplaceWith whohowWhy whatSensorial characteristicsNutrimentsPackaging33

Sensory analysis of Food productsDefinition:Evaluation of organoleptic properties of a food product by human sensesbased on experimental design and statistical analysis (combination ofinferences or deductive reasoning and insight or specific cause and effect)ICS 67.240 Sensory analysis(ISO standard)Glossary34

Sensory analysisHow objectively measure the tasting and the sensorial characteristics of food products?3 categories: Effective, affective and perception analysisdifferences preferences Evocations MotivationsDescriptiveTestHedonicTestQualitativeTestTrained panelNaive consumers35

Sensory analysisStudy consumer behavior and motivationto get a better understanding of his reactionsAims: Identify all reactions, all opinions that consumer haveExample : Reaction in front of the product• Label, design• Information• Price• Association of these different attributesWhich cap do you prefer ??36

Thank you for your attentionp.mongondry@groupe-esa.com37