Presentation on theme: "The Queens University of Belfast Supervisors: Dr SEJ Bell Dr BW Moss Potential Applications of Raman Spectroscopy in Predicting Meat Quality René Beattie."— Presentation transcript:
The Queens University of Belfast Supervisors: Dr SEJ Bell Dr BW Moss Potential Applications of Raman Spectroscopy in Predicting Meat Quality René Beattie
Roskilde, August, 2001. Introduction to resonance Raman spectroscopyIntroduction to resonance Raman spectroscopy Introduction to Raman spectroscopyIntroduction to Raman spectroscopy Comparison with NIRComparison with NIR Previous work on Raman spectroscopy of meatPrevious work on Raman spectroscopy of meat Current research:Current research: Initial work on lipids – model systems Initial work on lipids – model systems Meat lipids – adipose and intramuscular fat Meat lipids – adipose and intramuscular fat Aspects of meat quality – cooking and ageing Aspects of meat quality – cooking and ageing Future plans and potential for RamanFuture plans and potential for Raman
Raman Spectroscopy Irradiate sample with monochromatic radiation h h h h h h h Collect inelastically scattered light Rayleigh Intensity 0 Frequency difference gives vibrational spectrum
Weak effect Advantages Minimal sample prep. Disadvantages Very general Rich in information Aqueous samples Special techniques Expensive Experimentally difficult Fluorescence interferes
Diode lasers:Diode lasers: Wide range of wavelengths and also tunable lasers to allow increased flexibility. Low-Cost, Compact Raman Spectrometers Enabling Technologies Notch filter:Notch filter: Eliminate the strong laser line, preventing detector saturation. CCDs (Charge Coupled Detectors):CCDs (Charge Coupled Detectors): Ultra high quantum efficiency detectors for detection of very low levels of light. >$100k ~$10k $60k
Schematic layout diagram for the CCD system Holographic Notch Filter Spectrograph C.C.D. Depolariser Sample Diffraction Grating Telescope Ar + Ti-Saph Lasers =785nm
Raman Techniques: Dispersive Raman Spectroscopy In food analysis fluorescence and expense are the major problems. FT Raman spectroscopy overcomes fluorescence, but at an even higher cost. Radiation on the boundary of visible and near-infrared radiation: Most basic form of Raman spectroscopy: UV/ Visible radiation – use conventional optics and detection equipment Uses conventional visible optical equipment Reduces fluorescence Cheaper
Comparison of NIR & Raman Spectroscopy:- principles of measurement principles of measurement Near Infrared ReflectanceRaman Spectroscopy Non Destructive Spectroscopic Molecular Vibrations + Electronic Configuration Molecular Vibrations Difficult to assign peaksAssignable peaks Particle size + Physical StatePhysical State Large water effectLow water interference
Comparison of NIR & Raman Spectroscopy:- Practical Aspects Practical Aspects Near Infrared ReflectanceRaman Spectroscopy Large area of measurementSmall area of measurement Fibre optic system Compact systems User friendly Cost £30k upwards* * This price is for a general purpose bench-top instrument, rather than smaller task orientated devices
Foodstuffs Sample preparation frequently requiredSample preparation frequently required Main food groups all give spectraMain food groups all give spectra Wavenumber (cm -1 ) 180014001000600 11001300150017001900210023002500 Wavelength (nm) Carbohydrate Protein Fat RamanNIR No sample preparationNo sample preparation Main food groups all give detailed spectraMain food groups all give detailed spectra Absorbance Raman Intensity
Wavenumber (cm -1 ) 180014001000600 11001300150017001900210023002500 Wavelength (nm) Absorbance Raman Intensity Protein Water Comparison of NIR and Raman Spectra of Protein
Problems Encountered in Literature Background: Not part of the Raman Signal – generally should be removed Signal Intensity: Absolute intensity hard to control – need internal standard Glass – not suitable for NIR excitation (>700nm) Fluorescence, elastic light scattering, absorption and other photon emitting processes Depends on exact focal position, laser power, notch tuning, sample absorption and system alignment.
Current Research Model Lipids:Chain length Unsaturation Level cis/trans isomerisation Physical State Adipose Tissue: Speciation Correlation with GC data Composition variation within sample Meat:Ageing Cooking Pressure Treatment Intramuscular Fat Sensory panels
-8000 -6000 -4000 -2000 0 2000 4000 6000 8000 10000 -8000-6000-4000-200002000400060008000 u t PLS Analysis of Lamb Adipose Data
Unsaturation Profile of pork adipose tissue 0.29 0.3 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 02000400060008000100001200014000 depth/ m Unsaturation Level / Raman band ratio
Previous Raman Work Whole Muscle: Spectra dominated by myosin (main component).Spectra dominated by myosin (main component). Water Content.Water Content. Intact single fibers: Again dominated by myosin.Again dominated by myosin. Contraction had little effect.Contraction had little effect. Ions affected individual amino acids.Ions affected individual amino acids. Isolated proteins: Effect of different conditions (pH, salts and temperature) on protein structure.Effect of different conditions (pH, salts and temperature) on protein structure. All major proteins in meat.All major proteins in meat.
Raman spectra of the main components of meat Raman Shift / cm -1 Raman Intensity 600600 Protein 100014001800
The fine structure of skeletal muscle and meat Z Line A Band I Band M Line Myosin Actin H Zone
6001400120010008001600 Raman Shift cm -1 Effect of Ageing on the Raman Spectrum of Meat 1 Day Projected Residual 11 Days Difference TyrSkeletalMetCysCH 2 scAmide III (C-N) Amide I helix -sheet
-100 -80 -60 -40 -20 0 20 40 60 80 100 -1000100 t t Day 1 Day 4 Day 11 Day 8 Principal Component Analysis of the Raman spectra of Pork as it is aged
-100 -50 0 50 100 -1000100 t t Day 1 Day 4 Day 11 Day 8 PLS Disriminant Analysis of the Raman spectra of Pork as it is aged
-0.10 0.00 0.10 w*c 0.000 0.040 0.080 0.120 0.160 w*c -0.050 0.000 0.050 0.100 0.150 w*c 0100200300400500 NUM Weightings for PLS Disriminant Analysis of the Raman spectra of Pork as it is aged Component 1: Average (unscaled normalised data) amide hydrolysis and residue effects Component 2: amide hydrolysis and residue effects secondary structure and residue shifts Component 3: secondary structure and residue shifts
-100 -50 0 50 100 -100-80-60-40-20020406080100120140160 u t Day 1 Day 4 Day 11 Day 8 PLS of the Raman spectra of Pork as it is aged – Component 2, proteolysis
Effect of Cooking on Components of Beef Relative Intensity Raman Shift / cm -1 650650900 Protein 1750 1500 1200
Possible Plans for Meat Research: Possible Plans for Meat Research: Speciation of meat (by muscle and/or fat).Speciation of meat (by muscle and/or fat). Cold shortening – contraction of meat.Cold shortening – contraction of meat. Tenderness – state of contraction, hydrolysis of proteins etc.Tenderness – state of contraction, hydrolysis of proteins etc. Taste – can Raman predict which pieces of meat taste good?Taste – can Raman predict which pieces of meat taste good? Final internal temperature of cooked meats.Final internal temperature of cooked meats. Fatty Acid composition – incorporate work on lipids.Fatty Acid composition – incorporate work on lipids. Investigate applications for Resonance RamanInvestigate applications for Resonance Raman Raman spectra will be compared to standard tests and to taste tests
The future of Raman Meat Quality Attributes Instrumental/Rapid Method AppearanceFlavourTextureReflectance Electronic nose +Raman? NIR? Raman? Nutritional Quality Proximate Analysis Characterisation:-Lipid Protein/Amino Acids Carbohydrates NIR? Raman? RamanRaman?Raman?
Conclusions Raman is a powerful probe of the structure of the protein and fat within meat. Raman is a powerful probe of the structure of the protein and fat within meat. Raman can be used to investigate the extent and process of proteolysis.Raman can be used to investigate the extent and process of proteolysis. Analysis underway to correlate Raman data with :Analysis underway to correlate Raman data with : o fat content o time of cooking o processing treatment. o tenderness
My supervisors: Dr SEJ Bell and Dr BW Moss Lab Mates: Clare, Antionette, Monica, Lyndsay, Kate, Roma, Colin, Steve, Andrew, Philip and Fiona. Technical help: Alan, Colum, Griff and Ernie ? Institute? Funding: DARD (NI) Acknowledgements
Resonance Raman Spectroscopy Increases the probability of change in vibrational state before energy is released. h h h h h h Excite the particular bond involved in the adsorption to give longer lived excited state. Excitation max Irradiate sample with monochromatic radiation corresponding to adsorption band in UV-Vis spectrum h Chromophore Bands associated with this adsorption are enhanced by a factor of ~10 3 to 10 4 relative to the ground state Raman and Rayleigh. Rayleigh Intensity 0 Non-Resonance Raman Resonance Raman
Applications of Resonance Raman Spectroscopy Resonance Raman spectroscopy (RRS) probes particular bonds (chromophores) resulting in: Very precise information about specific bonds. Detection of very low concentrations of the chromophore (less than 10 -6 M). Detection of very small changes in the chromophore. This is useful for meat analysis because: The amide bond of meat is a chromophore and has a well established relationship with the secondary and tertiary structure of the protein. RRS can improve analysis of changes in amide bonding hence structure of the protein or level of proteolysis.