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analytikLtd
Multispectral Imaging of Food Quality
Rapid Non-destructive Surface Analysis
Adrian Waltho, Analytik Ltd (Cambridge, UK)
www.analytik.co.uk/multispectral-imaging
• Light reflectance at separate colours
• Statistical image processing
• Chemical, physical and spatial properties
• Differentiate | Quantify | Report
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Traditional colour imaging uses three broad bands of colour:
Red, Green and Blue
Normal Colour Imaging
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Normal Colour Imaging
• RGB photographs have limited spectral resolution
• Chlorophyll a and b give almost the same RGB signal and are not spectrally separated
Chloro-a High Low High
Chloro-b High Low High
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Multispectral Imaging
Chloro-a High Low Low High
Chloro-b Med High Med Low
• Using just 4 wavelength bands with tightly defined ranges, Chlorophyll a and b can easily be distinguished
• VideometerLab 3 uses 19 wavelength bands
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Multispectral Imaging
• Many images obtained at selective wavelength bands
• Each image pixel contains spectral data points
• Spectral signature reveals chemo-specific information
• See spatial location of surface chemical variation
Ultraviolet Near-Infrared
Infra-Red Red Yellow Green Blue Ultra-Violet
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VideometerLab 3 Schematic • Narrowband illumination by 19
LEDs at points between 375nm-970nm (UV-Vis-VNIR), strobing sequentially with precise time control for known light output
• Integrating sphere diffuses light onto sample from all angles
• 5 mega-pixel monochrome CCD camera captures % reflectance at each LED wavelength for each image pixel, NIST calibration
• Optional Emission filter wheel for fluorescence detection and Bright-field or Dark-field back lighting
Camera
LEDs
Integrating
sphere
Emission
filter
wheel
Sample
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VideometerLab 3 Schematic • Precise control at each separate
point of the 375-970nm spectrum, only possible with LEDs, allows optimal illumination for best signal to noise
• Provides calibrated data, suitable for statistical analysis and manipulation for discovery
• Emission filters allow additional multispectral fluorescence imaging, with excitation at each LED wavelength
• Powerful, user-friendly hardware setup and image analysis software is central to the system
Camera
LEDs
Integrating
sphere
Emission
filter
wheel
Sample
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VideometerLab 3 Schematic
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Index of application areas
1. Sorting \ Categorising 1. Seafood sorting
2. Product composition
3. Pork fat percentage
2. Spoiling 1. Meat spoilage
2. Meat browning
3. Fruit oxidising
4. Biscuit burning
3. Quality Control 1. Seed contamination
2. Biscuit mishandling
3. Counterfeit packaging
www.analytik.co.uk
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Sorting Seafood Sorting
Back to Index 5
• The traditional method of assessing salmon colouration is to use a colour chart.
A human operator will offer his or her ‘best guess’ as to the colour of the salmon
This salmon is a 27 on the
SalmoFan chart opposite.
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Sorting Seafood Sorting
Back to Index 5
• The VideometerLab can be taught two extremes of salmon colouration, and
then will false colour an image to represent what it has just learned (blue is the
‘pinkest’ a salmon can ever be, orange is the ‘reddest’)
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Sorting Seafood Sorting
Back to Index 5
• It can then apply this model to a real salmon, and will not make any of the
mistakes the traditional methods will
Colour in RGB False Colour Image
(Human Vision) (Videometer ‘Vision’)
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Sorting Seafood Sorting
Back to Index 5
• Most usefully, a salmon that does not fall neatly onto an integer number can
have its colour determined with up to two decimal places of accuracy
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Sorting Seafood Sorting
Back to Index 5
• Prawn sorting is done in the same way, with the same sorts of subjectivity
problems, compounded by the fact there are many hundreds of prawns to be
analysed at any one time
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Sorting Seafood Sorting
Back to Index 5
• The VideometerLab can separate touching prawns and automatically put them
in the correct ‘bin’ to guide an operator later. In this image the VideometerLab
has automatically ignored anything too small to be a prawn
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Sorting Product Composition
Back to Index 5
• In this image the operator wants to identify what percentage of this tuna steak is
blood meat
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Sorting Product Composition
Back to Index 5
• The operator can either highlight the difference between blood meat on the left
and other meat on the right and measure it with the onboard geometry tools or
skip out the human element altogether and quantify the percentage
automatically, as in the right-hand image
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Sorting Product Composition
Back to Index 5
• Similar techniques can be used on most heterogeneous substances, such as
the morceau in this foix gras
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Sorting Pork Fat Percentage
Back to Index
• The VideometerLab can quantify the percentage of fat in this minced pork
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Sorting Pork Fat Percentage
Back to Index
• It does this by learning the spectral signature of fat and pork, then correlating the two
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Sorting Pork Fat Percentage
Back to Index
• In this experiment the VideometerLab performs excellently – it is always within 0.5% of the chemical test’s predictions
Vid
eo
mete
rLa
b %
Estim
ate
Chemical Analysis % Fat
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Spoiling Meat Spoilage
Back to Index
• The VideometerLab can be used for a variety of meat spoilage tests – here is one example looking for the number of bacterial colonies and discolouration of some mince after storage under different conditions
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Spoiling Meat Spoilage
Back to Index
• These images show just the UV (405nm) band to better highlight the size and distribution of the bacterial colonies
No special storage Atmospheric Packaging M.A.P.
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Spoiling Meat Spoilage
Back to Index
• This histogram demonstrates quantitatively what is visually apparent on the last slide – MAP reduces the incidence and size of bacterial colonies
• Sample 1 before storage
• Sample 1 after atmospheric
storage
• Sample 2 before storage
• Sample 2 after MAP storage
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Spoiling Meat Discolouration
Back to Index
• Alternatively, it can be used to predict browning, as with this sample of steak – the blue area shows higher levels of metmyoglobin which appears to predict discolouration
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Spoiling Fruit Oxidising
Back to Index
• The VideometerLab can be used as an objective measure of food spoilage
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Spoiling Fruit Oxidising
Back to Index
• The blue areas are browning, the red areas are unaffected. This can be quantified automatically by the VideometerLab software
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Spoiling Fruit Oxidising
Back to Index
• The VideometerLab can capture the whole browning process
1 5 10
15 20
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Spoiling Biscuit Burning
Back to Index
• In this slide the operator has taken a spectrum of the corner of each of these biscuits, and proved that the ‘blue’ biscuit (top left) has been burned during cooking
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QC Seed Contamination
Back to Index
• A human operator would be hard pushed to notice the single poppy seed contaminating this dish of sesame seeds. This could be fatal if instead of poppy seed it were a fragment of peanut, for example
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QC Seed Contamination
Back to Index
• Magnification of the previous image
1mm
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QC Biscuit Mishandling
Back to Index
• An operator handling this biscuit with wet fingers will spoil the taste, but may be difficult to spot if it is unexpected
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Multispectral Image Analysis
• A variety of image processing tools are available in VideometerLab’s analysis software
• Analysis protocols and models can be saved and applied to new samples for routine analysis
• Multiple analysis models can be run on the same image data to quantify separate parameters
• Analysis can be batch-run to aid in high-throughput data acquisition
• Image archiving provides a record of samples for future data mining and regulatory compliance
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• Nuanced, human-like analysis of heterogeneous samples
• Objective, accurate, repeatable measurements
• Non-destructive analysis allows further sample assay work
• No sample preparation is required
• Rapid data acquisition and analysis enables high throughput screening
Why use Multispectral Imaging?
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• Hardware options
• Emission filter wheel (4 x 25mm Ø) for fluorescence macro-imaging
• Dark- or Bright-field backlighting for scattering or translucency analysis
• Bespoke solutions available
• Software options
• Image Processing Toolbox for filtering and segmentation of image data in individual spectral bands
• Multispectral Imaging Toolbox for multivariate image analysis and modelling
• Blob Toolbox for granular object separation, analysis and data output reporting
• Matlab multispectral imaging toolbox integration
Hardware and Software Options
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• Nuanced, human-like analysis of heterogeneous samples
• Sophisticated data analysis tools for the novice and power user
• Objective, repeatable data collection with easy export
• Rapid, non-destructive testing with no sample preparation
VL3 Multispectral Imaging
Multispectral imaging at Analytik.co.uk
VL3 Datasheet PDF
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