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analytikLtd

Multispectral Imaging of Food Quality

Rapid Non-destructive Surface Analysis

Adrian Waltho, Analytik Ltd (Cambridge, UK)

adrian.waltho@analytik.co.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

adrian.waltho@analytik.co.uk

Multispectral imaging at Analytik.co.uk

VL3 Datasheet PDF