food quality evaluation techniques beyond the visible spectrum murat balaban professor, and chair of...
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Food Quality Evaluation Techniques Beyond the Visible Spectrum
Murat BalabanProfessor, and Chair of Food Process Engineering
Chemical and Materials Engineering Department
University of Auckland
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Definition of Food Quality• Safety
- Microbial, chemical
• Nutritional content- Micronutrients, macronutrients (composition)
• Physical and Chemical Properties- Texture, age, etc
• Appearance and sensory attributes- Freshness, ripeness, wholesomeness.
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Context
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Measurement of the quality attributes, using machine vision / image analysis:
- Non-destructive
- Near real-time
- Reliable
- Distribution as opposed to average values.
Advantage of hyperspectral
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Spectroscopy Machine vision
Hyperspectral Imaging
FastSeparates wavelengthsAverages the view area (spatial)
Spatially resolves at pixel levelAverages wavelengths
Separates at pixel levelSeparates wavelengths.
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Hyperspectral imagingWavelengths between 200 and 2500 nm.The food sample is scanned with many wavelengths.
Can measure moisture,lipids, astaxanthin,…
Methods
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2- Transmittance
Light source
Spectrometeror camera
Two difficulties:-Thickness affects penetration-Light disperses
Parasites
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Manual detection 75% effective
Imaging spectroscopy:Depth up to 0.8 cm detected
Speed:1 fillet/sec40 cm/s
Composition
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Different chemical bonds absorb at different wavelengths
It is possible to scan the food using many wavelengths, and correlate these with chemically measured composition.
Both the UV and IR range can be used.
Cocoa powder
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Near infrared reflectance factor (R) spectra were recorded for 60 cocoa powder samples
The spectra were transformed to log (R) versus and to the second derivative of log (1/R) versus wavelength for correlation with compositional data
Linear stepwise regression techniques were used to determine the optimum and other parameters for predicting chemical constituents
The ratio of second derivatives of log (1/R) measured at two characteristic wavelengths.
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Oyster Composition
Brown 2011
Oysters were homogenized
Composition was measured by wet chemistry, then scanned
high throughput: 250–300 samplescan be analyzed for moisture, fat, protein and glycogen each day.
Methods of Data Analysis
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Chemometrics:These methods include (not exclusively):
-partial least squares (PLS) regression, -multiple linear regression (MLR), and -principal component analysis (PCA).
Pork quality
Summary
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In addition to visible light analysis (size, color, shape, texture, etc) UV and IR regions can also be used for quality evaluation.
These include composition, specific objects (e.g. parasites, or bones), tenderness.
Advantages: Use of multiple wavelengths allow more insight into the materials
Disadvantages: Multiple wavelengths require complex chemometric analysis.