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74 FOOD & DRINK TECHNOLOGY


sucrose in biscuits; n Measurement of components


in powders, for example to detect particles of added dried gluten in


wheat flour; n Detection of damage in fruit; n Measurement of fish and beef quality.


Samples are presented on a moving translation stage and imaged with a SWIR spectral camera (Specim Ltd.) using a pushbroom approach. A HgCdTe detector provides a wavelength range of 970 to 2500nm and a selection of lenses provide a field of view of 10 to 300mm with a minimum pixel size of 30µm.


Fig. 3. The scanning electron microscopy gives pseudo-three dimensional images with higher magnification and greater depth of focus than a light microscope.


their ‘elemental fingerprint’). It can also rapidly identify samples erroneously reported as glass such as struvite (magnesium ammonium phosphate), salt and silica minerals.


Colour


Colour is a familiar basis for recognising different components, for example to discriminate lean regions from fat in meat for assessment of marbling. Chromameters and spectrophotometers are widely used in the food industry for accurate measurement of average colour over an area of a sample. A common measurement scale is the CIELAB system, which provides a standardised description of colour by three parameters L*, a* and b*:


L* Lightness (0-100) a* Variation from green (-100) to red (+100) b* Variation from blue (-100) to yellow (+100)


Methods are available to calibrate colour imaging devices against such scales, enabling accurate colour measurements to be made for individual regions. Approaches include


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hyperspectral imaging using spectral cameras or a series of narrow-band illumination sources (eg, Videometer), or calibration of a digital camera.


At Campden BRI, we use a DigiEye imaging system (Verivide Ltd) for this purpose. Te system includes an imaging cabinet with standardised lighting. Images are taken with a high resolution digital camera and the system is calibrated against a reference colour chart. Te system can be used for colour measurement, and provides accurate images for documentation of process trials and production of specification images.


Hyperspectral NIR We use a hyperspectral near infra- red imaging system to measure distributions of composition in a range of food samples. Applications have included:


n Moisture distribution in bread, biscuits and multi- component products such as


custard tarts. n Fat distribution in fried chips


and doughnuts; n Detection of crystalline


Fig. 4. Analytical techniques are complemented by a wide range of sophisticated imaging technologies for assessing food products..


Te method is rapid, requiring a few seconds to scan a sample. Te system at Campden BRI is designed for laboratory and at-line use. Te same approach can also be adapted for on-line measurement of samples on moving production lines.


Tim Hutton is Communications Manager with Campden BRI, Chipping Campden, Gloucestershire, UK.


www.campdenbri.co.uk


“Techniques that were once the preserve of forensics labs – like DNA profiling methods and mass spectrometry – are now equally well established in food and drink laboratories.”


Tim Hutton, Campden BRI


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