Colorimetry and spectrophotometry for food products
- How does it work?
- What can it be used for?
- What can it not be used for?
- Related Facilities
- Further Information
|Key words||Colorimetry, spectrophotometry, colour measurement, food, visual identification, non-invasive|
How does it work?
|Primary objective|| Colorimetry: quantify and evaluate the colour of an object.
Spectrophotometry: quantify and evaluate the transmission properties of a material as a function of the wavelength of an object.
|Working principle|| Colour is one of the important features used by consumers to assess the quality of a food product. It may be defined as the individual's response to the visual signals generated by the light on a product. Thus, it is very important how colour is perceived and measured and what are the ways in which it can be better understood and controlled in food. In current food industries’ practice, two principal colour measurement techniques are used [1-3]:
Colorimetry concerns the quantification and physical description of the human perception of colours. Colorimetry is the technique which quantifies colour by measuring three primary colour components of light which are seen by the human eye, specifically, red, green and blue (also referred to as “RGB”). These colour measurements provide data on how much of these three components are present in the light transmitted or reflected by a sample. The obtained data are mainly characteristic of the sample since light absorption is specific of each sample. The absorption of light in a certain medium is described by the Beer – Lambert law
I = I0e-x
Where I0 = incident intensity, I = emergent intensity, = absorption coefficient and x = the distance the light travels through the material. The Beer – Lambert law relates the absorption of light to the properties of the material through which the light is traveling via the parameter.
While in spectrophotometry the light is broken up in a spectrum, colorimetry uses band filters to reduce colour spectra to the physical correlates of colour perception, most often the CIE 1960 XYZ colour space tristimulus values.
The result of the spectrophotometric measurement is the absorption spectrum of the sample representing the absorbed intensity versus the wavelength, I = f(λ).
|Additional effects||Spectrophotometry is also used for instance for measuring (bio) chemical reactions (such as e.g. enzyme activity) that involve changes in the emitted spectrum.|
|Important process parameters||sample, instrument geometry used for measurement, instrument calibration|
|Important product parameters||geometry, dimension, colour, consistency, sample presentation [3-7]|
What can it be used for?
|Products||Colorimetry and spectrophotometry can be used for all type of food products (solids and liquids) since both transmission and reflection measurement techniques are available .|
|Operations||Quality control and monitoring of processes which take place during the manufacturing, packaging, shipping or storing of food products.|
|Solutions for short comings||Non-invasive method.|
What can it NOT be used for?
|Other limitations||In the case of opaque products, measurements of the reflected light intensity are available. Also in case of floating particles in a liquid sample, it’s better to filter the sample prior to measuring colour.|
|Risks or hazards||The use of colorimetry and spectrophotometry for food control presents no risks.|
|Maturity||Colorimetry and spectrophotometry are mature control techniques. Equipments are available for both laboratory and industrial use.|
|Modularity /Implementation||Colorimetric and spectrophotometric techniques can be easily inserted in an existing production line. The operation of the related equipments is simple.|
|Consumer aspects||No negative aspects expected.|
|Environmental aspects||Colorimetry and spectrophotometry are environmentally friendly techniques.|
Facilities that might be interesting for you
|Companies||Konika Minolta, HunterLab, Optronik|
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