Reflectance colour measurement instruments

Mathematical approaches that make use of concepts associated with colour space for colour measurement and specification based on reflectance spectroscopy have become well-established. Indeed the calculations involved are normally implemented in the software that is provided within an instrument used for colour measurement. The basis of all colour measurement systems is the CIE system of colour specification, which was agreed in 1931. The Commission Internationale de I Eclairage (CIE) is an international organisation promoting cooperation and information exchange on matters relating to the science and art of lighting. An important approach used for the... 

There are a variety of instruments available for the measurement of colour. Colorimeters usually determine the proportions of the primary additive lights which are necessary to match the colour reflected or transmitted by the sample under investigation. Spectrophotometers differ in that they record the intensity of the reflected light continuously over the whole spectral range. 

There are a bewildering variety of methods and instruments available to the food technologist in the field of colorrr measurement. When one is approaching the subject for the first time or when attempting to devise a method for a material outside the normal experience, the wealth of possibilities available sometimes makes the choice difficrrlt. It is the purpose of this chapter to attempt to identify a systematic approach in order to ease the task. The approach is concerned primarily with the use of tristimulus colorimetry and reflectance spectrophotometry. These two techniques will be discussed in detail along with colour scales and formulae commonly in use. The key points which may influence measured results will also be described followed by advice on the selection, preparation and presentation of samples. Finally, detailed references to work carried out in the field of food colour measirrement and where to access further information will be provided. 

A technique for the quantitation of coloured bands or spots on chromatograms or electrophoretic strips. Colour intensity can be measured by transmission, when light is allowed to pass through the sample, or by reflectance, when light is reflected from the coloured area. TTie coloured areas are represented as peaks on a chart recorder, and, from this, the area under each peak can be determined. In some instruments, the area under each peak is automatically integrated. Albumin in some laboratories is measured by densitometric techniques. Densitometers can also be used in the measurement of amniotic fluid lecithin sphingomyelin ratios. 

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