Calculation of CIE Color Specifications from Reflectance or Transmittance Spectra
Food color is arguably one of the most important determinants of acceptability, and is, therefore, an important specification for many food products. The development of compact and easy-to-use colorimeters has made the quantitative measurement of color a routine part of product development and quality assurance.
There are several widely employed systems of color specification: notably Munsell, Commission Internationale de l’Eclairage (CIE) tristimulus, and the more recent CIE L*a*b* system. The Munsell system relies on matching with standard color chips. Value, hue and chroma are employed to express lightness, “color” and saturation, respectively. The CIE tristimulus system uses mathematical coordinates (X, Y and Z) to represent the amount of red, green and blue primaries required by a “standard observer” to give a color match. These coordinates can be combined to yield a two-dimensional representation (chromaticity coordinates x and y) of color. The CIE L*a*b* system employs L* (lightness), a* (red-green axis), and b* (yellow-blue axis) to provide a visually linear color specification.
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