Q. Measurement of Colour in Foods?
A number of instruments are used for colour measurements in food.
a) A simple method is to match the colour of a food with coloured chips or glass and give them name accordingly.
b) Disc Colourimetry, in which different coloured discs are spun on a stage, so that the colours merge into one colour. The test sample is placed adjacent to the spinning disc and the colours are matched.
c) Tintometers are simple instruments used to determine the colour and its depth in foods for a more reliable measurement of colour.
d) Spectrophotometers are also used to measure colour. In the case of clear and transparent solutions, spectrophotometric measurements give quantitative results. For the foods that are opaque in nature, "reflectance spectrophotometry" is used. In the Reflectance Spectrophotometery, colour is measured in terms of amount of light reflected from the surface of the object at each wavelength in the range of 380-700 nm.
e) Tri - Stimulus Colourimetry, in which the colour is specified by three attributes - dominant wavelength, brightness and purity- hence referred to as tristimulus system. These three refer to the actual colour, luminosity and strength of the colour respectively.
Other than the measurement of colour, analysis of colour in food is also important. You may recall reading about the three different classes of colours - natural, synthetic and natural identical, earlier. How can we analyse or check whether the colour present in food, particularly the synthetic one, is permitted or not? There are different ways of colour analysis.