Q. Qualitative and Quantitative Analysis of Colour?

Primarily, two types of analysis are carried out for food colours - qualitative and quantitative.

The qualitative analysis is carried out to check whether the dye present in food as a colorant is permitted or not. This is done with the help of various separation techniques Gas Liquid Chromatography (GLC), Thin Layer Chromatography (TLC), paper Chromatography and spectrophotometry.

The colour from the food product is extracted and subjected to one of these techniques for identification of colour. In case of paper chromatography and TLC, reference values of the extracted colours are compared with that of standard and in case of GLC, retention time values are compared. Retention time is the time taken by the component to elute from the column. atography (GLC), Thin Layer Chromatography (TLC), paper chromatography and spectrophotometry.

Quantitative analysis, on the other hand, is done to check whether the amount present is within the prescribed limits or not. In case of GLC area of the peak obtained is directly proportional to the amount of the component present. In case of TLC the spotted portion is scrapped from the plate and dissolved in a suitable solvent filtered and the colour intensity is measured using spectrophotometer. If the artificial colours used are preset beyond the prescribed limit they might prove to be toxic to the human health. All these determinations are done for synthetic colours only. With qualitative and quantitative analysis of colours in foods, we come to an end of our study on the properties of foods.