Precise Color Communication by Determination of the Color of Vegetable Oils and Fats in the CIELAB 1976 (L*a*b*) Color Space

Abstract

AbstractThe precise determination of the colour of oils and fats is a common and important parameter for the production of oils, fats, margarine, and mayonnaise. A new method has been developed and tested in order to improve reliability and reproducibility of the results. It is based on colour values, which describe the colour in a 3D space as defined by the International Commission on Illumination (CIE) as CIE 1976 (L*a*b*). The precision data obtained from a collaborative method validation test show significant improved repeatability with relative coefficients of variation of repeatability between 0.1 and 1.7% except for a very dark pumpkin seed oil (2.7%). The coefficients of variation of reproducibility range from 0.7 to 13.9 %. The signals of very intense colored samples might exceed the linear range of some measuring instruments. Solutions of colour standards tartrazine and Ponceau 4R as pure (>99 %) and non‐toxic substances are tested for laboratory calibration covering a colour space from CIE 1976 L* (63–99), a* (−23–67), and b* (0.5–119). A storage experiment with these standard substances is carried out and the results show improved stability over a period of 80 days compared to bromothymol blue and iodine standard solutions.Practical Applications: The results of this study show the suitability of an analysis method for the determination of the colour of oils and fats using the 3D CIE 1976 colour space as an alternative to the common Lovibond system of red and yellow colour values. As the international harmonized approach of the CIE 1976 colour space is widely accepted for the communication of precise colour description and differences between two different colors in many applications all over the world, this will be also an advantage for the communication and specification of colors in the oils and fats industry, market, and trade. In addition, the use of easy to prepare colour standard solutions enables every laboratory to check the suitability of their colour measuring device in a convenient way.