Relationship between the colour and the chemical structure of carotenoid pigments

Several carotenoids were isolated and their colours were ascertained objectively to establish relationships between the chemical structures of those pigments and their actual colours, considering the coordinates of the uniform space CIELAB. The results of this study revealed that the different carotenoids surveyed could be grouped in the a∗b∗ plane according to the number of conjugated double bonds. For yellowish carotenoids, it was observed that a∗ values clearly decreased from those with 11 conjugated double bonds (c.d.b.) to those with 9 c.d.b., although this trend reversed in the case of carotenoids with 7 c.d.b.. In terms of hue (hab), it was seen that the decrease in conjugation of the molecules involved a slight rise in hab. On the other hand, the aperture of the end rings or the increase in conjugation involved clear increases in hue.