Carotenoids as food colourants.

INTRODUCTION Carotenoids are one of the most important groups of natural pigments. It has been estimated that nature produces about 100 million tons of these pigments per year. They give brilliant yellow and red colours to many fruits, vegetables, roots, flowers and autumn leaves; they produce the colour of the egg yolk, of many algae, yeasts and mushrooms, Crustaceae as well as of the feathers and skins of many birds. The carotenoids have attracted the curiosity of scientists since the beginning of organic chemistry, actually since 1818. Numerous outstanding chemists made valuable contributions and many tools and methods have been introduced into organic chemistry via the carotenoids'. I mention the early analyses (by Willstätter and Zechmeister), the rediscovery of column chromatography by Kuhn and Karrer and of the thin-layer chromatography by Stahl2, the elucidation of the isoprene rule by Ruzicka and of the symmetrical structures of squalene, /3-carotene and lycopene by Karrer, the studies on comparative biochemistry by Goodwin3, the first rules on u.v.absorption of polyenes by Richard Kuhn, the investigation of cis—trans isomerism (Pauling and Zechmeister4) and the first syntheses by Karrer and Inhoffen. The application of n.m.r. spectroscopy by Jackman and Weedon5 proved to be a valuable tool for the identification of carotenoids, the synthesis of which was especially advanced by the development of condensation reactions for the buildup of the conjugated chain (Wittig6, Homer7). We aimed at the development of commercial syntheses of some selected carotenoids arid the investigation of their use as food colourants. By substituting natural colouring matters for artificial dyes we fulfil a physiological desideratum that good food should not contain unnatural pigments.