Chemistry, processing and toxicology of annatto (Bixa orellana L.)

Annatto of commerce is the dried seed of Bixa orellana L., an evergreen shrub or small tree, which has been introduced widely throughout the tropics. The orange red colour extracted from annatto seeds is mainly used as a food colour. Its chief application is in colouring butter and cheese. Annatto colour is also used world wide in foods like soft drinks, sugar confectionery, margarine, ice cream, fish products, etc. The orange red colour due to the carotenoids constitutes more than 80 per cent in the annatto seed coat, consists of cis-bixin [methyl hydrogen (9'Z)-6,6'-apocarotene-6, 6'-dioate], which on heating in solution converts to a more stable trans isomer and a yellow degradation product. Various constituents isolated and identified from B.orellana seeds are described. Minor carotenoids and compounds from lipid portion isolated and identified are also discussed. Extraction of colouring matter from the seed coat of annatto by several methods have been surveyed. Commercial preparations consist of solution or suspension of the pigment in vegetable oil or in water-soluble form in dilute alkaline solution. The toxicological studies and their assessment by FAO/WHO have also been reviewed. National and international standards and legislations on annatto colour are presented.