Annatto

Introduction

Bixa orellana (Annatto) is a native of Central and tropical South America. The tree has been widely introduced throughout the tropics as an ornamental or for its dyestuffs and has become naturalised in many countries, including Jamaica. The name comes from the Spanish conquistador, Francisco de Orellana, who is credited with discovering the Amazon River in 1541.
The bush or small tree grows to around 2-3m in height and the branches bear capsules covered with soft spines or hairs. Although it requires tropical or sub-tropical conditions to thrive, it is easy to cultivate and the trees reach maturity in 4-5 years and continue to bear up to 20 years.

A stem from an Annatto tree and dried capsules that have opened to show the red seeds.

The town Annotto Bay, on the north coast of Jamaica, was originally known by the Arawaks as "Guayguata" and was called "Mellila" by the Spanish, the second city they established in the Island. Presumably the English renamed it based on them finding annatto trees being grown there? In 1774, the Post Master General of Jamaica, Edward Dismore, established a Post Office in the town which opened on the 1st January, 1774.
The Jamaica Railway Corporation commenced in 1845, making it one of the first in the world. Originally between Kingston and Spanish Town, the line through Annotto Bay to Port Antonio was constructed around 1896, but closed in 1980.

Annatto

It is considered that annatto extracts rank as the second most economically important natural colour in the world [1,2,3] and it is the most frequently used natural colour in the food industry in the UK, being used to colour margarine and dairy products.
The major colour component is the apocarotenoid, 9'-cis-bixin, which accounts for over 80% of the annatto pigment. It has been suggested [2] that over 2000 seeds have to be harvested to get just one gram of bixin and additionally that to produce one gallon of cheese colour, 240,000 seeds would have to be harvested!

A recent estimate of the world production figures are that a total of 14,500 metric tons of dried seed are harvested with Brazil, Peru, Ecuador and Kenya contributing the major proportion of this, with prices ranging from US $ 500 to 2,500 per metric ton.

The first isolation of bixin is credited to Boussingault [4], who in 1825 was living in Columbia and prior to his return to Paris became a Colonel in Simon Bolivars' army. The structure of bixin though, was not determined until 1961 [5] and there was some controversy surrounding this since it is unusual in being an example of a cis-carotenoid rather than trans-, common for most carotenoid structures. The first appreciation of geometric isomerism in bixin was by Paul Karrer, a former student of Alfred Werner. Karrer was awarded a Nobel Prize in Chemistry in 1937 for his research on "Carotenoids, Flavins and Vitamin A and B₂"

cis-bixin (monomethyl ester)

trans-norbixin (dicarboxylic acid)

In addition to bixin, numerous other pigments have been characterised from annatto extracts [6] including: six apocarotenoids (C30 and C32), eight diapocarotenoids (C19, C22, C24, C25) and a carotenoid derivative (C14). These are all in minor proportions. Norbixin is obtained by alkaline hydrolysis of bixin to give a water soluble di-carboxylic acid. It is thought that most extraction procedures cause changes in the structure with trans- bixin being the more thermodynamically stable and produced by heating the cis- isomer. This may explain why both cis- and trans- norbixin result from alkaline hydrolysis.

An example of an HPLC of annatto extracts is available at the Merck site under Chromolith(R) RP-18 endcapped menu and a simulation of this in JCAMP-DX format has been produced.
A chloroform extract produced the following UV/Vis spectrum. Note that it has been suggested that quartz cells should NOT be used for determining the spectrum since the sample will undergo rapid degradation in the presence of light with wavelength below 300nm.
The 1% extinction coefficients for Peaks II and III of bixin (470, 501nm) and norbixin (453, 482nm) have been reported [2] to be 3016, 2714 and 3208, 2867 respectively.
The Raman spectrum of bixin has been published [7] and shows strong bands at 1525, 1190, 1155 and 1010 cm^-1.

The various colour codes to denote annatto extracts are:
European Community Identification number: Food color E-160b
USA: 21 CFR 73.30 Food Chemicals Codex
EINECS number: 289-561-2
Orange-3, CI Natural Orange 4, Orlean
Color Index (1982) number 75120

There have been recent concerns about the use of artificial dyes in foodstuffs and a trend towards the use of "natural" dyes. Annatto extracts have generally been classified as safe and in the US treated as exempt from certification as a colour additive in food.
Annatto extact samples have been designated as "direct - alkali or oil extracts" and as "indirect - solvent extraction methods". Alkali extraction gives mainly cis-bixin and the salt of cis-norbixin. Hot oil is known to aid in the conversion of the cis-bixin to trans-norbixin which is slightly more soluble and used in oil based foods like margarine. It is of interest then that decomposition products of bixin appear to be more prevalent in commercial samples that have undergone processing with some form of heat treatment; for example, toluene levels as high as 12 ng/kg and m-xylene as high as 200 ng/kg in oil extracted seeds [8]. This might suggest that the indirect methods have an advantage in terms of quality?

Other extracts

The Phytochemical and Ethnobotanical Database reports nearly 300 chemicals identified in Bixa orellana.

Annatto extracts from leaves, roots and seeds have traditionally been used for medicinal purposes by South American Indians for the treatment of wounds and to treat diarrhea and asthma [2]. Extracts from annatto have been shown to have a hyperglycaemic principle [9].

References

[1] "Dye Plants and Dyeing", J and M Cannon and G Dalby-Quenet, Timber Press, (Jan 1 2003), ISBN 0881925721.
[2] "Natural Food Colorants", Chapter 6, edited by G.J. Lauro and F.J. Francis, Marcel Dekker, Inc, N.Y. 2000, ISBN 0-8247-0421-5
[3] "Natural Colourants and Dyestuffs", FAO Report 1995, ISBN 92-5-103747-7
[4] J.B. Boussingault, Ann. Chem., 1825, 28, 440-444.
[5] M.S. Barber, A. Hardisson, L.M. Jackman, B.C.L. Weedon, J. Chem. Soc., 1961, 1625.
[6] A.Z. Mercadante, A. Steck, H. Pfander, Phytochemistry, 52, 1999, 135-139.
[7] L.F.C. de Oliveira, S.O. Dantas, E.S. Velozo, P.S. Santos, M.C.C. Ribeiro, Journal of Molecular Structure 435, (1997), 101-107.
[8] M.J. Scotter, L.A. Wilson, G.P. Appleton, and L. Castle, J. Agric. Food Chem. 2000, 48, 484-488.
[9] E.Y. Morrison, H. Thompson, K. Pascoe, M. West and C. Fletcher, Trop. Geogr. Med., 43, 1991, 184-188.

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Created and maintained by Prof. Robert J. Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.

Created 7th November 2004. Links checked and/or last modified 8th August 2014.
URL http://wwwchem.uwimona.edu.jm/lectures/annatto.html