The seeds of the shrubby Achiote or Annatto tree (Bixa orellana) are the source of annatto dye, which contains the soluble reddish-orange carotenoid pigment known as bixin, one of the most widely used natural colorants in the world (second only to saffron in economic importance). Annatto has major uses in the food and cosmetics industries and annual world consumption exceeds 10,000 metric tons. There are a range of varieties of Achiote that differ in traits including not only the shape and color of flowers and seed capsules, but also pigment concentration. The market price of annatto is proportional to its bixin content. (Nisha et al. 2012; Akshatha et al. 2011)
Annatto, which is the only member of the plant family Bixaceae, is cultivated widely in the tropics. It was widely distributed and cultivated in the New World tropics long before being spread around the globe (Leal and Michelangeli de Clavijo 2010). The leaves of the plant are ovate with a round, heart-shaped base and a pointed tip. The petioles (leaf stalks) are swollen at both the base and apex. The flowers may be white, pink, or purple. The fruit capsules are bi-valved (i.e. with two halves that fit together) and covered with soft bristles. Upon ripening, they split open to reveal numerous reddish-orange seeds. Annatto is produced mainly in the aril portion of the seed. Bixin is an apocarotenoid and constitutes up to 82% (w/w) of the total pigment present. Akshatha et al. (2011) found that plants bearing pink flowers and red ovate fruit-bearing varieties were superior in their growth, number of fruits per bunch, seed number per fruit, and annatto pigment content. (Akshatha et al. 2011 and references therein)
Aspects of the cultivation of Achiote and the downstream processing of annatto pigment have been reviewed by Aparnathi et al. (1990) and Satyanarayana et al. (2003), respectively.
There has been much interest in analyzing the biochemical pathways used by Achiote to synthesize bixin, as well as in understanding the genetic and biochemical bases for differences among varieties. These investigations may lead to the development of more efficient and more predictable methods of bixin production through genetic engineering and/or tissue or cell culture (e.g., Bouvier et al. 2003; Rodríguez-Ávila et al. 2011; Mahendranath et al. 2011)