Morphological diversity in Bixa orellana L. and variations in annatto pigment yield

The aim of this research was to study morphological variation in Bixa orellana which produces the pigment, annatto, in the aril portion of its seeds. Annatto dye is an important natural food colourant. B. orellana plants produce three different flower hues (e.g., pink, purple, and white) which, upon anthesis, develop into red, greenish-red, or green-coloured fruit, respectively. Measurements of fruit characteristics, together with their pigment profile data, were used to identify the superior variety with respect to its pigment yield in the field. Ovate red, conical greenish-red, and hemispherical green fruiting varieties were observed. Among those with conical fruit, significant morphological variations were observed and these could be segregated into seven types. In addition, there were differences in seed weight among the three different fruiting varieties. Ovate red-coloured fruit were found to be superior in all morphological characteristics, with an average length and width of 5.04 +/- 0.11 cm and 3.34 +/- 0.15 cm, respectively. Seed number was highest with an average of 46 seeds, in ovate red-coloured fruit which also produced the highest seed yields (1.5 - 2.0 kg of seeds per plant) with <= 2.13% (w/w) total annatto pigment content.