Extraction of bixin from annatto seeds using supercritical carbon dioxide

Abstract

The solubility of 93% pure bixin in supercritical carbon dioxide (SC-CO2) and of the bixin present in annatto seeds (Bixa orellana L.) was measured. For the seeds, the measurements were made in a temperature range from 30 to 50ºC and pressure between 10 and 35 MPa and for the pure bixin, at 40ºC from 10 to 35 MPa. The main pigments of annatto seeds are bixin and norbixin, but the extracts only showed the presence of cis and trans-bixin, indicating that norbixin is not soluble in SC-CO2. The annatto seeds used in the experiments contained about 2.7% bixin and 3.1% oil. In the seeds, the crossover point of solubility was at about 28 MPa and values for solubility were about ten times higher than those of the pure bixin, giving evidence that the oil acted as a co-solvent with the CO2.