Stability of bixin in annatto oleoresin and dye powder during storage

Annatto dye is a natural colour extracted from the pericarp of seed of Bixa orellana L. Bixin is the principle colouring agent, and can be extracted from the annatto seeds into oil, alkali and organic solvents. Considerable losses were reported during storage in bixin content of annatto dye depending upon the conditions. In the present study, the loss of bixin in annatto dye stored in the form of dye powder or annatto oleoresin at three different conditions, viz; cold conditions in darkness, in darkness at room temperature (RT) and at RT in diffused daylight were evaluated spectrophotometrically at 470 nm in choloroform. Accordingly, annatto oleoresin and dye powder of approximately equivalent bixin strengths were exposed to different storage conditions in glass bottles for a period of 360 days. The losses were very high in the case of dye powder when compared to the oleoresin under all the storage conditions. Mass fraction of bixin lost in oleoresin stored at cold dark conditions was negligible (0.011) throughout the study, whereas considerable losses were observed in dye powder (0.229). The mass fraction of bixin lost in oleoresin and dye powder samples stored at RT (dark) were 0.082 and 0.542 respectively. Similarly in case of RT (diffused day light) conditions, the losses of bixin in oleoresin and dye powder were 0.136 and 0.600, respectively. Loss of 0.154 was observed in bixin content in the seed stored in jute bags during the period. The second-order rate constants for degradation of bixin were calculated, and were found to be much lower for oleoresin when compared to dye powder. It is recommended that the dye can be conveniently stored in the oleoresin form until it is formulated for application in foods.