Optimisation of ultrasound-assisted extraction of natural pigment from annatto seeds by response surface methodology (RSM)

The present study reports on the extraction of natural pigment from annatto seeds. Response surface methodology (RSM) was used to investigate the effect of process variables on the ultrasound-assisted extraction (UAE). Four independent variables including temperature (20-80 °C), sonication time (2-10 min), duty cycle (0.2-0.8 s) and the ratio of seeds to the solvent (5-20%) were studied. According to the results, the optimal UAE condition was obtained with a temperature of 72.7 °C, extraction time of 7.25 min, the ratio of seed to solvent of 14% and duty cycle of 0.8 s. At these conditions, extraction yield determined as 6.35% and the absorbance value as 0.865%. The experimental values under optimal condition were in good consistent with the predicted values, which suggested UAE is more efficient process as compared to conventional extraction.