Bixin is the most used carotenoid in the food industry. It has been conventionally extracted from annatto seeds (Bixa orellana L.) using alkaline solutions or organic solvents. These methods, in addition to require a subsequent unit operation of bixin separation, can generate toxic waste. Thus, the demand for more environmentally attractive solutions leads to the study of alternative extraction technologies, such as mechanical extraction. This study aimed to investigate the mechanical extraction of bixin from annatto seeds using a screen-topped spouted bed unit. An experimental study was performed to verify the influence of process variables - such as mass of seeds, height of the screen inside the equipment, and air flow rate - on product yield and purity. Regression techniques were used to quantify the effects of these variables. The optimum conditions for the mechanical extraction were determined using a differential evolution algorithm. From the experimental work, it was extracted an annatto powder with variable contents of bixin, but always commercially attractive (over 30% of bixin). Using the optimization process, the conditions that led to the best extraction efficiency (for powder and bixin) and greater purity powder (above 65%) were identified. The experimental values closely agreed with the predicted values. (C) 2015 Elsevier B.V. All rights reserved.