Performance comparison between gradient orifice and uniform orifice distributors in rotating fluidization for coated jasmine rice

Abstract

A rotating fluidized bed coater offers an alternative technology in which particles are fluidized by balancing centrifugal, buoyant, and gravitational forces, thereby improving coating homogeneity and mass transfer. The coating performance between the gradient orifice distributor (GOD) and the uniform orifice distributor (UOD) was compared at rotational speeds of 20, 70, or 120 rpm. The experiment was set up to coat a turmeric-extract solution onto the surface of jasmine rice. The coating substance was sprayed from the nozzle at 35 or 40 mL/min at an air-atomization pressure of 1.5 bar for 6 or 8 min. Hot air (55 or 60 °C) flows were passed at an inlet velocity of 2.9 m/s, with 85 % by volume of the air recycled. The quality of the sample was evaluated based on its final moisture content, percentage of fissure kernels, head-coated rice yield, color, coating efficiency, total phenolic content, and antioxidant activity. Based on the results, GOD was a suitable distributor plate for producing turmeric-extract-coated rice. For optimal coating conditions, the jasmine rice should be coated at a drying temperature of 55 °C, using a coating solution spray rate of 35 mL/min, a rotational speed of 70 rpm, a spraying coating time of 6 min, and a drying time of 10 s after the spraying stage. Using these conditions, the coating efficiency was 84.2 % and the antioxidant activity of the coated rice was 30.53 % higher than that of the referent white rice.