Optimization of fluidized bed drying process of green peas using response surface methodology

The fluidized bed drying process of green peas was optimized using the response surface methodology for the process variables: drying air temperature (60-100 degrees C), tempering time (0-60 min), pretreatment, and mass per unit area (6.3-9.5g/cm(2)). The green peas were pretreated by pricking, hot water blanching, or chemical blanching. Product quality parameters such as rehydration ratio, color, texture, and appearance were determined and analyzed. Second-order polynomial equations, containing all the process variables, were used to model the measured process and product qualities. Rehydration ratio was influenced mostly by pretreatment followed by tempering time, temperature, and mass per unit area. Pretreatment and mass per unit area significantly affected color and texture. Higher levels of temperature and lower levels of tempering time and mass per unit area increased the rehydration ratio. The optimum process conditions were derived by using the contour plots on the rehydration ratio and sensory scores generated by the second-order polynomials. Optimum conditions of 79.4 degrees C drying air temperature, 35.8-min tempering time, pretreatment of the once pricked peas with chemical blanching in a solution of 2.5% NaCl and 0.1% NaHCO3, and mass per unit area of 6.8 g/cm(2) were recommended for the fluidized bed drying of green peas. At these conditions the rehydration ratio was 3.49.