Rotating-Pulsed Fluidized Bed Drying of Okara: Evaluation of Process Kinetic and Nutritive Properties of Dried Product

Abstract

Okara is a byproduct of soymilk processing and is rich in fiber and protein. It is underutilized in the food industry as an ingredient owing to its high perishability. The objective of this work was to study the drying of okara in a rotating-pulsed fluidized bed dryer to verify the effect of air temperature (50–90 °C) and frequency of disc rotation (7.5–24.5 Hz) on the inactivation of trypsin inhibitors and the retention of the total phenolic compounds and isoflavones. The drying process was effective in drying this cohesive material. The process conditions exhibited no significant effect on the activity of trypsin inhibitors and content of total isoflavones. However, the content of total phenolic compounds was affected by the air temperature, in which the higher retention occurred at 70 °C and 16 Hz. Regarding the conversion of isoflavone classes, the drying process favored the hydrolysis of malonylglycosides and β-glycosides into aglycones.