Study of the flash drying of the residue from soymilk processing - "okara"

Abstract

The objective of this research project was to study the drying of soymilk residue in a pneumatic flash dryer, using Response Surface Methodology (RSM), and to evaluate the quality of the dried residue. Soymilk residue, also known as okara, was provided by a Brazilian soymilk factory. RSM showed that for a 120 second drying cycle, the lower the residue moisture contents (y) obtained, the higher the recirculation rates (x1 ), regardless of the air drying temperature (x2), and it could be expressed by the equation y = 7.072 - 7.92x1, with R2 = 92,92%. It is possible to obtain okara with 10% of moisture (dwb) under the condition x1 =1.25, equivalent to RR = 61%, with air drying temperatures ranging from 252 °C to 308 °C. The dried okara obtained through Central Compound Rotational Design (CCRD) presented a centesimal composition similar to the okara dried in a tray dryer, known as the original okara. There were significant variations (p ≤ 0.05) in the Emulsifying Capacity (EC), Emulsion Stability (ES) and Protein Solubility (PS) between the dehydrated residues obtained. It was concluded that the flash drying of okara is technically feasible and that the physicochemical composition of the residue was not altered; on the contrary, the process promoted a positive effect on the technological functional properties.