Exergy driven process synthesis for isoflavone recovery from okara

Abstract

Isoflavones, found in soybeans and other members of the fabaceae family, are considered bioactive components of high economic value. An opportunity would be to separate isoflavones from okara, the by-product of the soymilk and tofu production. Such a process would not only valorise that side-stream but also, and maybe more importantly, reduce the waste of high quality bioactive compounds. Extraction is an important part during the recovery of isoflavones from okara and was conceptually designed in this work. Due to environmental constraints, ethanol and water were the only solvents considered in this work for extraction of isoflavones. Different process scenarios were established and assessed by solvent footprinting, energy use, and exergy analysis. Simulation of the various process scenarios showed that distillation and the loss of ethanol in the spent okara represent the largest inefficiencies regarding exergy waste and energy usage. Furthermore, even though the use of ethanol leads to a higher recovery, water is in most cases the preferred solvent due to the high exergetic cost of losing some ethanol in the spent okara and during distillation.