Soy whey: More than just wastewater from tofu and soy protein isolate industry

Background: Soy whey is a by-product generated from both tofu and soy protein isolate production. This by-product contains a substantial amount of nutrients consisting of proteins, simple sugars, oligosaccharides, minerals, and soy isoflavones. Soy whey is commonly disposed of into the sewage after it is generated, and this pollutes water bodies. Scope and approach: Researchers from various countries have explored the valorization of soy whey for value-add or value creation in addition to mitigate the environmental pollution. This review article aims to evaluate the current status of soy whey valorization research and the learning points that can be adapted from the dairy whey valorization research which are more extensively studied than soy whey valorization research. Various methods of soy whey utilization are discussed, which can be broadly classified into two categories: physical and microbiological/enzymatic. Physical methods include the recovery of the nutrients (eg. isoflavone, protein and minerals) and the production of various functional ingredients (eg. emulsifiers), whereas microbiological/enzymatic methods include the production of functional ingredients using microorganisms and enzymes (eg. prebiotic and citric acid), propagation of microorganisms (eg. probiotics) as well as biofuel production. Key findings and conclusions: Even though there have been various efforts in valorizing soy whey, most of these studies still generate a significant amount of waste at the end of the processes. Therefore, there is a need to find an efficient method to significantly valorize soy whey without significant residual waste or generation of new waste and dairy whey valorization technologies may serve as a template for efficient soy whey valorization.