Recovery of protein from tofu whey wastewater using protein-based coagulant

Tofu whey wastewater is the protein-rich liquid by-product of tofu production that has the potential as a source stream for biobased products. Coagulation can be used to recover protein from tofu whey. Biobased coagulants are alternatives for polymer- and metal-based coagulants, particularly if the precipitate is recovered and used for further processes. The tofu whey coagulation performance of three protein-based coagulants, namely soy protein isolate, Moringa oleifera seed, and isolate of Moringa seed protein, was determined with the jar test method. The pH (4, 5, 7, 9) and protein dosage (33-191 mg-protein/L) were varied. The results were compared with chitosan, as a benchmark for biobased coagulants, with similar pH variation and 100-800 mg-chitosan/L dosage variation. Our experiment showed that the optimum pH for protein coagulation was 4 (the initial pH of the tofu whey). Up to 95% turbidity could be removed, with chitosan shown to be the most effective coagulant. On the other hand, chitosan only removed up to 9% of organics as chemical oxygen demand (COD), while soy protein isolate could remove up to 20%. The highest protein removal was obtained by soy protein isolate (35%) followed by Moringa seed (34%), chitosan (25%), and Moringa seed protein (13%). Meanwhile, coagulation with soy protein isolate could recover 11% protein in the precipitate at 60% protein content. Higher protein removal compared to COD suggests a preference towards protein coagulation compared with other organics. Our results suggest that protein-based materials can be applied to recover proteins from tofu whey.