Beneficial Utilization Of Tofu Wastewater

Concerning tofu wastewater as raw material, the research discussed isolation of whey soy proteins from tofu wastewater by the method of ultrafiltration and flocculation and desalination and decoloring of tofu wastewater as following step. The possibility of recovery of isoflavovens by solvent extraction was also discussed in the paper, which was to utilization of tofu wastewate scientifically and reasonably.Firstly, the components of tofu wastewater were determined. The total sugar, proteins and isoflavones accounted for 47.18 %, 18.10 % and 0.38 % respectively. The separation of whey soy proteins and oligosaccharides was achieved by ultrafiltration, under the suitable conditions of using 10000 molecular weight cut-off membrane, operational pressure of 0.2 Mpa and ambient temperature, about 84.20 % of macromolecule proteins were removed, and about 97.98 % of oligosaccharides were retained. Chitosan-Alginate complexes were used as coagulating agents for treating tofu wastewater. Chitosan-alginate complexes (monomeric mixing ratio of 1.67) at 0.8 mg/mL, under the conditions of pH 4.5 exhibited optimum coagulation effects with turbidity reduction of 97.8 %, protein removal rate of 76.84 %, whereas hardly had any significantly effects on the oligosaccharide. The polymerization of proteins of tofu wastewater at different conditions by transglutaminase was studied using SDS-PAGE. It indicated that the optimum reaction conditions were as following, when the tofu wastewater kept constant(500 mL) and with addition of 3‰enzyme amount of TGase-Ⅰ, proteins were polymerized after 5 h completely.Tofu wastewater after deproteinization was treated by decoloring with active carbon. The results of single factor experiments and orthogonal experiments indicated that the optimum decoloring conditions were as follows, active carbon dosage 1.5 %, pH5.0, temperature 60℃, time 40 min, under this condition, the rate of decoloration attained to 87.39 %. The following experiment was concerning 001×7 strong acidic cation-exchange resin and 201×7 strong basic anion-exchange resin to purify the crude soybean oligosaccharides. The total volumn of resin was 1.2 times that of sugar solution, and the rate of flow was 10 mL/min. On the condition above, the effective result of desalination was gained. After all the experiments of isolation and purification, the oligosaccharides solution has a high degree of clarity, with the content of total sugar 6.41 mg/mL, sucrose 3.26 mg/mL, stachyose 2.01 mg/mL, raffinose 1.00 mg/mL. The optimum conditions of solvent extraction of isoflavovens from tofu wastewater after deproteinization were as following, the volumn ratio of ethylactate and tofu wastewater 1:2,two times extraction, extration time 30 min. The content of isoflavones from extration solvent was 46.5 ug/mL, and the ratio of extration was 51.60 %.