Study On Separating Soybean Whey By Membrane Technology

Soybean whey will be drained during producing soybean products, according statistics, 2-5 tons of soybean whey wastewater will be produced when processing 1 ton of soybean. There are some physiologic substances in soybean whey, for example soybean whey protein, soybean oligosaccharide, soybean isoflavones, saponins etc. But because the concentration of these physiologic substances in soybean whey is very low, it is difficult to realize industrialized application by using traditional methods. Along with the progress of membrane technology and membrane module, membrane separation become effective methods for separating and concentrating low concentration solution, so it will be possible to recover and utilize soybean whey. Soybean whey protein could be concentrated and separated from oligosaccharide and inorganic salts by choosing suitable ultrafiltration membrane; soybean oligosaccharide could be separated from inorganic salts by choosing suitable nanofiltration membrane.Using ultrafiltration and nanofiltration to separate soybean whey from producing tofu was studied in this paper. The selection of ultrafitration membrane, the effect of pH, pressure, temperature, concentration multiple, velocity of condensed liquor were researched; the ability of each cleaning reagent and ways was determined; using nanofiltration to concentrate soybean oligosaccharides was discussed then.The results show: Comprehensively considering flux, decline factor, protein rejection coefficient and carbohydrates permeation rate, PS-10 is the suitable membrane for separating soybean whey. When pH was varied from the isoelectric point, flux will increase, decline factor will decrease, protein rejection coefficient will not change and carbohydrate permeation rate will increase with the few, the optimum pH for PES-10 is 11, and for PS-10 is 6.2; the water flux will increase along with pressure's increasing, but the water flux will become a constant gradually when pressure exceed the critical pressure, the optimum pressure is 0.2~0.25MPa. Ultrafitrating soybean whey by hollow fiber membrane, flux will be improved by increasing velocity of condensed liquor and temperature, the concentration multiple will be 2.7 under 0.1MPa,40℃ and velocity of condensed liquor 36L/h. Comparing each cleaning reagent, SDS> EDTA+NaOH >Na5P3Oio >NaOH>HCl. Result of nanofiltration experiment show: the optimum pressure is 0.5MPa, and the optimum temperature is 40℃; when concentration multiple increasing, inorganic salts rejection coefficient will decrease and carbohydrates rejection coefficient will not change; Concentration multiple will exceed 10 by nanofiltration under 0.5MPa, 40℃.