Production of soy protein concentrates using a combination of electroacidification and ultrafiltration

Soy protein concentrates produced by combining electroacidification and dead-end ultrafiltration with a membrane of 100 kDa (pH 7 and 6) were compared with concentrates produced by ultrafiltration (pH 9) and a traditional acid precipitation procedure at pH 4.5. Mineral removal during ultrafiltration (mainly potassium, phosphorus, and calcium) was enhanced for the pH 6 electroacidified extract, compared to the extract at pH 9. This yielded a concentrate with improved solubility characteristics. The solubility for the concentrate prepared at pH 6 was enhanced by as high as 45% when compared to the concentrate at pH 9. The concentrate produced according to the traditional acid precipitation process showed mineral contents and solubility profile similar to those of the pH 6 concentrate, but required twice as much water during the process. The effect of electroacidification treatments on ultrafiltration permeate flux was quantified through the measurement of the different hydraulic resistances. Cake resistance was the main resistance to the permeate flux, and it was minimum at pH 9, maximum at pH 7, and intermediate at pH 6.