Preparation of soy protein isolate using calcium chloride extraction ('s703 cip')

Abstract

A soy protein product having a protein content of at least about 60 wt % (N×6.25) d.b., preferably an isolate having a protein content of at least about 90 wt % (N×6.25) d.b., is formed by a procedure in which soy protein is extracted from a soy source material using an aqueous calcium chloride solution at low pH, generally about 1.5 to about 5, and separating the resulting aqueous soy protein solution from residual soy protein source. The resulting clarified aqueous soy protein solution may be diluted and the pH adjusted within the range of 1.5-5.0. The solution may be concentrated by ultrafiltration, diafiltered and then dried to provide the soy protein product. Alternatively, the concentrated and optionally diafiltered soy protein solution may be optionally adjusted in pH within the range of 1.5-7.0 then diluted into water to cause the formation of a precipitate, separating the precipitate from the diluting water (supernatant) and drying the separated soy protein to form a soy protein product having a protein content of at least about 60 wt % (N×6.25) d.b., preferably a soy protein isolate having a protein content of at least about 90 wt % (N×6.25) d.b. The supernatant may be processed to form soy protein products having a protein content of at least about 60 wt % (N×6.25) d.b., preferably a soy protein isolate having a protein content of at least 90 wt % (N×6.25) d.b. Alternatively, the precipitate from the dilution step may be re-solubilized in the diluting water by adjustment of the pH to resolubilize the precipitate and form a protein solution. The soy protein solution may be concentrated while maintaining the ionic strength substantially constant by using a selective membrane technique followed by optional diafiltration and drying. The soy protein product is soluble in acidic medium and produces transparent, heat stable solutions and hence may be used for protein fortification of soft drinks and sports drinks.