In U.S. patent application Ser. No. 12/603,087 filed Oct. 21, 2009 (US Patent Publication No. 2010-0098818) and Ser. No. 12/923,897 filed Oct. 13, 2010 (US Patent Publication No. 2011-0038993), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described the preparation of a soy protein product, preferably a soy protein isolate, which is completely soluble and is capable of providing transparent and heat-stable solutions at low pH values. This protein product may be used for protein fortification of, in particular, soft drinks and sport drinks, as well as other acidic aqueous systems, without precipitation of protein. The soy protein product is produced by extracting a soy protein source with aqueous calcium chloride solution at natural pH, optionally diluting the resulting aqueous soy protein solution, adjusting the pH of the aqueous soy protein solution to a pH of about 1.5 to about 4.4, preferably about 2.0 to about 4.0, to produce an acidified clear soy protein solution, which may be optionally concentrated and diafiltered prior to drying.