Preparation of soy protein isolate using calcium chloride extraction (“S703”)

A process of producing a soy protein product having a soy protein content of at least about 60 wt % (N×6.25) on a dry weight basis, which comprises:

• (a) extracting a soy protein source with an aqueous calcium salt solution at a pH of about 1.5 to about 5.5 to cause solubilization of soy protein from the soy protein source and to form an aqueous soy protein solution,
• (b) separating the aqueous soy protein solution from residual soy protein source,
• (c)following said separation step, adjusting the pH of the aqueous soy protein solution to a different value within the range of about 1.5 to about 5.0,
• (d) concentrating said soy protein solution while maintaining the ionic strength thereof substantially constant to produce a concentrated soy protein solution having a protein concentration of about 50 to about 300 g/L and the concentrated soy protein solution is optionally diafiltered, and
• (e) drying said concentrated and optionally diafiltered soy protein solution.