Physicochemical Properties Improvement of Soy Protein Using Divalent Ions During a Two-Step Fractionation Process

This study proposed a two-step fractionation (TSF) method with the addition of divalent ions to produce a soy protein with lower contents of lipophilic proteins and polar lipids (less-LP SPI). Flavor volatiles profiles and some functional properties of less-LP SPI were compared with soy protein prepared from conventional acid precipitated methods (APP). Protein composition and thermal behavior analysis indicated that less-LP SPI prepared with the addition of 10 mM Ca²⁺ during TSF process contained less lipophilic proteins and less denatured proteins. Gas chromatography–mass spectrometry analysis showed that the flavor volatiles content of less-LP SPI was significantly lower than that of APP (p < 0.05). The emulsifying stability of less-LP SPI was improved in comparison to that of APP (p < 0.05), as indicated by a less significant change in the creaming index and particle size (after 14 and 30 days of storage) of the emulsion prepared with the former than with the latter. Less-LP SPI had a similar or slightly lower water solubility compared to APP, but it possessed a higher protein content and a lower lipid level. These improvements in the properties of less-LP SPI might be due to the removal of lipophilic proteins and polar lipids by the divalent ions during the TSF process.