CONICET | Buscador de Institutos y Recursos Humanos

The enrichment of a diet with non-conventional proteins with high biological value and micronutrients such as iron, calcium and magnesium represents an issue of current interest. Generally the divalent ions of these minerals form insoluble species with soybean proteins damaging their important functional properties, limiting their use in certain kinds of food like liquid stuffs. High hydrostatic pressure (HHP) is an emerging technology able to inactivate microorganisms and enzymes that also may modify macromolecular structure. The aim of this work was to study the effect of HHP on soybean protein-ions interaction and their precipitation, in order to incorporate soybean proteins, supplemented with minerals, as food ingredients. Soybean protein isolate (SPI) was prepared by isoelectric precipitation. Dispersions of SPI were prepared at 10 g/L in distilled water. CaCl2, FeSO4 or MgCl2 were added in various concentrations between 1.5 and 7.5 mmol / L and pH was adjusted between 5.9 and 8.0. Protein dispersions were subjected to HHP at 600 ± 5 MPa during 5 minutes at room temperature. After HHP treatment protein solubility and stability of dispersions were determined. Our results showed that HHP treatment improves the solubility of SPI dispersions enriched with minerals (59.1 % for calcium at 5 mmol / L; 37.2 % for magnesium at 5 mmol / L and 15.2 % for iron at 3 mmol / L). The solubilizing effect of HHP was greater for calcium than for magnesium and iron, and was greater at the highest assayed pHs (7.5 % vs. 42.4 % for calcium at 7.5 mmol/L between 7.0 and 8.0 respectively), and at the lowest evaluated ion concentrations (85.3 % for calcium at 2.5 mmol/L). The velocity of sedimentation of insoluble proteins in calcium-enriched SPI decreased markedly after HHP treatment. These findings suggest that HHP might be useful to formulate soybean based beverages enriched with minerals improving their solubility and stability.