Relationships between different hydration properties of commercial and laboratory soybean isolates

Functional properties related to water protein interactions of soy protein isolates depend on the structural and aggregation characteristics of their major components (storage globulins 7S and 11S) that could be modified by t he preparation procedure, thermal and/or chemical treatments, and drying me thods. Commercial and laboratory isolates with different functionalities re sulting from their structural modifications were compared. Isolates with hi gh solubility or excessive thermally induced insolubilization or compact ca lcium-induced aggregates caused low water-imbibing capacity (WIC) values. T he highest WIC results from the balance between intermediate solubility and the formation of aggregates with good hydration properties. The apparent v iscosity of dispersions of commercial (spray dried) and laboratory (lyophil ized) isolates depends on the WIC, the morphology and size of the particles , and the interaction of the hydrated particles. The hydration properties a nd viscosity of protein isolate suspensions were strongly determined by the amount and properties of the insoluble fraction.