Thermal Versus High Hydrostatic Pressure Treatments on Calcium-added Soybean Proteins. Protein Solubility, Colloidal Stability and Cold-set Gelation

The effects of thermal treatment (TT) and high hydrostatic pressure treatment (HHPT) on calcium-added soybean protein 1% (w/w) aqueous dispersions at pH7.0 were compared. High hydrostatic pressure, but not thermal treatment, improved protein solubility and colloidal stability. Despite the fact that the glycinin solubility is more affected by calcium than that of -conglycinin, glycinin could remain in dispersion in the presence of calcium when denatured by HHPT (calcium added before or after treatment), but not when denatured by TT or without denaturing treatment. Thus, polypeptide composition of soluble aggregates depended on type of treatment. Colloidal stability and molecular weight of soluble aggregates depended on the order of application of calcium and denaturing treatment: when calcium was present during either HHPT or TT, the dispersions had higher stability and higher proportion of soluble aggregates with high molecular weight than when calcium was added after treatments. After freeze drying and re-dispersing at higher protein content (10% w/w) calcium-added dispersions subjected to HHPT formed cold-set gels that were transparent and exhibited excellent water holding capacity. Our results provide the basis for the development of ready-to-use functional ingredients.