Calcium carbonate-hydrolyzed soy protein complexation in the presence of citric acid

The influence of hydrolyzed soy proteins on calcium carbonate stabilization was studied in citric acid solution. Calcium-soy proteins interactions were characterized using a calcium ion selective electrode, turbidity, and Isothermal Titration Calorimetry. Once the meta-stable phase was reached or just after soy protein addition, spray-drying was performed and SEM, XRD, and XPS analysis were carried out on spray-dried powders. In citric acid solution calcite crystals were eroded giving rise to smaller amorphous particles. In the presence of soy proteins, complexation exothermic in nature occurred with the mineral phase, which prevented CaCO3 from recrystallisation and kept the system in an amorphous state. SEM performed on spray-dried powder showed that soy proteins were swollen in presence of mineral phase and resulted in a decrease of calcium concentration at the extreme surface of the studied powders as demonstrated by XPS. (C) 2010 Elsevier Inc. All rights reserved.