Improving foam stability: Calcium addition, high hydrostatic pressure, and their combinations on soybean protein isolates

Abstract

Various combinations of high hydrostatic pressure treatment (HHPT, 0.1 or 600 MPa), calcium addition (0, 0.50, or 0.75 mmol CaCl2/g protein), and protein content ([Prot.], 1, 5, or 10 g/L) were applied to soybean protein isolate (SPI) dispersions to analyze their effects on the formation and stability of foams. The significant interactions between these factors led to several combinations that improved foam stability via different mechanisms that involved different solubilities, aggregate sizes, and molecular structures of proteins. Thirty min after foam formation, calcium combined with HHPT improved volume of foam (VF30) and volume of liquid retained (VLr30), by the formation of strong interfacial films owing to the increased cross-linking ability of soluble and intermediate-sized aggregates. Calcium without HHPT had a greater effect on VLr30 than on VF30, which could be owing to the insoluble and large aggregates that blocked Plateau borders. HHPT without calcium led to small denatured aggregates that were soluble and improved the VLr30 when [Prot.] was lower.