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

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.

Industrial relevance

Calcium enriched plant proteins with good techno-functional properties is a prevailing need, considering the current cultural, economic and environmental changes that occur. The findings of this study could serve as an input for the incorporation of high biological value proteins and calcium into aerated foods, and would contribute to develop innovative products. Treatment with high hydrostatic pressure could be advantageous on account of modifying the protein structure and thereby improving the stability of the foams. Under certain conditions, such as those of aerosol whipping creams, high hydrostatic pressure would simultaneously improve techno-functional properties of proteins and pasteurize the dispersions, which would then have to be safely canned.