Influence of pH and Heating of Ovalbumin on Interfacial Properties and Rheology of Optimized Volume Fraction Soybean Oil-Water Emulsion Gels

The present study focuses on understanding the influence of change in pH and heating of ovalbumin (OVA) on the stabilization of soybean oil (SBO) in water emulsion gels with volume fraction (ϕ) = 0.60-0.74. OVA at acidic pH (2.6) leads to the maximum reduction of interfacial tension of the SBO-water interface, compared to that of OVA at the isoelectric point and alkaline pH (8.5). Heating of the OVA at 80-85 °C for 6 and 12 h, along with a change in pH, further decreases the interfacial tension, indicating an increase in surface activity to the OVA upon heating. The surface dilatational measurements indicate the maximum dilatational modulus for the SBO-water interface in the presence of OVA at pH = 2.6 heated for 12 h and minimum for OVA at pH = 8.5. Circular dichroism and Fourier transform infrared spectroscopy indicate the increase in the β-sheet content of the OVA upon heating. The maximum elastic modulus and yield stress are observed for emulsion gels with SBO ϕ = 0.68 with an OVA at pH = 2.6 and heated for 12 h.