Foams Stabilized by β-Lactoglobulin Amyloid Fibrils: Effect of pH

beta-Lactoglobulin fibrils could serve as a surface-active component and form adsorption layers at the air/water interface. In this study, the physical parameters related to the surface adsorption, foaming, and surface properties of beta-lactoglobulin fibrils as a function of pH (2-8) were investigated. Results showed that an increase of pH from 2 to 5 led to a rise of the viscoelastic modulus of the surface ladsorption layer and half-life time (t(1/2)) of foams, but it decreased foamability. When the pH was close to its isoelectric point (5-2), fibrils had the lowest electrostatic repulsion and entangled at the air/water interface resulting in a tightly packaged adsorption layer around bubbles to prevent coalescence and coarsening. When the pH (7-8) was higher than the pI of fibrils, the negatively charged beta-lactoglobulin fibrils possessed good foamability (,similar to 80%) and high foam stability (t(1/2) approximate to 8 h) simultaneously even at low concentration (1 mg/mL). It demonstrated that beta-lactoglobulin fibrils with negative charges presented a good foaming behavior and could be a potential new foaming agent in the food industry.