Combined effect of dynamic heat treatment and ionic strength on the properties of whey protein foams – Part II

The aim was to investigate the effect of dynamic thermal treatment in a tubular heat exchanger on the denaturation and foaming properties of whey proteins, such as overrun, foam stability and texture. A 2% w/v WPI solution (pH 7.0), with and without NaCl addition (100 mM), was submitted to heat treatment at 100 °C. The results demonstrated that heat treatment slightly reduced overrun, whereas NaCl and heat treatment improved foam stability, enhanced texture and provided smaller bubble diameters with more homogeneous bubble size distributions in foams. The foaming properties of proteins, especially stability, were shown to depend not only on the amount of protein aggregates, but also on their size. While insoluble aggregates (larger than 1 μm diameter) accelerated drainage, soluble aggregates (about 200 nm diameter) played a key role on the stabilization of gas–liquid interfaces.