Influence of pH on foaming and rheological properties of aerated high sugar system with egg white protein and hydroxypropylmethylcellulose

The objective of this study was to evaluate the effects of the total biopolymer (egg white protein - EW and hydroxypropylmethylcellulose – HPMC) concentration (1.4–5.6 g/100 g of sugar) and EW/HPMC ratio (2/1 to 18/1 g/g) on the apparent viscosity before whipping, foaming capacity (density and overrun) and foam rheological properties (G’, G” and δ) of sugar/EW/HPMC mixtures using a central composite rotatable design (CCRD). The conditions to obtain intermediate apparent viscosity, high foaming capacity, elastic and solid behaviour were total biopolymer concentration 5.0 g/100 g of sugar and EW/HPMC ratio 14/1 (g/g). Under these conditions, experiments were carried out to evaluate the effect of interactions between EW and HPMC at pH 3.0, 4.5 and 6.0 on the foaming and rheological properties. The greatest foaming capacity, elastic and solid behaviour, with no liquid drainage, were obtained at pH 3.0. At pH 4.5, foams possessed monodisperse bubble size distribution and viscoelastic behaviour, leading to better stability with respect to disproportionation and coalescence compared to foams at pH 3.0. At pH 6.0, foam showed the poorest foaming properties and viscous behaviour. The interactions between EW and HPMC in aerated confectionery at different pH affect foaming and rheological properties.