Whey protein isolate (WPI) dispersions (15, 20 and 25%, w/v) were prepared. After whipping, erythritol was added to obtain WPI/erythritol ratios of 1:0, 1:1 and 1:2. Surface tension of the pre-foam solutions, foam overrun and their rheological properties were determined. Foam stability was evaluated in a Turbiscan. Liquid foams were solidified at 130 °C for 2 h. For solid foams, texture, surface (roughness and spreading kinetics) and microstructural properties were determined. Protein/erythritol at a ratio of 1:2 was detrimental for overrun and rheological properties of liquid foams; however, it improved their stability. Higher concentrations of erythritol produced a smoothing effect on meringue surfaces. At higher protein and erythritol concentrations, hardness and fracturability increased. The samples without erythritol demonstrated the greatest kinetics of spreading. The 1:1 protein/erythritol ratio was the most effective in maintaining an aerated structure; however, the ratio 1:2 resulted in an increase of final meringue volume.