Aerated whey protein gels as new food matrices: Effect of thermal treatment over microstructure and textural properties

Abstract

Aerated gels (AG) contain both bubbles and entrapped water in their structure, thus offering ample versatility in product development. The objective of this study was to evaluate the effect of thermal treatment of whey protein isolate (WPI) dispersions over the microstructure and textural properties of AG fabricated with these dispersions. WPI dispersions (9% w/w) with NaCl (0.4% w/w) at three pH’s (6.50, 6.75 and 7.00) were prepared. Dispersions were subjected to thermal treatment at three temperatures (70, 75 and 80°C) at different times depending on the pH. After thermal treatment, dispersions were aerated by mechanical agitation at 2000rpm for 3min. Finally, aerated dispersions were cooled at 10°C for 24h to set the AG structure. AG were characterized in terms of their gas hold-up capacity, microstructure (bubble sizes) and textural properties. Thermal treatment temperature influenced the gas hold-up and mean diameter (DM) of air bubbles in the AG, both decreasing with an increase in temperature. Maximum gas hold-up was about 70% and DM were in the range of 530–700μm. The increase in apparent viscosity of thermally treated dispersions produced lower air incorporation in AG structure and smaller bubble sizes. Compression stress at break decreased with an increase in the thermal treatment temperature. Control of thermal treatment conditions for WPI dispersions allows to fabricate AG with different microstructural and textural properties which can be used as innovative food matrices for obesity control or delivery of bioactives.