Impact of Dry Heating in an Alkaline Environment on the Structure and Foaming Properties of Whey Proteins

Dry heating (DH) in an alkaline environment has been proposed as a treatment that can improve some techno-functional properties of whey proteins, such as their water-holding capacity and gelling properties. Nevertheless, information concerning the impact of DH in an alkaline environment on the foaming properties of whey proteins is not available in the literature. In this context, lyophilized whey protein isolate (WPI) powders with and without added lactose were submitted to DH treatments (60 and 80 degrees C) under neutral and alkaline environments for 48 h. Even without DH, the alkaline environment induced the formation of insoluble protein aggregates stabilized by disulfide and non-disulfide covalent interactions. The amount of insoluble protein aggregates enhanced with the increase in the intensity of DH. No insoluble aggregates were observed for samples produced in a neutral environment. Furthermore, no difference in the apparent secondary structure of the proteins in the soluble fraction of neutral or alkaline equivalent samples could be evidenced. In addition, the intensity of the population of soluble protein aggregates rose by increasing the intensity of DH treatment; however, it was comparable between neutral and alkaline equivalent samples. DH in an alkaline environment at 80 degrees C for 48 h significantly enhanced the stability of the foams produced by the soluble fraction of lactose-added samples, corroborating its potential to improve useful techno-functional properties of whey proteins.