Enhancement of emulsifying properties of whey proteins by controlling spray-drying parameters

Whey protein concentrate is the main source of globular proteins in food products which are principally used as emulsifying, foaming and gelling ingredients. These whey proteins are commonly used in powder form obtained by a spray-drying process. It is well known that β-lactoglobulin, the major protein component in whey, is greatly affected by heat treatments, with consequences on its adsorption properties at fluid–fluid interfaces. This study concerned four whey protein powders obtained using spray-drying at four different air inlet temperatures (from 170 to 260 °C), leading to different levels of protein solubility, denaturation and end-use properties. After evaluation of the protein denaturation by HPLC, the emulsifying properties were studied through particle size parameters and rheological properties in relation with spray-drying parameters. Our results indicated that oil-in-water emulsions, stabilized by 5% (w/w) protein samples, exhibited a shear-thinning flow behaviour, and the harsher the spray-drying conditions (the higher the protein denaturation), the less viscous were the emulsions. The apparent viscosity of emulsions measured at 20 °C and 50 s⁻¹ shear rate was around 0.08 Pa s when containing whey proteins before drying, and around 0.05–0.018 Pa s after drying at air inlet temperatures from 170 to 260 °C. These differences in emulsion rheological properties were related to particle size effects, in regards to analysis of particle size distributions which showed a finer emulsion according to spray-drying intensity. Our results will be presented and discussed in terms of optimization of spray-drying process relative to globular protein surface activity.