The effect of operating conditions on the physicochemical characteristics of whey protein–based systems

The uptake of proteins is highly recommended, mainly for athletes, elderly people and patients with serious diseases like dysphagia. In this work, whey proteins were used for producing two kinds of aqueous materials: suspensions of proteins, in the native form, and gels, obtained by protein denaturation. In the first system, proteins are used as interfacial active ingredients or as thickening agents of the aqueous phase, whereas in the second one they are used as structuring agents. These protein-based materials show very different rheological and microstructural behaviour even at the same concentration. In the case of an undenatured system, a growing protein fraction resulted in an increased dimension of their aggregates and all investigated systems exhibited a liquid-like behaviour with a viscosity independent of shear rate and well described by a Krieger-Dougherty model. In the case of thermally denatured systems, it has been observed that, at increasing protein content, aggregates evolve towards a continuous gel network with a fractal behaviour. Both systems have been modelled, according to their specific behaviour, with the aim of proposing equations suitable to relate macroscopic properties and microstructure, useful for designing new food products with predictable properties for different industrial uses.