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Increased protein consumption gives rise to various health benefits. High-protein intake can lead to muscle development, body weight control and suppression of sarcopenia progression. However, increasing the protein content in food products leads to textural changes over time. These changes result in product hardening over time and several negative sensorial attributes such as rubbery and dry mouth feel. This thesis describes the role of structuring to control the rheological and mechanical properties of high-protein model foods. By altering the internal structure of the model systems, textural properties of the model systems at initial stage (fresh products) can be improved. Content of this thesis can be distinguished into four parts. The first part reviews existing studies related to high-protein foods. The effects of ingredients and processing were evaluated with respect to food products having a high protein content. Some studies indicated typical problems occurring in products or model systems with an increased protein content such as product hardening over time. Ingredients that might be added to ameliorate product properties were plasticizers, peptides made from whey proteins, disulphide reducing agents, and components that block the free thiol groups in proteins. This part provides guidelines for structuring high-protein foods aimed at avoiding or reducing the unfavourable changes in properties over time. Concentrated proteins in their native (unmodified) form can be replaced by protein domains or structural elements with altered properties. These domains or elements mitigate the changes in product structure, resulting in a product that is softer than the one made from native proteins only. The second part focuses on the structural elements made from whey protein isolate (WPI), namely WPI aggregates and WPI microparticles. WPI aggregates were formed by different heating conditions at neutral pH. Generally, a higher concentration and a higher temperature resu