Protein-based strategies for fat replacement: Approaching different protein colloidal types, structured systems and food applications

In the last decade, food structuring has received considerable attention due to the concern of replacing trans and saturated fats with healthier alternatives without compromising neither technological nor sensorial aspects of food products. Moreover, sustainability topics, consumers' preference for natural ingredients and the molecular architecture displaying a myriad of techno-functionalities embolden the use of proteins. Therefore, a promising approach is to explore this biopolymer as a texture promoter in lipid-based systems, conveying an extra edge in nutritional, sustainable and technological values. A more in-depth comprehension should be cemented to fully harness the potential of proteins in developing soft matter intended for use as fat mimetic. High Internal Phase Emulsion (HIPE), High Internal Phase Pickering Emulsion (HIPPEs), emulgels, oleogels or even bigels can be used in such strategies. Essentially, the formation of such systems relies on the amphiphilic character of proteins. In this sense, the question that arises is how to optimize their solubility in oils to form oil-structured systems? Thus, for oleogel formation the challenge is to overcome the limited dispersibility of proteins in a hydrophobic environment. Therefore, face the growing interest and untapped potential in applying proteins in lipid media, a more wide-ranging picture of their colloidal form (e.g. native, microgels and protein-polysaccharide complexes or conjugates) affecting the structure-function relationship of proteins must be investigated. This review covers different strategies using proteins as building blocks to manufacture different structured systems. Finally, an outlook over the use of protein-based soft matter on an industrial basis is discussed, considering the challenges and perspectives.