Proteins as Building Blocks for Oil Structuring
In this chapter, we discuss how proteins can be used as building blocks for oil gelation. Being amphiphilic, proteins have the potential to structure both aqueous and organic solvents. However, owing to their high hydrophilic nature as a result of their tertiary structure, globular proteins cannot directly be used as a structuring agent for oil. To enhance their dispersibility, first initial protein building blocks are created by heat-induced aggregation, which increases their surface hydrophobicity. A solvent exchange procedure is then used to introduce these protein building blocks into liquid oil. As the samples are continuously present in a wet state during this procedure, the protein aggregates become finely dispersed in the oil, which allows for efficient network formation. Similar to hydrogels, protein oleogels can be obtained with different microstructures, from fine-stranded to coarse, and from transparent to opaque. The mechanical properties can be controlled by the type of network formed and the properties of the initial building blocks. Their properties can vary from hard and very brittle to soft and spreadable. The network formation is governed by a delicate balance of hydrophobic interactions with the surrounding hydrophobic solvent, and interactions of hydrophilic nature between the protein aggregates. As the properties of the protein oleogels can easily be altered, protein have great potential to be used as structuring agents for oil in commercial applications, and may be used in the food, pharmaceutical or cosmetics industries.