Modulating protein interaction on a molecular and Microstructural level for texture control in protein based gels

The exploration of microstructures and textures of protein based systems is essential to understand (oral) breakdown properties and thereby textural aspects, or macroscopic functionalities such as water holding. Upon structure breakdown, the applied energy (W) is primarily directed towards fracture (Wf) for particulate gels. For stranded gels the applied energy is either elastically stored (Ws) or dissipated (Wd). The energy balance can then be denoted as W= Ws+Wd+Wf.1 The fore mentioned mechanical properties have been shown to relate to texture perception that may go from ‘spreadable’ to ‘crumbly’ for particulate and stranded networks, respectively.2,3 Understanding of how to control the energy balance with regard to microstructure and texture perception is of key importance for the food industry to modulate their products towards desired sensory properties, especially when new (alternative) protein sources are involved. Texture is to a large extent determined by the properties of the structural elements and their mutual interactions. These structural aspects stem from the aggregation behaviour of the individual proteins, which in turn is determined by the molecular characteristics and their ability to interact during processing. Subsequently, an assembled microstructure may consist of molecules (nm) and protein molecules that are assembled into flexible fine stranded structure elements (0.1-5 mm), and coarse stranded or particle shaped structure elements (5-50 mm). At any length scale, protein (structure elements) can be subjected to (food grade) chemical or enzymatic modification to tune their function in a spatial network. Up to now, this was however only done for proteins at a molecular level. Functionalization of specific structure elements and their interactions is a tool in understanding which length scales are relevant for tuning texture and breakdown properties. The type, shape and dimensions of these structure elements determine the efficiency and gel strength of the established spatial network. Hence, this work sketches the potential of different types of structure elements made from gelatin, whey protein and soy protein to direct macroscopic behaviour is discussed. On a molecular scale, modulation of gelatine is performed to alter its assembly into fine stranded networks and the subsequent macroscopic breakdown behaviour. Modification of whey protein is performed on an aggregate level to show the efficiency of thiolation of different supramolecular structures (fibrillar and amorphous aggregates) with regard to gelation propensity. On a microstructural level, particulate soy protein networks are tuned through the presence of calcium salts for their fracture behaviour. We show that control over texture and macroscopic properties can be obtained by modulation of protein functionality at different levels of protein organization.