Formation of supermolecular assemblies on colloidal surfaces

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Foods are multiphase systems containing colloidal particles (protein aggregates, emulsion droplets). Biopolymers can interact with the colloid particles, creating supermolecular assemblies. Although we are starting to understand how to control these interactions, we are just at the beginning stages of the study of how they affect changes in stability, texture and microstructure. The challenge of relating colloidal phenomena to real foods also still remains. We are proposing to study the complex dynamics of exchanges at the interface in multicomponent systems, especially under processing conditions such as heat treatment and acidification. In an effort to work under conditions as close as possible to the real systems, biopolymer interactions need to be studied not only with traditional analytical tools, but also with novel techniques which allow measurement of the physico-chemical properties without disturbing the structure. In fact, a very difficult task is to study the incipient destabilization or gelation in mixed systems, as the very act of measuring their properties causes them to change the structure. We have successfully developed ways to measure these systems without disruption using ultrasound and diffusing wave spectroscopy. These techniques can measure concentrated, opaque samples, under quiescent conditions, with no need for dilution or any other sample disturbance. We demonstrated that the beginning stages of the interactions and the dynamics of aggregation can now be observed. Our laboratory is unique in Canada and in North America in this area of research and the use of these techniques. We are proposing to use model systems of increasing complexity to look at the effect of biopolymer interactions. This basic approach will allow us to better understand the parameters and interpret data from ultrasound and diffusing wave spectroscopy on concentrated food colloids. We will then be able to interpret the dynamics of interactions between polymers and colloids, and determine how these assemblies affect the behaviour of multi-component systems during processing. Our research outcomes will represent a turning point in our understanding of the formation of structure in food systems.