Food colloids and soft matter at interfaces

Our research is focussed on understanding how the surface of particles dictates the way they interact with one another. For example how the coagulation (aggregation) of natural milk protein particles (casein micelles) react with the introduction of enzymes or acid production of cheese or yoghurt. This layer might be just one molecule thick. 

These layers may represent a very small weight % fraction of the overall system, but their properties and how these change on processing can have disproportionately large effects on the properties of the whole system. In the example of cheese- making, enzymatic cleavage of one of the protein chains (of k-casein) at the surface of the milk protein particles (casein micelles) results in a slightly shorter chain sticking out from the surface of the particles, ‘magically’ resulting in rapid and complete clumping of all the casein micelles into curd. 

Or to take another example from milk, because the lipase enzymes that digest fat are water soluble, they digest the fat/oil droplets in milk from the outside inwards, i.e., at the interface between the oil and water. But before the lipases can do this, whatever else that is adsorbed at the surface of the droplets: proteins, lipids from natural membranes in the cow, etc., has to be swept away by another range of surface active molecules (bile salts) and conditioned by adsorption of other proteins (co-lipases) to the droplet surface. This removal of interfacial material can be easy or difficult, depending on a whole host of factors, including the nature of what it is, its processing, the presence of other food constituents in the diet that interact with it, as well as individual human variations in the type and timing of bile salt secretion, plus sequestering of bile salt by other components in the gut. 

Furthermore, the milk fat may be already trapped in a network (gel) of some other material (such as the casein network in cheese above), affecting the ease and speed with which lipases can get to the interface, plus the speed with which digestion products can exit the gel. Even then, the digestion products face another barrier –the mucus gel network lining the gut wall - before they are adsorbed into the blood stream. The pore size, cross-link density and therefore the strength of these gel networks affects the ease of their breakdown and the entry, exit and passage of other materials through them.

All these colloidal factors are operating naturally whenever we eat processed or non-processed food. Our research looks at how we can influence this process. For example, we can directly influence the rate of release and digestion of materials to change the rate of uptake of calories, nutrients or other dietary constituents (such as polyphenols, polyunsaturated fatty acids) that might have disease preventative (or harmful) effects. However, there are other factors that influence the flavour, texture even appearance of food that make us want to consume it in the first place. Colloidal structure and stability research must also consider the choice and preference of consumers, which means our research is closely tied to generic aspects of surface and interfacial science, rheology and therefore ‘soft matter’ - one of the most actively studied areas of physics, biophysics, physical chemistry, as well as food science.

Research team

If you are interested in collaborating with us or joining our research team, please get in touch. View all members of the food colloids and soft matter at interfaces theme.

PhD projects

We have opportunities for prospective PhD students. Potential projects can be found in our postgraduate research opportunities directory.