Food colloids and soft matter at interfaces
Our research focuses on understanding the physical chemistry of complex food systems and the macromolecules that structure food. We seek to understand how the surface of food particles dictates the way they interact with one another.
All food is colloidal, i.e., consists of collections of particles of some sort or another: oil droplets (emulsions) air bubbles (foams) starch granules, cell walls etc., plus all food is processed in some way. Although all these particles (solid, gas or liquid) are composed of molecules, at many levels it is the particulate nature of food that has the most direct effects on the perception, acceptability, digestibility and nutrient release of the food.
By particulate nature we mean the size, shape and state of aggregation of the particles, i.e., whether the particles remain separate or are stuck together, strongly or weakly. Most food processing (storage, atmosphere, freezing, chilling, cooking, mixing, blending) affects this particulate nature. Furthermore, on consumption and digestion particle size, shape and composition varies as the food is mechanically broken down (disaggregated) in the mouth or aggregated via the action of saliva and mucus, or dissolved via the action of enzymes.
Our research centres on how to understand and control better the properties of emulsions, foams and dispersions of all sorts of other particles, large and small. This includes:
- Flow of heat and matter in the cooking, drying, chilling and freezing
- Food texture (smoothness, creaminess, crumbliness, crunchiness, etc.) including the relationship between mouthfeel (including friction and tribology) and food structure
- Quantification of consumer preference and perception
- Application of invasive or non-invasive ultrasound to modify food (e.g., crystallization in chocolate) and investigate its internal structure (e.g., creaming, sedimentation, separation, crystallization)
- Design of food structure to influence appetite (satiety), digestibility and controlled release of nutrients and nutraceuticals, involving work on gels, microgels and solid lipid nanoparticles and colloidosomes.
All these areas are investigated through combinations of experiment, theory and computer simulation. We work closely and have many joint projects with colleagues in the other research groups in the School.
Because most food (colloid) behaviour depends on the way particles interact (e.g., renneting or acidification of milk for cheese or yoghurt production) a large part of our research is concerned with understanding the interfaces between particles. In other words, the very thin regions that constitute the surface of the particles, which means our research is closely linked to generic aspects of surface and interfacial science.
Similarly, since food texture is ultimately dependent on the strength of the interactions between the particles, a lot of our research is closely connected to the generic world of rheology – the science of the flow and deformation of matter. Colloid science, rheology, surface and interfacial science are all part of the generic science research that has become known as ‘soft matter’ and is one of the most active areas of study of physics, biophysics, physical chemistry, as well as food science.
We work closely with leading physicists and chemists in this area as well as interaction with many food and non-food companies, for example through the Soft Matter and Functional Interfaces (SOFI) Centre for Doctoral Training.
We have been involved in ground-breaking research involving:
- The crystallization of fats in margarine manufacture that have been applied to chocolate but also crude oil refining and pharmaceutical ointments and creams
- Developments in the theory and instrumentation of the propagation and attenuation of electromagnetic radiation in complex food matrices that have led to the co-invention of the Ultracane blind aid
- Development of a new harmonised European standard of gastric in vitro models of digestion (INFOGEST) allowing better understanding of digestion research finding around the world
- Acting as consultants to many companies providing better understanding and solution to many processing and stability problems, for example foam stability in ice cream and other confectionary products, drying and processing of condiments and dressings, in combination via TSB and KTP funding.
Links with Industry
We work closely with many major companies and also small and medium enterprises (SMEs), via Consultancy, their direct sponsorship of PhD students, Research Council Industrial PhD CASE awards, SOFI CDT PhD students and direct sponsorship and co-sponsorship (with EU Framework funding, EPSRC, BBSRC, MRC, healthcare charities, etc.) of postdoctoral research.
The following list of major collaborators, (past and present), which is by no means complete includes: Akzo-Nobel; Arla Foods; Astra-Zeneca; BBSRC; Cadbury-Schweppes; Dairy Crest; GlaxoSmithKline; ICI; Mars; Mondelez (Kraft); Nestle; PepsiCo; Procter & Gamble; Shell Oil; Snow Brand Milk Company; Syngenta; Unilever.
Our laboratory is equipped with various specialist pieces of equipment including: interfacial rheometers; surface tension apparatus (static and oscillatory Wilhelmy plate and drop/bubble shape); contact angle; Langmuir troughs; light microscopy; Brewster angle microscopy; atomic force microscopy (AFM); confocal laser scanning microscopy (CLSM); ultrasound microscopy; in-house small and wide angle X-ray scattering (SAXs & WAXS) plus special access to faculties at Diamond; light scattering apparatus for particle sizing and electrophoretic mobility of aqueous and non-aqueous dispersions; UV/Vis spectrophotometry; Differential scanning calorimetry (DSC); controlled stress rheometers; texture analysers; tribometers; Foamscan and specialized bubble-forming rigs and pressure drop apparatus for foam stability measurements. Ultrasound velocity meters and the Acoustiscan apparatus for monitoring creaming/sedimentation. In vitro digestion systems and tissue culture faculties. We also have access to world leading electron microscopy facilities.
We are part of the White Rose High Performance Computer initiative, allowing access to the state of art computing facilities at the Universities of Leeds, Sheffield and York for implementation of in-house and open access code for the latest Monte Carlo and Brownian Dynamics simulations.
View all members of our research group, our research projects and publications.
We have opportunities for prospective postgraduate researchers. Find out more.
If you would like to discuss an area of research in more detail please contact the Research theme lead: Professor Brent Murray