PhD Student Project
Controlling digestion kinetics through food micro structure design
Supervisors: Dr Charlotte Conn (RMIT University, Melbourne, Australia), Dr Amy Logan (CSIRO, Melbourne, Australia) and A/Pr. Juliane Floury (UMRSTLOINRA-AgrocampusOuest, Rennes, France).
This 3-year PhD student project will develop new capability in food digestion,by a deep understanding of the influence of food microstructure on enzymatic hydrolysisduring gastric digestion.
Food is a complex combination of chemically diverse structures, influenced by composition and processing. It is now largely recognized that the nutritional quality and function of the food material cannot be determined from compositional criteria alone (Turgeon and Rioux, 2011). Despite increasing interest to modulate food structure asa potential way to control food breakdown, nutrient release and absorption, little is known regarding the underlying mechanisms.
In previous studies, physical observations have been made relating the start and the end points of a food as it was consumed. That is, the initial macroscopic features of the ingested food, and the final delivered concentration of nutrients into the blood stream, such as amino acids, were measured as a function of time.
The most common hypothesis to explain the influence food structure on digestion rates is that the proteolysis may be limited by the pepsin activity within the protein structures formed in the stomach. It is known that the gastric juice penetrates the food matrix and assists in digestion, but how the acidity and enzyme of the gastric juice affect disintegration of food is still far from being fully understood. Moreover, while the functioning of hydrolytic enzymes is quite well understood in solution, the mode of operation of enzymes on solid substrates is still widely unknown (Blazek and Gilbert, 2010). There is, indeed, a real lack of methods that allow monitoring the evolution of food micro and nanostructure in the course of digestion.
This PhD project will follow the evolution of structures within the food matrices upon digestion, and the rate of enzyme diffusion in real time. For this, we will use advanced microscopy and high-resolution scattering techniques to build a complete description of the nanoscale structure. Small angle scattering of x-rays (SAXS) or neutron (SANS) are non-invasive and non-disruptive techniques which enable the study of the milk protein gels under realistic conditions (in situ) and provide bulk information with the scattering representative of the whole sample. Assoc. Prof Floury has recently adapted a confocal microscopy technique involving fluorescent recovery after photo-bleaching to measure diffusion coefficients of fluorescently labelled pepsin within dairy gels (Thevenot et al., 2017).
In parallel, the hydrolysis and particle breakdownkinetics of the dairy gels using in vitrogastric digestion will be characterized using biochemical and physico-chemical analysis. Both sets of results will enable the precise characterization of mechanisms for enzymatic food particle breakdown in the stomach, in order to further understand and control digestion kinetics.
Profile of the candidate:
Master or Undergraduate degrees with first class honours in physics, physical chemistry, chemistry, biophysics, medical physics, biomechanics, food science or nutrition. Experience in x-ray and/or neutron scattering techniques, the analysis of complex data and modellingpreferred.
A scholarship supported by CSIRO and RMIT University of $30,000 per annum will be awarded to the successful candidate for a period of 3-years.The student will beco-located at CSIRO Agriculture and Food (Werribee, Victoria, Australia) and RMIT University (City campus, Victoria, Australia).
The student will also receive funds to support an extended visit to the 'Science & Technology of Milk and Eggs' joint research unit of INRA-AgrocampusOuest in Rennes, France, to perform an experiment using confocal microscopy to follow enzyme diffusion in real-time (planned for early 2018).
The closing date for applications is 11:00pm on Thursday 17th August
Applications are open to both local (Australian citizens, permanent residents or New Zealand citizens), international and RMIT internal candidates.
Blazek, J. and Gilbert, E.P. 2010. Biomacromolecules 11, 3275-3289.
Thevenot, J., Cauty., C., Legland, D., Floury, J. 2017.
Food Chemistry. 223. 54-61. Turgeon, S. L. and Rioux, L. E. 2011.
Food Hydrocolloids 25 (8): 1915-24.