Effects of gastric pH on in vitro gastrointestinal digestion of foods and meals using innovative magnetic resonance imaging (MRI) approaches

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INRAE presentation

The French National Research Institute for Agriculture, Food, and Environment (INRAE) is a major player in research and innovation. It is a community of 12,000 people with 272 research, experimental research, and support units located in 18 regional centres throughout France. Internationally, INRAE is among the top research organisations in the agricultural and food sciences, plant and animal sciences, as well as in ecology and environmental science. It is the world’s leading research organisation specialising in agriculture, food and the environment. INRAE’s goal is to be a key player in the transitions necessary to address major global challenges. Faced with a growing world population, climate change, resource scarcity, and declining biodiversity, the Institute has a major role to play in building solutions and supporting the necessary acceleration of agricultural, food and environmental transitions.

Work environment, missions and activities

Host laboratories:

IRM-Food research team, UR OPAALE, INRAE, Rennes, FRANCE
https://eng-opaale.rennes.hub.inrae.fr/research/research-teams/irm-food
BN research team, UMR STLO, INRAE, Rennes, FRANCE
https://eng-stlo.rennes.hub.inrae.fr/research/bn-group

ABSTRACT:
Solid food enters the stomach in the form of boluses made of particles of 0-5 mm in diameter. Depending on their structural and compositional properties, digestion of these particles can be limited by the diffusion of digestive enzymes within them, the resistance of microstructures to enzymatic attack (e.g. gluten, cell walls) or by pH conditions unfavourable to enzyme activity (buffering effect). The ability of MRI to characterise the composition and structure of food at different scales in a non-invasive and non-destructive way makes it a method of choice for monitoring digestion kinetics and improving our understanding of the mechanisms involved in the digestion of solid food particles.
The aim of this thesis is to study the mechanisms that limit the degradation of solid food particles and the release of their nutrients during in vitro digestion under MRI. Particular attention will be paid to the influence of gastric acidification kinetics, which are known to be highly variable between individuals (inter-individual variability or variability induced by the use of proton pump inhibitors), on gastrointestinal digestion kinetics. Semi-dynamic in vitro digestion of food particles, in a mixture and as individual food pieces, will be monitored by various MRI acquisition methods. It will be used to assess how physiologically relevant gastric pH variations affect the biochemical processes responsible for the disintegration of bread, cheese and tomato at various length-scales: molecular (NMR relaxation times), ~millimeter (voxel size) and ~centimeter (erosion of a food piece). The release of key food nutrients in collected samples will also be investigated.
The experiments will be performed on the 1.5 T whole body MRI imager (SOLA, Siemens) using original devices that has already been validated for performing in vitro digestion under MRI.

SUPERVISION & ENVIRONMENT:
The PhD student will be employed by INRAE and integrated into the teams of two research units: OPAALE and STLO (about 2 km apart), where all the equipment required for the thesis is available. The thesis will be co-supervised by Maja Musse (INRAE, UR OPAALE, IRM-Food team) and Steven Le Feunteun (INRAE, UMR STLO, BN team).
The PhD project is part of the ANR-funded Gastric-pH project. The PhD candidate will therefore take part in the regular meetings involving all project partners.

Training and skills

The ideal candidate will be a physicist or physical chemist with basic knowledge of MRI/NMR physics and signal/image processing. Skills or interest in applications in food science, nutrition and/or biology would also be appreciated. A good level of English is required

INRAE's life quality

By joining our teams, you benefit from (depending on the type of contract and its duration):

- up to 30 days of annual leave + 15 days "Reduction of Working Time" (for a full time);
- parenting support: CESU childcare, leisure services;
- skills development systems: training, career advise;
- social support: advice and listening, social assistance and loans;
- holiday and leisure services: holiday vouchers, accommodation at preferential rates;
- sports and cultural activities;
- collective catering.

How to apply

I send my CV and my motivation letter