Phd Proposal : Tannins and Oxidation in model-real matrix containing Protein, Interaction and Complexation monitoring.
35653 LE RHEU CEDEX
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
Socio-economic and scientific context:
Vegetal matrices have rising interest from the agri-food sector as promising alternatives for the food transition. To reach agroecological concerns, plant production in low input systems will rely on increase
plant defense toward both a-/biotic stressors. Such situation will trigger increased polyphenols and pathogenesis related proteins content in plant products. The polyphenolic and especially tannins
susceptibility to oxidation associated to the enriched proteic content will favored interaction establishment during transformation steps (flour, isolates…). Polyphenols oxidation lead to quinone
formation that interact with proteins through covalent (irreversible) and non-covalent (reversible) bounding. Even if some polyphenol-protein interactions might benefit to technico-functional properties,
it also can led to off-flavors. Despite their major effects on polyphenol-protein interactions, neoformed tannins structure remained poorly known
Assumptions and questions
What is the structure of newly formed tannins through oxidation process? Are the new structures dependent on the proanthocyanidin starting structure (extension unit nature, degree of
polymerization…)? How do these structural changes resulting from oxidation of proanthocyanidin modify their ability to form complex/conjugates with proteins? What are the determinants of the interactions
(non-/covalent) depending on the matrix composition and food processing steps ?
The main steps of the thesis and scientific procedure
The first objective is the better understanding of the oxidation reaction on condensed tannins and thus the effect of the matrix composition (pH, temperature, pression…) on neoformed structures. The
approach will be based on non-targeted LC-HRMS of vegetal matrix originated from agri-food transformation steps in the way to find oxidized tannin biomarkers. Proteins matrix differences
(quality/quantity) will enabled to have a glimpse on the proteins impact on the proanthocyanidins eactivity towards oxidation. Then, a design of experiment will focus on proteins and non-/oxidized
proanthocyanidins select according case of study (legume crops, astringency and salivary proteins, allergenicity, beverage fining…). This approach in model solution will provide a better understanding on
mechanisms and determinants of polyphenols-proteins interactions and resulting structures through non-/covalent bounding. Finally, chemometrics analysis on model solutions will confirm biomarkers
revealed through the LC-HRMS profiling of processed vegetal matrix.
Methodological and technical approaches considered
- Non-targeted metabolomics matrix analysis: UHPLC-DAD-HRMS (Exploris 240, Orbitrap)
- Conduct and monitoring of polyphenols’ oxidation in model solution
- Polyphenolic screening through both direct and depolymerization: UHPLC-DAD-MSn (LTQ-XL)
- Fluorescence spectroscopy, microcalorimetry, electrophoresis
- Chemometrics (PCA, (O)PLS-DA, multivariate tests)
- Proteomics
Training and skills
Master's degree/Engineering degree
Scientific and technical skills required by the candidate
Analytical chemistry and chemical reactivity knowledge and experiences as well as in vegetal biochemistry and properties in food. Desired experiences on separative and MS techniques on vegetal matrix. Skills in high throughput data treatment ans statistics. Ability to work in team and in project mode, writing and communication skills (English, willingness to perform / learn French).
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.
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