MULTIDISCIPLINARY PH.D POSITION BETWEEN STLO (RENNES), FAST (ORSAY) AND LGC (TOULOUSE)
Multi-scale exploration of the drying dynamics of dairy colloids and their rehydration
Keywords : colloids, liquid-solid transition, evaporation kinetics, drying, dairy proteins APPLICATION BEFORE JUNE 28TH
Starting date : September-December 2024
Research description
Drying is a key stage in dairy processing, with 50% of collected milk dry matter currently being converted into powder. Due to the still relatively empirical control of the drying process, problems are encountered on an industrial scale, both in terms of product properties (non-conformity with expected properties, e.g. rehydration) and process performance (e.g. sticking). Indeed, the mechanisms of particle formation during spray drying are not yet fully understood, the drying chamber being a “black box” making on-line observation of droplet-particle formation impossible.
We therefore aim to develop a multi-scale physics approach that brings together two complementary approaches in a single, original scientific approach :
– a local approach, with detailed analysis of elementary phenomena based on fundamental laws and principles ;
– a systemic approach, integrating phenomena on a process scale, right down to rehydration properties in our case.
This exploration of drying dynamics represents a relevant method for observing the drying phenomenon directly, flexibly and in detail, and for understanding the influence of different colloids on the characteristics of the products obtained. Thus, the study of drying in a confined environment represents an interesting means of gathering new information on the behavior of matter in a concentrated state, consistent with what can be observed at higher scales.
The research questions addressed in this Ph.D. project will follow a deductive logic, from the observation of the phenomenon to its physical interpretation :
1. Direct observation of the organisation of dairy colloids during drying under controlled conditions.
What is the specific role of constituents preferentially involved in self-stratification mechanisms during evaporation of dairy colloidal dispersions ?
2. Physical interpretation of the various stages of the drying dynamics using model colloids. What are the mechanical and rheological parameters that govern the solid-liquid transition in dispersed colloidal systems ?
3. Transfer of knowledge acquired in 1D to 3D systems of binary colloid mixtures. What is the impact of stratification on the formation of interfacial skin during the drying of drops of colloid mixtures (dairy and model) ? How can we link the morphological characteristics of powder particles and their reconstitution in water, by characterizing water diffusion on the surface of the particles ?
