Drying research : from physical and biological mechanisms to breakthrough innovation

International audience

English. One of the main concerns of the UMR STLO's Process - Structure - Functionality (PSF) team is to understand how the conduct of concentration/deconcentration operations affects the behaviour and properties of ingredients, and in return how the characteristics and properties of ingredients modify the performance and environmental impact of operations.Nowadays milk drying is no longer aimed simply at prolonging its shelf life, but at producing highly functionalised powders whose properties need to be perfectly controlled. To achieve this, a multi-scale approach is particularly relevant: the study of the evaporation of a drop has enabled us to understand the influence of the nature of the milk proteins during the transformation of the drop into a powder grain. The involvement of these proteins has direct repercussions on the structure of the particles and consequently on the properties of the powders obtained. These results make a conceptual contribution to a better understanding of the behaviour of milk constituents in a concentrated medium, which will ultimately make it possible to predict and control the quality of powdered products.Other research has used a simplified, low-cost patented process to address the drying conditions required for the growth and survival of probiotic bacteria. Unlike the conventional process, which requires an initial stage of culturing the micro-organism on an optimised medium (often non-food), followed by rinsing and resuspension in a new medium before spray-drying, the process developed involves drying directly on the culture medium. As well as increasing productivity, this simplification of the process eliminates any risk of contamination at intermediate stages.Finally, in the current context dominated by concerns about climate change, reducing energy consumption during drying is a priority for industries seeking to minimise their environmental footprint whilst controlling costs. Research has shown that replacing spray drying with a two-stage process (Poudre Sans Tour, PST), overconcentration and granulation, can reduce the energy footprint of dairy powder production. This result opens up new possibilities for the formulation of complex products, an interesting prospect for developing and optimising the new process for the sustainable production of dairy and food powders.