Micron-scale mechanisms of the unit operations in the dairy industry : from vacuum concentration to spray drying
Similar to other sectors of food production, the dairy industry has undergone significant changes in recent years, for two main reasons : i) to minimize the production processes and obtain more biomimetic, high added-value products, such as infant formula, and ii) to design eco-efficient processes by reducing mass-energy consumption, particularly during maintenance and cleaning. These objectives represent a technological and scientific challenge, the achievement of which strongly depends on understanding the phenomena occurring during processing at the microscopic scale. To this end, a lab-scale approach mainly based on rheology and microfluidics has been adopted in our group to shed light on the physico-chemical mechanisms characterizing two unit operations typical of the dairy industry, i.e., vacuum concentration and spray drying.
The production of high-protein powders and infant formulas is a strategic sector of the dairy industry. To improve powder functional and nutritional properties, it is crucial to characterize the mechanisms governing the droplet-to-grain transition in a drying tower. In our studies, we investigated the drying of pendant [1,2] and sessile [3] droplets of dairy protein mixtures (whey proteins and casein micelles) to link sol-gel transition mechanisms, droplet morphology, and mechanical properties of the resulting dry matter. Our results highlight the critical role of whey protein stratification at droplet surface, thus influencing the formation of the so-called external “skin” and its buckling behavior, and rigidity. In addition to their potential industrial application, these findings provide insight into the physicochemical mechanisms governing drying in polydisperse colloidal systems.
The studies on vacuum concentration are currently focusing on a costly and unsolved problem of different sectors of food processing, i.e., fouling. Understanding and preventing fouling is crucial in the dairy industry to enhance both the efficiency of unit operations and product quality. While most studies have focused on heat exchangers, fouling mechanisms in falling-film evaporators remain largely unexplored despite their widespread use in milk powder processing. Coupling rheofluidic approach [4] and microfluidic devices that replicate falling film evaporator flow conditions, we directly observed fouling growth in dairy protein mixtures. Our outcomes reveal distinct mechanisms governing bulk protein aggregation versus surface deposition.
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1. Lanotte, L., Boissel, F., Schuck, P., Jeantet, R. & Le Floch-Fouéré, C. Drying-induced mechanisms of skin formation in mixtures of high protein dairy powders. Colloids Surf. Physicochem. Eng. Asp. 553, 20–27 (2018).
2. Yu, M. et al. Skin layer stratification in drying droplets of dairy colloids. Colloids Surf. Physicochem. Eng. Asp. 620, 126560 (2021).
3. Le Floch-Fouéré, C. et al. Crack patterns induced by auto-stratification in drying sessile droplets of dairy proteins. Colloids Surf. B Biointerfaces 253, 114761 (2025).
4. Grostete, M. et al. Exploring the formation of surficial whey protein deposits under shear stress by rheofluidic approach. Int. J. Biol. Macromol. 274, 133291 (2024).