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Conference Papers Year : 2023

Microscopic investigation of fouling mechanisms in dairy protein mixes under shear

Abstract

Thermal fouling is an unsolved and costly question for the dairy industry and consists in the accumulation of the solid fraction of a processed liquid stream on a stainless-steel surface due to the combined action of flow and thermal/concentration gradients. Understanding and preventing the phenomena related to thermal fouling is of paramount help to optimize the operation unit efficiency and to improve the quality of the products. Until now, most of the studies available in the literature focused on the fouling dynamics in heat exchangers and led to contradictory results based on the off-line analysis of the solid deposits. Conversely, the fouling mechanisms have been rarely explored in the evaporators despite their increasingly essential and sensitive use in dairy industry (e.g., infant formula production). The hypothesis explored in this work is that the initiation of the fouling process is not exclusively due to protein thermal denaturation in the liquid stream once a critical temperature is achieved (T>65°C), but also to the impact of the shear rate near the equipment walls. Dispersions of whey proteins with different overall concentrations were processed by rheometry, undergoing the range of temperatures (45-80°C) and shear rates (100s-1) typical of falling film evaporators in a wide temporal range (0-30min). The effect of the combined thermal and shearing action on protein denaturation/accumulation was evaluated on glass surfaces, by observing the formation and the development of the deposits (density, size, shape) at different local shear conditions using optical and digital microscopy. Particular attention was given to the observation of the early stage of the fouling process, characterized by the formation of initiation sites (i.e., unfolded proteins anchored to the surface) that favor the subsequent accumulation of deposits. The structure and the composition of these preliminary active deposits was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results provided an insight into the dependency of fouling mechanisms on key factors such as time, shear and solute concentration. Starting from this rheometry-based approach, the challenging next step will be to provide a direct observation of the fouling dynamics in dairy mixes by microfluidics.
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Dates and versions

hal-04180057 , version 1 (11-08-2023)

Licence

Attribution - NonCommercial - NoDerivatives

Identifiers

  • HAL Id : hal-04180057 , version 1

Cite

Margot Grostete, Msibi Zanélé Paméla, Françoise Boissel, Maude Jimenez, Romain Jeantet, et al.. Microscopic investigation of fouling mechanisms in dairy protein mixes under shear. XVIIIth Congress on Rheology ICR, https://www.erasmus.gr/microsites/1221/committees, Jul 2023, Athènes, Greece. ⟨hal-04180057⟩
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