Mechanical and thermal segregation of milli-beads during contact heating in a rotary drum. DEM modeling and simulation

[EN] The flow mechanics and heat transfer phenomena within a bed of milli-metric size spherical beads rotated and heated by contact in a horizontal drum were simulated by means of commercial discrete element software EDEM. Mono-dispersed and bi-dispersed beds (two particle sizes or two particle densities) were considered. The mechanical segregation index (standard deviation of local bed compositions) and the thermal segregation index (standard deviation of beads temperatures) were calculated for the different types of bed and same operating conditions. The thermal segregation was found to be enhanced by mechanical segregation and was much stronger for bi-dispersed beds than for monodispersed one.Mesnier, A.; Rouabah, M.; Cogné, C.; Peczalski, R.; Vessot-Crastes, S.; Vacus, P.; Andrieu, J. (2018). Mechanical and thermal segregation of milli-beads during contact heating in a rotary drum. DEM modeling and simulation. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 107-114. https://doi.org/10.4995/IDS2018.2018.7423OCS10711

Study and optimization of freeze-drying cycles of a model probiotic strain

[EN] This work is based on the experimental study of the freeze-drying process to understand the impact of numerous factors on the survival rates of a model probiotic strain of Lactobacillus casei type. With the aim to find out if cell density in the matrix and survival rates are linked, we have studied the location of the cells after freeze drying inside a porous matrix composed of a lactose basis with a polymer, the polyvinylpyrrolidone (PVP) in various amounts. The best survival rate were obtained at slow freezing rate for a formulation containing 5% (m/V) of lactose and 5% (m/V) of PVP.Verlhac, P.; Vessot-Crastes, S.; Degobert, G.; Cogné, C.; Andrieu, J.; Beney, L.; Gervais, P. (2018). Study and optimization of freeze-drying cycles of a model probiotic strain. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 635-642. https://doi.org/10.4995/IDS2018.2018.7400OCS63564

Influence of operating conditions on the freeze-drying of frozen particles in a fixed bed and modelling data

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Study and optimization of freeze-drying cycles of model probiotic strain of lactobacillus casei type

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Experimental study and optimization of freeze-drying cycles of a model Casei type probiotic bacteria

International audienceThe objective of this paper was to present experimental results concerning the optimization of freeze-drying cycles of a model type casei probiotic bacteria with water based formulations using lactose and polymer (PVP) as cryo/lyo protectants. First, we investigated the influence of different formulations and of different freezing protocols (freezing rates and pre-freezing treatment) on the viability of the model probiotic strain after the freezing step. Secondly, the heat transfer coefficient was characterized by an overall heat transfer coefficient determined with pure water. In our very soft operating conditions - total gas pressure from 10 to 30 Pa and shelf temperature from −20 °C to 10 °C – the sublimation process was mainly controlled by the heat transfer from the vial surroundings to the sublimation front that take place by conduction, by contact at the vial bottom and by radiation from the self and from the chamber walls. Next, as concern the single freeze-drying process approach, with the preselected formulation - composition and freezing rate - we studied the influence of the sublimation operating parameters, namely the total gas pressure inside the sublimation chamber and the shelf temperature on the bacteria survival ratios and on the sublimation times. In agreement with previous literature data, we observed that the sublimation rate increased with the increasing total gas pressure and the shelf temperature. It is worth to note that these experimental data have shown that sublimation times could be reduced by about 40% without reducing the bacteria viability by realizing the sublimation at temperatures slightly higher (about 4 °C) than the classical limit temperatures encountered during the freeze-drying processes of thermosensible biological systems like vaccines i.e., the vitreous transition temperatures of the formulations

Etude, expérimentation et optimisation des cycles de lyophilisation d'une souche de probiotiques

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Study and optimization of freeze-drying cycles of model probiotic: Morphology characterization of Lyophilisates by SEM

International audienceThese experimental data are concerning the optimization of freeze-dryingcycles of a model type Casei probiotic bacteria with water based formulationsusing lactose and polymer polyvinylpyrolidone (PVP) as cry/lyo protectants.After a previous study devoted to the influence of the main freeze-dryingparameters (freezing rates; shelf temperature; total gas pressure) on thebacteria survival ratios, this paper reports some morphological data obtainedby scanning electron microscopy (SEM) with the final lyophilisates.The numerous and original SEM images realized with different formulationsof water binary or ternary mixtures with fixed operating conditions proved tobe very useful to explain and to understand the different bacteria survivalratios observed.,Thus, with bacteria or micro-organisms systems, this powerful investigationmethod of characterization of lyophilisates morphology should be morelargely used in the future for setting up the optimal formulations parameters(composition) and the connected operating physical parameters of freezedrying steps (freezing rate, shelf temperature, total gas pressure)

Optimization of freeze-drying process for casei type probiotic strain water based formulations

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