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Theses

Évaluation et prévision de l’activité antimicrobienne des conservateurs dans des formulations cosmétiques

Abstract : Most cosmetic products are susceptible to microbiological spoilage, which is particularly due to the high-water content in its composition, to the room temperature storage and to the consumer usage. The range of usable preservatives is reduced, in particular because of the tightening of the regulation. The objective of this PhD is thus to better understand, predict and optimize the efficiency of the preservation systems in cosmetic formulas. Moreover, we aimed to understand the role of the matrix (composition and structure) on the spatial distribution of Staphylococcus aureus in cosmetic matrices, and to implement a rapid method able to predict the action of the preservatives within these matrices. The Challenge-test is the referenced method for evaluating the antimicrobial protection of a cosmetic product but it has a main limitation which is relative to the time-consuming protocol and to the duration of the whole test.Hence, we first identified the determinants of the spatial distribution of Staphylococcus aureus artificially inoculated in cosmetic formulas using a method combining confocal laser scanning microscopy (CLSM) and image analysis. We demonstrated that the higher the viscosity of the formula and / or the higher the bacterial hydrophobicity, the more heterogeneous the bacterial spatial distribution. The heterogeneity of the spatial bacterial distribution of the formula can induce variability in the enumeration results during Challenge-tests. A rapid method was then developed to assess and predict the action of preservatives in cosmetic formulas. This method is based on both the acquisition by CLSM of bacterial inactivation datasets over short periods of time and the implementation of mathematical inactivation models.Thus, it was possible to predict the number of bacterial logarithmic reductions on long times that are relevant to challenge-test duration. This tool should allow the cosmetic industries to save time in optimizing the antimicrobial protection of cosmetic formulas.
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Submitted on : Monday, July 25, 2022 - 5:23:18 PM
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  • HAL Id : tel-03738124, version 1

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Samia Almoughrabie. Évaluation et prévision de l’activité antimicrobienne des conservateurs dans des formulations cosmétiques. Microbiologie et Parasitologie. Université Paris-Saclay, 2020. Français. ⟨NNT : 2020UPASA014⟩. ⟨tel-03738124⟩

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