Modulation of metallic oxide particle behaviour in a formulation: physicochemical and/or sensory properties of emulsions as a tool to identify particles interactions within the matrix

International audienceParticles of metal oxides such as silica (SiO2), alumina (Al2O3) or titanium dioxide (TiO2) are nowadays widely used in manufactured products. The interest of these solid particles lies in the possibility tovary their size (a few nanometers to several micrometers), their shape, and their state of aggregation, as well as their specific surface. In addition, these metal oxides are good candidates for surface modification (coating with other metal oxides, silanization) to also modulate their surface properties [1-2].Thus, incorporated in a complex medium such as an emulsion, these solid particles, due to their varied physicochemical properties, will be able to interact with all the constituents of the matrix. This represents asubject of great scientific interest, from both applied and fundamental point of view. Depending on its surface properties, the particle can manifest more affinity with the continuous phase, the dispersedone, or can be placed at the interface [3]. In the latter situation, the particle can act as a surfactant and can even replace the molecular surfactants conventionally used.The aim of this study lays on its multiscale approach: from microscopic scale through the investigation of the ingredients interactions (guided by the type of particle used) to macroscopic scale with the characterization of stable, homogeneous and totally emulsified systems (as it was a required condition to provide an adapted system for macroscopic evaluations). Rheological, textural and sensory behavior, as well as emulsion colloid size and size distribution, were used as a tool to identify the role of the particles on the matrix organization.One objective was to find the emulsions optimal formulation process and composition to accomplish the desired requirements for this study.The obtained results clearly showed the importance of the particle properties in emulsion formation and stabilization. Interactions created inside the matrix were governed by the specific surface andthe coating type of the particles. Thus, the modulation of the emulsion can be possible relying on the particle/emulsifier/oil phase interaction and ratio.[1] S. Björkegren, L. Nordstierna, A. Törncrona and A. Palmqvist, Journal of Colloid and Interface Science, 2017, 487, 250.[2] C. Picard, A. Larbot, E. Tronel-Peyroz and R. Berjoan, Solid State Sciences, 2004, 6, 605.[3] B. P. Binks, Current Opinion in Colloid & Interface Science, 2002, 7, 21

Objectiver nos perceptions sensorielles : le toucher et le parfum des produits cosmétiques

International audienceL’évaluation sensorielle en cosmétique vise à décrire les propriétés organoleptiques d’un produit avec nos sens. Les perceptions tactiles et olfactives jouent un rôle prédominant dans l’appréciation d’un produit qu’il s’agisse du plaisir procuré ou de l’évaluation de son efficacité. Néanmoins, l’évaluation sensorielle est une approche complexe qui mêle des jugements subjectifs à des caractéristiques objectives de la formule cosmétique. Il est indispensable mais pas toujours évident de dissocier ces deux dimensions lors des tests réalisés avec des panels d’évaluateurs. Nous illustrerons à travers divers exemples comment objectiver au mieux les caractéristiques d’un produit par une approche sensorielle et l’intérêt dans une démarche innovante de développement d’ingrédients ou de produits cosmétiques. La confrontation à des approches instrumentales prédictives sera également évoquée tant pour évaluer la texture que le parfum dans un souci d’objectivation. Mais l’odeur et la texture sont rarement évaluées séparément et loin d’être indépendantes, ces deux perceptions s’influencent l’une l’autre

Impact de la structure de gels composites à base de polyosides sur la libération d'arôme : exemple des bases de fruits-sur-sucre

Diplôme : Dr. d'UniversitéThe main objective of this study was to understand the respective rôle of the structure of a food product and of the physicochemical interactions on flavour release. For that purpose, fruit préparations hâve been chosen as model matrices. Those matrices contain a polysaccharide as gelling agent, a cross-linked waxy corn starch (1.4%), a high sucrose content (35%), an acidic buffer and a strawberry aroma (17 molécules). Four matrices were developed by modifying either the composition or the concentration in gelling agent: two matrices of similar texture containing either LM pectin or carrageenan, and two carrageenan based matrices with différent gelled structures. In a first step; two complementary tools were used to characterise the structure of the model matrices: rheology and confocal laser scanning microscopy. Heterogeneous composite structures were shown ascribed to the procédure applied for the préparation of this kind of product. To investigate flavour release; an instrumental approach has been favoured in order to study separately the kinetic phenomena that can occur during the release in différent conditions. The distribution of the aroma molécules in the matrix gel was considered. The diffusion coefficients of the aroma molécules were measured directly using NMR-PFG-DOSY. The partition coefficients were determined by way of the phase ratio variation method. Thèse thermodynamic and kinetic parameters hâve been used to interpret the release profiles obtained for the différent aroma molécules in static and dynamic conditions. It has been shown that pectin and carrageenan display similar flavour release whereas the structure of the matrix has an important effect. An increase of the rigidity of the gel induces a decrease of both the rate and the amplitude of flavour release; in link with the réduction of the diffusion coefficient.Le principal objectif de cette étude est de comprendre la part respective de la structure d'un produit alimentaire et des interactions physicochimiques sur la libération de composés d'arôme. Pour cela, des bases de fruits-sur-sucre ont été choisies comme matrices alimentaires modèles. Ces matrices contiennent un polyoside utilisé comme agent gélifiant, un amidon de maïs cireux (1,4%), ainsi qu'une forte teneur en saccharose (35%), un tampon acide et un arôme de fraise (17 molécules). Quatre matrices ont été développées en faisant varier le type et la teneur de l'agent gélifiant : deux matrices de texture similaire contenant soit de la pectine LM, soit du carraghénane et deux matrices à base de carraghénane ayant différentes structures gélifiées. Dans un premier temps, deux techniques complémentaires ont été mises en œuvre pour caractériser la structure des matrices modèles : la rhéologie et la microscopie confocale. Des structures composites hétérogènes ont été mises en évidence directement en lien avec le mode de préparation utilisé pour ce type de produit. La libération des différentes molécules composant l'arôme de fraise a été étudiée d'un point de vue physicochimique afin de distinguer les différentes étapes qui interviennent lors de la libération des arômes sous différentes conditions. La distribution des composés d'arôme dans la matrice en fonction de sa composition a été abordée. Les coefficients de diffusion des composés d'arôme ont été mesurés de façon directe en utilisant la RMN-PFG-DOSY. Les coefficients de partage ont été déterminés par la méthode de variation de ratio de phases. L'ensemble de ces paramètres thermodynamiques et cinétiques a été utilisé pour interpréter les profils de libération obtenus pour les différents composés d'arôme en conditions statique ou dynamique. Peu de différences ont été mises en évidence entre la pectine et le carraghénane alors qu'il a été montré que la structure affectait largement la libération des composés d'arôme. Une augmentation de la rigidité du gel a pour conséquence une réduction à la fois du taux de libération et de la quantité libérée, ceci étant relié à une diminution du coefficient de diffusion

Matières premières cosmétiques : Ingrédients sensoriels – Volume 1 : le toucher, la vision, le goût,

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Matières premières cosmétiques : Ingrédients sensoriels

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Characterisation of spreading and penetration of ingredients used in cosmetic emulsions

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Impact of emollients on the spreading properties of cosmetic products: A combined sensory and instrumental characterization

International audienceThis study deals with the impact of emollients on the spreading properties of cosmetic products using a combined sensory-instrumental approach. To that purpose, three esters and one silicone were selected and incorporated separately into an oil phase. Different cosmetic o/w emulsions were then prepared with these different oil phases. Both of them were analyzed by instrumental techniques and in vivo sensory analyses. A significant effect of the emollient used was established in emulsions and in oil phases as well. Concerning emulsions, results reveal a clear correlation between in vivo spreading evaluation and friction coefficient parameters measured by texture analyzer, despite a fairly low correlation coefficient (Pearson coefficient = −0.78). Concerning oil phases, characterization of spreading was done by monitoring the contact angle relaxation of a drop of solution after deposition on a flat PMMA surface whereas sensory procedure was based on spontaneous spreading of oil phases onto the skin. Finally, good correlations between in vivo sensory analysis and instrumental measurements of both oils and emulsions were found, thus promising the possible development of predictive tools to evaluate spreadability

Impact of the composition of polysaccharide composite gels on small molecules diffusion: A rheological and NMR study

WOS: 000274095800047 ; http://www.elsevier.com/locate/foodresInternational audienceThe gelation mechanism of carrageenan depends on the amount and nature of the polysaccharide, and is cation sensitive. From a theological approach, this specificity leads to different textural properties. In composite gels with carrageenans, starch and sucrose, the presence Of kappa/kappa 2-carrageenan, even at low levels, has an impact on textural and structural properties. In this study, theological and diffusion NMR measurements were performed on composite gels to probe gel structure at the macro- and micro-scale. Variations were made in the gel composition by varying the carrageenan content and the nature of the polysaccharide and cations. We showed that all the factors that increased the rigidity of the composite gels - polysaccharide content and specific cations - decreased significantly the diffusion of small molecules such as sucrose and ethyl butyrate. (C) 2009 Elsevier Ltd. All rights reserved

Spreading behavior of cosmetic emulsions Impact of the oil phase

International audienceBackground Emollients are an important ingredient in personal care products, they are currently prescribed in skin disorders like eczema, which affects up to 30% of children in developed countries. Methods The aim of the study was to investigate the impact of two emollients (stearic acid and isohexadecane) and their mixtures in the spreadability and frictional effect on films obtained from oil-in-water emulsions. Rheological, textural, sensory and tribological analysis were performed on human skin and artificial substrates. Results The emollients ratio influences the spreading behavior of emulsions more isohexadecane in the oil phase easier to spread the product on the skin. Moreover, significant correlations were obtained for the spreading behavior obtained by textural measurements on artificial substrates and sensory analysis (Pearson coefficient = −0.871). The results obtained by frictiometer showed different developments over time after product application the friction values increase with the stearic acid concentration in emulsion. Discussion This study showed the importance to consider the emollient properties when one emollient is used in the emulsion, but especially their interactions, when several emollients are used, to better understand and anticipate their behavior. First, spreading was governed by the consistency of the emulsion, particularly impacted by the emollients ratio. But then, in a long-time spreading, when the emulsion broke down and residual film was formed, a particular interaction with skin influenced the spreadability. It appears that not only the physical state of the emollient but also its chemical nature, physical state, polarity, temperature might explain these phenomena. © 2018 Elsevier Lt

Innover en formulation cosmétique : outils de prédiction des propriétés tactiles

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