Prinzipien der Herstellung und Stabilität von Emulsionen

Schubert, Helmar; Armbrüster, H.

doi:10.1002/cite.330610906

Cited by 31 publications

(15 citation statements)

References 11 publications

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“…Once the minimum of surface tension is reached, the corresponding concentration of emulsifier equals the CMC. 27,28 The interfacial area is then completely coated with a monolayer of emulsifier at dynamic equilibrium. Excess emulsifier molecules form reversible globular micelles which act as a reservoir for the dynamic exchange at the interfacial area and which may interact with aroma molecules.…”

Section: Results and Discussion Critical Micelle Concentrationmentioning

confidence: 99%

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Influence of oil‐in‐water emulsion characteristics on initial dynamic flavour release

2003

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Properties of oil-in-water (O/W) emulsions affecting initial dynamic flavour release were studied in real time considering mouth conditions. Aroma molecules from different chemical classes at concentrations typically present in beverages were used. The emulsion droplet diameter showed no significant influence on the dynamic flavour release. No barrier properties of the emulsifier were found, as the flavour release from equilibrated emulsions flavoured via either the oil phase or the aqueous phase showed no significant difference. Emulsifier concentrations above the critical micelle concentration did not influence the release. Even though the chemical composition of the lipids had considerable influence on flavour release, phase transition during equilibration from the liquid to the solid state insignificantly affected the initial dynamic release process.

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Section: Results and Discussion Critical Micelle Concentrationmentioning

confidence: 99%

“…27 Using a plot of emulsifier concentration versus surface tension, the CMCs for the emulsions containing different fractions of oil were determined graphically. 28 The viscosity and the droplet size distribution of all finished emulsions were determined.…”

Section: Determination Of Critical Micelle Concentration Of Tween 80mentioning

confidence: 99%

Influence of oil‐in‐water emulsion characteristics on initial dynamic flavour release

2003

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“…Since primary particles in the gel interact strongly with each other but are not rigidly connected, it is assumed that the gel's breakup behavior is similar to that of a highly viscous liquid. The concept of the Weber number [4], in which the surface tension of the liquid counteracts the deformation and, finally, the rupture of a droplet in turbulent flow, was expanded by Arai et al [3] for highly viscous liquids. The resistance of the liquid against deformation due to surface tension and viscosity was described by a spring and dashpot model.…”

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confidence: 99%

Inorganic Precipitated Silica Gel. Part 2: Fragmentation by Mechanical Energy

2010

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Precipitated silica (SiO 2 ) is industrially produced by mixing a silicate solution with acid in a semi-batch process. Polycondensation of monomeric silica leads to the formation of particles which aggregate and eventually form a particulate gel. However, this is instantly fragmented by the mechanical energy input caused by the stirrer. Shrinkage and compaction of these fragments lead to the final product aggregates. It is the aim of this study to enable tailoring of the structure and size of these product particles via the process parameters. In the present paper this is achieved by varying the stirrer speed. It can be shown that there is an analogy between the behavior of the gel and that of highly viscous liquids. Unexpectedly, however, the fragment size can not be reversibly controlled by the power input. The influence of the process parameters on the strength of the gel has been described in the first part of this series [1]. IntroductionAmorphous precipitated silica is a widely used filler and is industrially produced in large quantities. The results presented here contribute to the control of aggregate size and structure of precipitated silica via the process parameters. The findings are presented in a series of two papers, the first of which is dedicated to gelation [1], while the present one investigates the fragmentation of the gel, which constitutes an intermediate stage in the industrial semi-batch process. This series is an expansion of a previous study on mechanical fragmentation of silica gels [2].In a stirred tank, fragmentation of the gel takes place during gelation and essentially influences the properties of the product. Since primary particles in the gel interact strongly with each other but are not rigidly connected, it is assumed that the gel's breakup behavior is similar to that of a highly viscous liquid. The concept of the Weber number [4], in which the surface tension of the liquid counteracts the deformation and, finally, the rupture of a droplet in turbulent flow, was expanded by Arai et al. [3] for highly viscous liquids. The resistance of the liquid against deformation due to surface tension and viscosity was described by a spring and dashpot model. Deformation in a turbulent shear flow was approximated by periodic pressure fluctuations. A relationship between the maximum droplet size x max and the stirring power input e was found for the two extreme cases of very high interfacial tension and very high viscosity. While this again results in the Weber number for viscosity values which are negligible compared to the surface tension, high viscosity combined with negligible surface tension gives the following dependence:(1)This correlation should also be valid for the fragmentation of silica gel. An interfacial tension between the gel and the surrounding liquid is not existent because the gel largely consists of just that liquid, meaning that there is no real interface.It is furthermore probable that the fragment size is defined by an equilibrium between breakage and reaggregation and ...

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“…La théorie a cependant été testée avec un moulin à colloïdes, utilisé dans des conditions de cisaillement simple. Les auteurs ont fait varier la composition des deux phases ainsi que la concentration en tensioactif (Ambruster, 1990 ;Schubert et Ambruster, 1989). Le diamètre moyen des gouttelettes (diamètre de Sauter, d 32 ) a été déterminé et utilisé pour calculer le nombre capillaire critique Ca cr .…”

Section: Application à L'émulsificationunclassified

Génération mécanique des émulsions

Dalmazzone

2000

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Les émulsions sont des systèmes complexes très fréquemment rencontrés dans notre vie quotidienne et dans la plupart des secteurs industriels, dont l'industrie pétrolière. La compréhension des mécanismes de formation des émulsions est essentielle pour assurer la maîtrise de leur fabrication ou de leur traitement. Cet article fait une synthèse des principaux phénomènes qui entrent en jeu lors de la formation d'une émulsion. La rupture des gouttelettes en écoulement laminaire ou turbulent est discutée et des corrélations permettant de prédire le diamètre des gouttelettes formées sont données. On présente également le rôle des tensioactifs ainsi que les échelles de temps caractéristiques des différents processus impliqués. Le cas des émulsions pétrolières obtenues en production est étudié plus particulièrement. Keywords: emulsions, formation, emulsification, droplet size, deformation, breaking, shear, turbulence, crude oil emulsions. Oil & Gas Science and Technology -Rev. IFP, Vol. 55 (2000)

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Prinzipien der Herstellung und Stabilität von Emulsionen

Cited by 31 publications

References 11 publications

Influence of oil‐in‐water emulsion characteristics on initial dynamic flavour release

Influence of oil‐in‐water emulsion characteristics on initial dynamic flavour release

Inorganic Precipitated Silica Gel. Part 2: Fragmentation by Mechanical Energy

Génération mécanique des émulsions

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