ReviewProduct engineering of dispersed systems
Introduction
Dispersed systems, e.g. emulsions, foams, suspensions or powders, are commonly found in many branches of industries, ranging from chemical products to cosmetics, pharmaceuticals, food and innovative materials like metal and ceramic foams. Dispersions, in general, are systems with a characteristic structure on a micro-scale, which determines many of their physical properties and thus the quality and functionality of the product; their macroscopic appearance is often homogeneous, though. Stability, rheology, sensory and optical properties or mass transfer kinetics are only some of the properties, which are largely influenced by the micro-structure of a dispersed system. The correlation between a specific property and the micro-structure is called property function (Rumpf, 1967) (Fig. 1). The use of property functions only makes sense, if the main properties are clearly determined by the micro-structure. For dispersed systems this condition is usually fulfilled (Borho, Polke, Wintermantel, Schubert, & Sommer, 1991). Often, the micro-structure can be sufficiently described by a small number of characteristic parameters (e.g. mean values). In this case, properties are independent of the process conditions used to obtain these structural parameters. The structure is determined by the choice of ingredients as well as the preparation process. Changes in the recipe are often limited by functional demands of the final product or they are subject to legal restrictions. Knowledge about the, often cruical, influence of process parameters on structural characteristics is, therefore, indispensible. The desired micro-structure can be obtained by the choice of suitable process conditions, the relation between both is described by the process function (Borho et al., 1991, Polke, 1995). Thus, product engineering of dispersed systems means the design of products with desired properties, taking into account the methods of process or chemical engineering. The micro-structure of the system may be used as linking factor between the process and product properties.
Section snippets
Liquid dispersions: emulsions
Emulsions are dispersions of two or more insoluble liquids, e.g. water and oil, with the dispersed phase distributed in form of small droplets in the continuous phase. From a thermodynamic point of view such systems are unstable. As a consequence, energy input is required in the dispersion step, e.g. mechanical energy for droplet disruption. Afterwards, the dispersed state obtained has to be stabilized over the desired period of storage and usage of the respective product. Both dispersion and
Summary
The task of product engineering is to produce products of a certain quality, i.e. with specific properties. The tools to attain this target are the methods of process engineering. All properties are the result of certain physical, chemical or biological effects in the product, which are determined by the choice of ingredients and processing conditions. The understanding of these basic mechanisms is the key to a purposeful design of product properties. In case of dispersed systems, like
References (46)
- et al.
Preparation and stabilization of simple and multiple emulsions using a microporous glass membrane
Colloids and Surfaces B: Biointerfaces
(1996) - et al.
Effect of dynamic interfacial tension on the emulsification process using microporous, ceramic membranes
Journal of Colloid and Interface Science
(1998) - et al.
Behaviour of monodispersed oil-in-water microsphere formation using microchannel emulsification technique
Priciples of emulsion formation
Chemical Engineering Science
(1993)- Armbruster, H. (1990). Untersuchungen zum kontinuierlichen Emulgierprozeß in Kolloidmühlen unter Berücksichtigung...
- Ax, K., Schubert, H., Briviba, K., Rechkemmer, G., & Tevini, M. (2001). Oil-in-water emulsions as carriers of...
- Behrend, O. (2002). Mechanisches Emulgieren mit Ultraschall. Thesis, Universität Karlsruhe...
- Behrend, O., & Schubert, H. (2001). Investigation of droplet disruption in emulsions due to ultrasound. In Proc. Int....
- et al.
Biological action of carotenoids
FASEB Journal
(1989) - et al.
Produkteigenschaften und Verfahrenstechnik
Chem. Ing. Techn.
(1991)