Piston-gap homogenizer

In piston-gap homogenization, suspension contained in a cylinder passes a very thin gap with an extremely high velocity. Bubbles of water vapor are produced for... 

Similar to milling processes, high-pressure homogenization uses high shear forces to break down particles in suspension. Typically, piston-gap homogenizers (Fig. 5) are used at pressures up to 2000 bar. 

Fig. 5 The mechanism of particle diminution during piston-gap homogenization. (With permission from Ref...

Fig. 6 Diagram of operation of a piston gap homogenizer. Turbulence and cavitation result in particle size reduction during the homogenization process. From Professor Douglas Goff, Dairy Science and Technology Education, University of Guelph, Canada www.foodsci.uoguelph.ca/dairyedu/ home.html (accessed September 2004).

There are mainly two different principles of high-pressure homogenization used piston-gap principle (e.g. APV Gaulin ) and the interaction chamber principle (e.g. Microfluidics ). Homogenization can be carried out continuously and discontin-uously. 

Finally, compression-extrusion testing involves an extrusion cell commonly used for weakly structured, homogeneous food products. This apparatus consists of a piston that is forced into a cylinder open at one end and containing the product (Figure H2.2.5). Beyond the point of rupture of the food, the compressed material is forced to flow back through the annular space between the piston and the cylinder (Bourne, 1976 Edwards, 1999). The gap between the piston and the cylinder is called the annulus (Bourne, 1982). Variation in the annulus width results in variation in the force required for extrusion (Bourne, 1982). 

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