Homogenizers


Homogenizers are the most efficient laboratory tool for particle and droplet size reduction. They reduce materials into uniform-sized molecules through high-speed, high pressure maceration or cutting. Although the properties of the resulting material depend on the homogenizer and the original material, homogenizers generally are capable of reducing particles to sizes of .2 to 2 microns and blending them to create a stable dispersion or emulsion for further processing.

In general, higher pressure during processing results in smaller sized particles. Many homogenizers can also be used for shredding, wetting, dissolving, emulsification, extraction, precipitation, cell rupture, and similar processes. Although homogenizers can be used with many different types of materials, they work best with materials that have high moisture, fat, or fiber content. Some of their most common uses include industrial processing, pharmaceutical and cosmetic preparations, food service, and bioresearch and laboratory testing.

Types of Homogenizer

There are a number of different types of homogenizer. The three most common are rotor/stator generators (or colloid mills), high pressure (or piston pump) models, and sonic disruptors.

Rotor/stator homogenizers are the most common type. They are capable of shearing large quantities of material in a long shaft that has angled knives at the bottom. The knives shred the material, which is then drawn up into a stator tip and ejected from small holes in the side of the stator to be sheared again and again.

This type of homogenizer tends to be quick and efficient and is capable of handling plant and animals tissues and other more solid materials for cell disruption and similar techniques. In general, materials are completely homogenized within 20 to 60 seconds. Foaming and aerosols can be a problem with certain types of materials.

High pressure homogenizers are usually used with liquids and similar materials and this is the method most often used when homogenizing milk. They work by forcing the material through small tubes or valves with a piston pump under very high pressures (up to 1,500 bar / 21,750 psi with continuous full-scale operation.)

Sonic disruptors, or sonicators reduce break up particles with the disruptors, which generate intense ultrasonic waves ranging from about 18 to 50 kHz. Ultrasonic waves of this frequency are inaudible to the human ear, but capable of exerting pressures of more than 500 atmospheres and temperatures of up to 5,000 degrees C. The waves are amplified by a probe or horn into an intense beam the produces the cutting or shearing effect on particles through a process called cavitation.

Under the right conditions, the pressure waves cause microscopic bubbles to form, which grow to a certain point and then collapse violently. The implosion generates a shock wave that breaks cell membranes, reduces particle size, and even breaks covalent bonds. Sonic disruptors can produce free radicals, which are capable of disrupting certain kinds of samples.

By Kerry Given           


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