Centrifugation

The technique of separating substances under the influence of centrifugal force is termed as centrifugation. Particles get separated from the solution on the basis of their density, shape, size, medium viscosity, and the speed of the rotor of the centrifuge. A centrifuge is a machine which rotates around a fixed axis, in which the force acts perpendicularly to the axis of the spin, i.e., in an outward direction. Gravity and the centrifugal force generated in the centrifuge form the basis for the separation of different fractions. This chapter covers the principle of centrifugation, types of centrifuge, their instrumentation, types of centrifugation process, and practical application of centrifugation process applied to milk. The design and working of various types of centrifuges like desktop clinical centrifuges, high-speed centrifuges, microcentrifuge, vacuum centrifuge/concentrators, and ultracentrifuges have been discussed. Three types, namely ultracentrifuge, high-speed and low-speed centrifuge, have been compared. Types of rotors used in centrifuges like fixed angle rotors, vertical tube rotors, and swinging-bucket rotors have also been discussed. Preparative centrifugation methods like differential gradient centrifugation, density gradient centrifugation which included rate-zonal centrifugation and isopycnic centrifugation, and analytical centrifugation methods have been explained.