Let us know about churning and centrifugation. We use many milk products; cream, butter, cheese etc. Ever wondered how these milk products are made? We have seen at home or in pictures, a pot full of milk being agitated with a plunger like device, usually a cylindrical stick to separate cream from milk. This process is carried out to separate cream from milk which later may be used for making butter or solid cream. This process of agitation of milk is termed as churning.
The process of churning is defined as the agitation of cream to form butter. Earlier, only manual techniques were available for this process. For example: using the traditional churner as shown in Fig. 1, where a pot full or milk cream was fitted with a plunger, which was then rotated to create agitation. Another hand powered device is shown in Fig. 2 where two and fro motion is established instead of rotational.
The process of churning is not very efficient as it takes a lot of time and labour. So, for larger quantities, the process of centrifugation is carried out. In churning, the plunger is rotated and the container containing the mixture remains constant, whereas in a centrifuge, the container is made to rotate, such that centrifugal force directly acts on the components.
Centrifugation is the process that uses centrifugal force for the separation of two liquids in a mixture. In this process, denser component of the mixture migrates away from the axis and lighter component migrates towards the axis.The process of centrifugation is carried out in a centrifuge, as shown in Fig 7.
Let us understand this process with the example of milk, as the tubes containing the milk are rotated, the heavier milk is pulled outward against the wall, whereas, the lighter cream is collected in the middle. Both the components are then collected separately.
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