Study of Homogenisation

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  • Topic: Milk, Emulsion, Shear stress
  • Pages : 6 (1772 words )
  • Download(s) : 21
  • Published : November 15, 2010
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This experiment was carried out with the objective to study the effects of homogenisation on the droplet size of the dispersed phase of an emulsion of a two stage homogeniser. The results collected shows that the pressure of the homogenisation process will affect the temperature, height of separation and fat globule distribution of the coconut milk. The process of homogenisation involves pressure forcing the coconut milk through a membrane to make the fat particles small enough to mix together with the watery components of the coconut milk. The samples of coconut milk subjected to higher pressure show a higher temperature with longer time interval, this is due to mechanical friction and shear force in the homogeniser. During this experiment a major precaution which had to be taken was not to allow the feed tank in the homogeniser to run out of liquid as this will cause a malfunction and would spoil the machine.

* To study the effects of homogenisation on the droplet size of the dispersed phase of an emulsion of a two stage homogeniser. Theory
Homogenisation is a method which refers to processing of a solution so that it becomes uniform. It is used in many industrial and scientific applications, even though it is often used specifically to refer to milk, as part of a two stage process which prepares milk for sale. The first stage of processing milk is pasteurisation, it is to sterilise the milk to remove bacteria and stop enzyme reaction. The second stage would be homogenisation, it is to stabilise the milk so that it provides a smoother mouthfeel and flavour. Milk is a solution made up of two different components which do not normally mix well together, in this case it is oil and water. When milk which has not been subjected to the process of homogenisation is allowed to store in the open, the fat globules will slowly rise to the top of the milk. The effect is not desirable for milk consumers at home, they do not want to drink milk which is separated. Therefore the process of homogenisation is crucial so as the two different components in milk will mixed together without being separated out. The process of homogenisation involves the milk being forced through a very fine screen at high pressure. This would then break down the fat particles and merge them together with the watery fraction of the milk, this would result in a uniform liquid which will not separate out as the fat particles are nicely blended together with the water. The product fluid of this process is known as an emulsion, it is define as the combination of two normally not mixable substances together. When milk is subjected to homogenisation, the taste of the final milk product will change. The result of this is due to the fat particles being evenly distributed through the milk. This will cause the milk to taste creamier and gives a smoother texture. But the process of pasteurisation will cause a larger impact on the flavour of dairy products but it is important to prevent food borne illness. There are three factors which contribute to the enhanced stability of the homogenised milk. Firstly, a decrease in the mean diameter of the fat globules in the homogenised milk; it is a factor in Stokes Law. Secondly, a decrease in the size distribution of the fat globules, this will cause the speed of rise to be similar for the majority of the globules such that they will not tend to cluster during creaming. Thirdly, an increase in density of the globules brings them closer to the continuous phase owing to the adsorption of a protein membrane. The process of heat pasteurisation breaks down the cryo-globulin complex, this would then tend to cluster the fat globules causing them to rise. There are some examples of emulsions including oil and vinegar dressing, mayonnaise, and butter. The process of emulsion are mostly irreversible, but when the products of homogenisation are separated this might...
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