Biology 代写 生物论文代写
Milk can be defined as the lacteal secretion obtained from the mammary glands of mammals by the process called milking. In Kenya, there are many different sources of milk, from cows, goats, sheep and even camels. The most common source of milk, however, is from cows as they are the most common animals in the country. The amount of milk from these cows is enough to satisfy the needs and wants of the country’s population.
As of the year 2008 the estimated cattle population was estimated to be about 3.9 million.
In this experiment, there were 3 different types of cow milk used, Raw cow milk or Unpasteurized cow milk, HTST Pasteurized cow milk and UHT pasteurized cow milk.
Raw cow milk can be defined as the naturally unaltered milk. This milk is not heated above the animal’s highest body temperature which would usually be 38 degrees Celsius. Raw cow milk is therefore not pasteurized, homogenized or frozen, nor has it been altered with additives, chemicals, light or homogenization.
Pasteurization can be defined as the process which slows microbial growth in milk by heating the milk to a specific temperature for a definite length of time, and the cooling it immediately. The process was named after its creator, a French chemist and microbiologist, named Louis Pasteur. The first ever pasteurization test was conducted by Louis Pasteur and Claide Bernard on April 20th 1864. This process was originally created as a way of preventing wine and beer from souring.
This process doesn’t destroy or kill all pathogenic micro-organisms in the milk; it decreases the number of viable pathogens that are likely to cause illness among its consumers. The pasteurization of milk inactivates or kills the organisms that grow rapidly in the milk but does not destroy the organisms that grow slowly or produce spores. Pasteurization of milk typically requires temperatures below boiling since at very high temperatures casein micelles will irreversibly curdle.
Two out of the three types of cow milk I used during this experiment came from some form of pasteurization. These types of pasteurization are: high temperature, short-time pasteurization (HTST) and Ultra high temperature pasteurization (UHT).
Ultra-high temperature pasteurization involves exposing the milk to temperatures exceeding 135 degrees Celsius (275 degrees farenheight) for one or two seconds.
High temperature, short-time pasteurization involves the milk being exposed to heat or temperatures as high as 160 to 165 degrees farenheight (71 to 74 degrees Celsius) for 10 to 20 seconds.
The most effective pasteurization technique is the Ultra high temperature technique as it kills all the pathogens in the milk. Milk that has undergone UHT pasteurization has a longer shelf life and can be kept at room temperature as long as its container is closed.
In Kenya, UHT processing is not as popular as the milk that has undergone HTST pasteurization. This is because the UHT processed milk has a ‘burnt’ taste that does not appeal to the milk consumers in my country.