EFFECTS OF PASTEURIZATION AND BOILING ON SOME COMPONENTS OF COW’S MILK

This study was conducted with the objective of investigating the effects of pasteurization and boiling on cow's milk fat, protein and lactose. Forty (40) milk
samples were collected from cows at different parity, number of parity and at the beginning of the lactation season from the morning milking and preserved in a
vaccine carrier (cooler). At the laboratory, each milk sample was divided into three equal parts after using the homogenizer to distribute the fat granules in the
milk. The first, control sample was left fresh without being subjected to heat treatment. The second sample was pasteurized at temperature of 650 C for a
quarter of an hour with a basin pasteurizer and abruptly cooled down. The third sample was boiled using water bath without being exposed to direct flame.
Boiling was done at temperature of 102° C. After cooling, the samples were analyzed to estimate the % fat, protein and lactose (N = 120). The data was
analyzed using analysis of variance. Differences among means were detected by LSD test. The results showed that pasteurized and fresh milk fat was
insignificant, while it was highly significant among boiled, pasteurized and fresh. The mean % fat in fresh milk was 4.68± 0.48, while the fat % in pasteurized milk
was 4.24 ± 0.56. As for boiled milk, the average fat % was 2.68 ± 0.25. Using the LSD test, the results of the study confirmed that boiling the milk led to a large
loss of fat due to heat and it was found that the pasteurization process did not significantly affect the % of fat in cows' milk confirming that boiling decreased
nutritive value of milk, while pasteurization did not significantly affect the milk protein. The % of lactose was not significantly affected. The % lactose in fresh,
pasteurized and boiled milk was 4.8 ± 0.62, 4.2 ± 0.59 and 2.5 ± 0.48%, respectively. There were very significant differences between % fat of boiled and
untreated and pasteurized milk. The study concluded that pasteurization do not change the natural properties of milk and did not negatively affect its nutritional
value. Boiling cow's milk affected the % of lactose, protein and fat in the milk leading to reduction of the nutritional value and changes its properties. The study
concluded that pasteurization of milk for the duration of its preservation period and disposal of pathogenic microorganisms to humans and boiling decreased
nutritive value. The study recommended that milk be pasteurized to retain nutritive value and increase shelf life as well as avoiding infection.