Pasteurization is a process in which the temperature of the raw milk is raised to a certain level for some time, and then immediately cooled to lower degrees to destroy most of the pathogenic bacteria. This is done to improve the keeping quality, taste and flavour of the milk. Undesirable taints of the milk are also removed by this process.
Pasteurization is the process of exposing the milk to a controlled temperature for a specific time with the object of destroying all the pathogenic and souring bacteria, and cooling the milk immediately to a temperature low enough to retard the growth of the surviving bacteria.
It has been observed that a time-temperature combination of not less than 145o F and not more than 150oF maintained for 30 minutes or a temperate of not less than 161°F maintained for 15 seconds, followed by a rapid cooling to a temperature of not more than 50°F is sufficient to kill most of the common disease producing bacteria.
It can easily be argued that when milk is boiled at homes why the milk is also being pasteurized in the dairies. Pasteurization of milk increases the cost of market milk. In order to understand and justification of pasteurization of milk in the dairies one should know the basic differences between pasteurization and boiling.
Boiling of milk would mean raising the temperature of milk to its boiling point under atmospheric temperature and pressure. The boiling point of milk is l00.17°C which is decidedly higher than the usual temperature adopted in holding method of HTST pasteurization process. Boiling of milk certainly destroys all the pathogenic organisms and makes it safe for human consumption, but there is no need for heating the milk for such a higher temperature when the same objective is fulfilled by pasteurization process.
Extra heating of milk will amount to loss of heat energy and nutritive value of milk which otherwise could be avoided. Also, in boiling process, there is no cooling involved hence the growth of those microorganisms which survive heat treatment is not retarded and, therefore, boiled milk has lower keeping quality than the properly pasteurized milk.
Boiling of milk is uneconomical and practically impossible in the dairies where large volumes of milk is handled every day. For individual household consumer boiling of milk prior to consumption is certainly a useful practice. The common belief amongst the older generation that drinking of raw milk as it is obtained from the udder of animals is the best way of its consumption has to be contradicted on scientific grounds. This concept is rather more important in the present days where organized dairies collect milk from various sources and the hygienic practices in handling of milk are still far from satisfactory. The health of a large population will be at stake if milk is distributed without any resources to heating.