Milk pasteurization is a process that involves heating milk to a specific temperature and holding it there for a set period of time to destroy any harmful bacteria that may be present in the milk. This process was developed by Louis Pasteur in the late 19th century and has since become a standard practice in the dairy industry to ensure the safety and quality of milk.
There are several different methods of milk pasteurization, including high-temperature short-time (HTST) pasteurization, ultra-high temperature (UHT) pasteurization, and low-temperature long-time (LTLT) pasteurization. The most common method used today is HTST pasteurization.
HTST pasteurization involves heating the milk to a temperature of 161°F (71.7°C) for 15-20 seconds, followed by rapid cooling to below 50°F (10°C). The process is typically done using a plate heat exchanger, which consists of a series of plates with narrow channels through which the milk flows. The plates are heated and cooled by a heating and cooling medium, such as hot water and chilled water.
The milk is first preheated to around 145-149°F (63-65°C) before entering the plate heat exchanger, where it is heated to the pasteurization temperature of 161°F (71.7°C) and held there for 15-20 seconds. After pasteurization, the milk is rapidly cooled to below 50°F (10°C) to prevent any further bacterial growth.
UHT pasteurization is a more intensive method of pasteurization that involves heating the milk to a temperature of 280°F (138°C) for 2-6 seconds. This process effectively sterilizes the milk, eliminating all bacteria and spores, and allows the milk to be stored at room temperature for several months.
LTLT pasteurization involves heating the milk to a temperature of 145°F (63°C) for 30 minutes, followed by rapid cooling to below 50°F (10°C). This method is less commonly used today, as it is slower and less efficient than HTST pasteurization.
Overall, milk pasteurization is a critical step in ensuring the safety and quality of milk products. By destroying harmful bacteria and other pathogens, pasteurization helps to prevent foodborne illnesses and extends the shelf life of milk and milk products.