Describe the method of pasteurization for the preservation of milk.

Pasteurization is a heat treatment process named after Louis Pasteur that preserves milk by heating it to specific temperatures for controlled time periods to kill harmful pathogenic bacteria while retaining nutritional value, flavor, and overall quality better than boiling. The most common method is High Temperature Short Time (HTST) pasteurization, where milk is rapidly heated to 72°C (161°F) and held at that temperature for 15 seconds before being quickly cooled to 4°C or below. This process destroys disease-causing microorganisms including Mycobacterium tuberculosis, Salmonella, E. coli, Listeria, and other pathogens that can contaminate raw milk, while preserving most vitamins, proteins, and calcium content.

Alternative pasteurization methods include Low Temperature Long Time (LTLT) pasteurization, where milk is heated to 63°C (145°F) for 30 minutes, commonly used for smaller batches and specialty products, and Ultra-High Temperature (UHT) processing, where milk is heated to 135-150°C for 1-2 seconds, producing shelf-stable milk that can be stored unrefrigerated for months in sealed containers. The pasteurization process involves heating raw milk in specialized equipment with precise temperature controls, holding at the target temperature, rapidly cooling to inhibit any surviving bacteria from multiplying, and packaging in sterile containers. Pasteurized milk must still be refrigerated to maintain freshness and safety, though it has a significantly longer shelf life (typically 7-14 days) than raw milk. This process revolutionized public health by virtually eliminating milk-borne diseases like tuberculosis, typhoid fever, and brucellosis in regions with pasteurization infrastructure.