Final answer:
Heat treatment in pasteurization is brief to eliminate pathogens and reduce spoilage microbes while preserving the food's quality. HTST and UHT are the main pasteurization methods, with HTST preserving milk's sensory qualities and UHT allowing longer storage without refrigeration despite slight flavor changes.
Step-by-step explanation:
Heat treatment in pasteurization is brief because the aim is to kill pathogens and reduce the amount of microbes that cause food spoilage while maintaining the quality of the food. The two common methods used are high-temperature short-time (HTST) pasteurization and ultra-high-temperature (UHT) pasteurization. HTST pasteurization exposes milk to 72 °C for 15 seconds, which effectively reduces bacterial numbers and preserves organoleptic qualities of the milk. On the other hand, UHT pasteurization, which involves heating milk at 138 °C for 2 or more seconds, allows the milk to be stored for longer periods without refrigeration although it may alter the taste and smell due to changes in the milk proteins.
Using these methods of pasteurization ensures that the milk remains safe to consume by eliminating harmful microorganisms such as Campylobacter jejuni, Escherichia coli O157:H7, Mycobacterium tuberculosis and others, without significantly altering the flavor, nutritional value, or freshness of the milk, unlike more prolonged exposure to heat might.