Does hot or cold temperatures kill bacteria?

Bacteria can be killed by both high and low temperatures. High temperatures, typically above 60°C (140°F), can denature proteins and disrupt the structure and function of bacteria, causing them to die. This is the principle behind pasteurization, a process used to kill harmful bacteria in milk and other beverages by heating them to high temperatures for a short period.

On the other hand, extremely cold temperatures, such as those below freezing (0°C or 32°F), can also be lethal to bacteria. When temperatures drop below freezing, the water inside bacterial cells forms ice crystals, which can damage cellular components and disrupt metabolic processes. This can eventually lead to the death of the bacteria. However, it's worth noting that some bacteria, known as psychrophilic or psychrotrophic bacteria, are well-adapted to cold environments and can survive and even grow at low temperatures.

In general, the effectiveness of temperature in killing bacteria depends on several factors, including the specific type of bacteria, the temperature range, and the duration of exposure. Different bacteria have varying degrees of heat and cold tolerance, and the time required to kill them can vary. Therefore, specific temperature ranges and exposure times are often determined based on the target bacteria and the desired level of disinfection or sterilization.