can you kill bacteria with heat ?
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Amber R. Davis
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yes bacteria can be killed with heat
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Heat energy can be applied in three ways: in the form of moist heat (either boiling or autoclaving) or dry heat or by pasteurization. In general, heat kills by denaturing proteins, but membrane damage and enzymatic cleavage of DNA may also be involved. Moist heat sterilizes at a lower temperature than dry heat, because water aids in the disruption of noncovalent bonds (e.g., hydrogen bonds), which hold protein chains together in their secondary and tertiary structures.
Moist heat sterilization, usually autoclaving, is the most frequently used method of sterilization. Because bacterial spores are resistant to boiling (100°C at sea level), they must be exposed to a higher temperature; this cannot be achieved unless the pressure is increased. For this purpose, an autoclave chamber is used in which steam, at a pressure of 15 lb/in2, reaches a temperature of 121°C and is held at that temperature for 15 to 20 minutes. This kills even the highly heat-resistant spores of Clostridium botulinum, the cause of botulism, with a margin of safety. To test the effectiveness of the autoclaving process, spore-forming organisms, such as members of the genus Clostridium, are used. Sterilization by dry heat, on the other hand, requires temperatures in the range of 180°C for 2 hours. This process is used primarily for glassware and is used less frequently than autoclaving. Pasteurization, which is used primarily for milk, consists of heating the milk to 62°C for 30 minutes followed by rapid cooling. (“Flash” pasteurization at 72°C for 15 seconds is often used.) This is sufficient to kill the vegetative cells of the milk-borne pathogens (e.g., Mycobacterium Bovis, Salmonella, Streptococcus, Listeria, and Brucella), but not to sterilize the milk.