Compare and contrast the different uses of heat to reduce microbial contamination, including their relative efficacy.

Question

What will be an ideal response?

Answer 1

Autoclaving, the use of super-heated steam, is a rapid, effective means of sterilization, both because the temperature achieved (121°C) inactivates every infectious agent except prions, and the steam is penetrating. Dry heat sterilization is equally effective but requires higher temperatures for longer periods of time (up to 170°C and/or 2 hours). Boiling is effective in killing vegetative cells of all microbes but is not effective on bacterial endospores and some cysts. Ultra-high-temperature sterilization is a highly effective process for sterilizing liquids. Standard pasteurization procedures effectively kill the mesophilic microbes responsible for disease and most spoilage, but does not remove endospores, nor thermoduric and hyperthermophilic microbes. This lower level of microbial reduction is sufficient in the short term since it is the mesophiles that are most troublesome in terms of disease and spoilage. The primary effect of these methods is denaturation proteins, thus inhibiting metabolism. Higher temperature methods cause additional damage, including to cell membranes, cell walls, and DNA.

Low temperature heating that produces desiccation is effective in inhibiting the metabolism of most microbes by reducing the water content of the materials. It is not effective against some fungi, and does not destroy endospores.