Which food preservation method involves heating to kill microorganisms?

The method of food preservation that involves heating to kill microorganisms is canning. This process typically involves sealing food in a jar or container and then heating it to a specific temperature for a designated amount of time. The heat destroys harmful bacteria, yeasts, and molds that can spoil food, ensuring that the food remains safe to eat over an extended shelf life.

In canning, different types of food may require different methods and temperatures, depending on their acidity levels. High-acid foods like tomatoes can be processed in a water bath canner, while low-acid foods like vegetables and meats must be pressure canned to achieve the necessary temperatures to eliminate bacteria such as Clostridium botulinum, which can thrive in low-acid environments.

The other methods of food preservation—freezing, dehydration, and refrigeration—do not involve killing microorganisms through heat. Freezing slows down microbial growth by lowering temperatures, but does not kill the microorganisms. Dehydration removes moisture to inhibit microbial growth but doesn't involve heat that actively kills. Refrigeration keeps food at lower temperatures to slow spoilage without necessarily eliminating microorganisms. Therefore, canning is the only method listed that specifically involves heating to ensure food safety through the destruction of microorganisms.