Both pasteurization and canning work to kill dangerous microorganisms in food, including bacteria, yeast and mold. Pasteurization boils the food directly, most often milk, whereas the canning method requires the food to be placed in an airtight container before boiling it in either a water bath or pressure canner.
Pasteurization can occur in two ways, depending on the desired shelf life. Regular pasteurization creates a shelf life of two to three weeks and involves heating milk to at least 161.6 degrees Fahrenheit for 15 seconds. Ultra-pasteurization involves heating the food up to 280 degrees Fahrenheit for about two seconds and provides shelf life of around nine months. As far as canning is concerned, the decision to use a water bath canner or a pressure canner depends on the type of food being canned. High-acid foods such as fruit can be canned with a water bath canner. Low-acid foods, such as vegetables, contain a unique organism called the botulinum toxin which requires a pressure canner to kill it.
There is a large debate about whether milk should or should not be pasteurized. Raw milk activists claim that the act of pasteurization kills important vitamins and nutrients in milk. Though it is proven that pasteurization does kill vitamin C in milk, the Center for Disease Control and Prevention claims that milk is not a significant source of vitamin C and that, as a whole, pasteurization does not reduce the nutritional value of milk.