There are two ways of canning food at home: the boiling-water method and the pressure-canning method. Both methods work essentially the same way. The ingredients are prepared and loaded into jars with special lids that allow steam to escape. The jars are heated and as they cool, the food contracts and creates an airtight seal that preserves the contents for up to a year.
The boiling-water method is an easy way to get started because the equipment investment is minimal, says Vinton. It’s suitable for acidic foods, like fruit jams and jellies, salsas, tomatoes, and vegetables that have been made more acidic with the addition of vinegar, lemon juice, or citric acid.
Pressure canning is for low-acid foods, which includes most vegetables and meats. These need to be heated to a higher temperature in a special pressure-canning appliance to keep bacteria at bay.