The basics

The basic premise of preserving, otherwise known as “canning,” is that raw or cooked fruits and vegetables are packed into jars with appropriate liquids. They’re then heated to kill off bacteria, which would cause spoilage, and to create a partial vacuum, which produces a tight seal and allows us to keep food for a long time without it becoming contaminated. But that is only the beginning. Acidic foods, such as many fruits, are easily preserved in a boiling water canner, because their acidity inactivates enzymes and potentially poisonous bacteria. Low-acid fruits and vegetables may be pickled or cooked into sauces and chutneys with added acid to achieve the necessary safe acid level, or else they must be preserved at the high heat you can only achieve in a specialized pot called a pressure canner. All this is to say that as a beginner, you are best off following a current, tested recipe and doing some how-to reading. We’re giving you the basics here. When you’re ready to dive in, seek out a recently published canning cookbook (no more than 15 years old) or reputable online sources (those that talk about science and food safety!) for more in-depth info.