Types of Food Preservation

Food preservation has existed in many forms for thousands of years as a means to prevent spoilage and extend the life of different types of food. The three main preservation techniques are canning, preserving, and pickling—all of which are easy to master at home. Though the three methods have many similarities, they’re used for different things.

Invented about 200 years ago, canning can be used to preserve fruits, vegetables, and meats. It works by isolating food in sealed containers—glass jars, despite what “canning” suggests—and heating the food to a temperature high enough to deactivate its natural enzymes and kill any harmful microbes. The container’s seal prevents airborne bacteria from recontaminating the food and allows it to be stored at room temperature without risk of spoilage.

Unlike sugar preserving or pickling, canning generally doesn’t significantly alter the taste of foods through the use of large amounts of sweeteners or vinegars. All canned food, though, is exposed to heat for prolonged periods and is essentially cooked—and therefore tastes different than its fresh counterparts.

Canning is also a catch-all term for the act of sealing food in containers and processing them using heat. It’s also sometimes used as a synonym for heat processing, so it often appears in sugar preserve or pickle recipes that call for sealing and heat-processing the jars.

Sugar preserving requires cooking fruits (and occasionally vegetables) with large amounts of sugar to prevent the growth of bacteria. The sugar removes moisture from the plant cells, creating an inhospitable environment for microbes. When sugar and fruits or vegetables are cooked together, they form a uniform mass called a gel with a consistency that ranges from runny and spreadable to congealed and chewy (for more information, see How to Make Sugar Preserves). The gel is poured into sterilized jars and either sealed, heat-processed, and stored at room temperature, or simply refrigerated.

Pickling works by submerging fruits, vegetables, or meats either in an acidic solution called brine or in oil in order to extend their life and change their flavor. There are three main types of pickles you can make, described briefly here (for more information, see How to Pickle).

To make acidified pickles—the simplest form of pickles—vinegar or citrus juice is mixed with salt, water, sugar, or spices to create a brine, which is poured over the food being pickled. The submerged food is then refrigerated or sealed in jars, heat-processed, and stored at room temperature. The acid in the brine inhibits the growth of harmful microbes, and the food absorbs the flavor of the brine. Bread-and-butter pickles are an example of acidified pickles.

In place of vinegar as a preservative, fermented pickles rely on naturally occurring acids that develop when foods are left packed in salt or a salt solution at room temperature for anywhere from a few days to several months. Full- and half-sour pickles, sauerkraut, and kimchi are all made this way.

The salt prevents the growth of harmful bacteria while encouraging the growth of beneficial ones already present in the food. These bacteria produce acids that preserve and flavor the pickles. Depending on their salt content and storage method, fermented pickles can be refrigerated, kept at room temperature, or sealed and heat-processed in jars. Heat-processing fermented pickles, however, kills the active bacteria cultures that offer many health benefits.

Unlike acidified or fermented pickles, oil pickles don’t undergo a chemical process. Instead, oil is poured over food to deprive it of oxygen. Oil pickling is common in oil-rich countries such as Italy, as well as in tropical regions where—before the age of refrigeration—it was difficult to control the temperature of stored foods. Because most oils are mild or neutral-tasting, cooks often infuse them with flavors such as garlic, herbs, or chile peppers. Mangoes, mushrooms, cauliflower, and olives are frequently pickled in oil.