Keeping Food: Nine Preservation Techniques

The oldest stop on the path: the earliest known practice of drying food is dated to about 12,000 B.C. among peoples of the modern Asian and Middle Eastern regions. Removing water keeps bacteria, yeasts and molds from growing, which is why raisins, jerky and dried pasta last.

Pickling keeps food in acid, either by fermenting it in brine or by immersing it in vinegar. The atlas dates vinegar pickling to ancient Persia and Mesopotamia around 2400 BCE, and credits brine-fermented pickling to an independent development in China.

Fermentation uses yeasts and bacteria to turn carbohydrates into alcohol or organic acids. Those acids and that alcohol make the food hostile to spoilage organisms, so the same step that creates sauerkraut, kimchi, miso, beer and wine also preserves them.

Curing adds salt to draw moisture out of meat, fish and some vegetables by osmosis, leaving the interior inhospitable to spoilage microorganisms. It is often paired with smoking, drying or nitrates, and gives foods such as prosciutto, bacon, salt cod and gravlax.

Brining is the water-based relative of curing: food is soaked in a salt solution, or treated with coarse salt, to preserve, season and tenderize it. It differs from curing and marination mainly in its shorter duration and its water content.

Smoking exposes food to smoke from burning or smoldering material, most often wood. Hot smoking cooks the food as it flavors it, while cold smoking flavors and historically helped preserve food at temperatures too low to cook it fully.

Confit takes its name from the French confire, to preserve. Food, classically duck or goose, is cooked slowly submerged in its own fat and then stored under a seal of that fat, which excludes air; it is a specialty of southwestern France.

Candying steeps fruit or peel repeatedly in ever stronger hot sugar syrup until sugar replaces the moisture in its cells. The atlas dates the practice to about 1300, and the process can take several days to several months depending on the fruit.

The newest stop: in 1809 the French confectioner and brewer Nicolas Appert observed that food cooked inside a jar did not spoil unless the seal leaked. His method of heating and sealing food became the basis of the modern canning industry.