What did people use to preserve their food when they didn't have refrigerators?

Multiple methods of preserving foods have been used throughout history. Among the earliest were drying, smoking, and salting. Each of these methods forced liquid out of a food, making a poor environment for bacterial growth. Smoking and salting further added antibacterial substances to kill off bacteria.

Areas with extreme cold made use of natural "refrigeration" and freezing to preserve foods. Even in areas without year-round freezing, there were methods of cold-management, including preservation of winter...

Multiple methods of preserving foods have been used throughout history. Among the earliest were drying, smoking, and salting. Each of these methods forced liquid out of a food, making a poor environment for bacterial growth. Smoking and salting further added antibacterial substances to kill off bacteria.

Areas with extreme cold made use of natural "refrigeration" and freezing to preserve foods. Even in areas without year-round freezing, there were methods of cold-management, including preservation of winter ice in ice-houses, and the use of cold artesian springs or deep-drilled cold cases to keep foods cold enough to slow bacterial growth.

After these, intentional forms of fermentation were used. These methods of preservation, which included the making of cheeses, wines, and beers, as well as complex products like soy sauce, allowed favored safe and useful bacteria to settle in food, forcing out hostile, harmful bacteria. These friendly bacteria in many cases also made foods more easily accessible to human digestion. One example of this would be the conversion of milk to products such as yogurt, sour cream, and cheese, breaking down natural milk sugars that many people can't digest as adults and replacing them with less difficult byproducts.

Later developments included preserving methods such as simmering in sugar syrups, complete cooking and encasing in hard fats, and eventually early forms of jarring and canning. Only in the 1800s and 1900s did preservation become a scientific and industrial process, with foods canned, jarred, and eventually frozen and dried on a mass basis.