Methods include preventing the growth of bacteria, fungi and other microorganisms, and slowing down the rancidity of fat due to oxidation.
Common preservation methods include drying, freezing, vacuum bagging, canning, radiation and adding preservatives. In addition, there are some methods, which not only prevent corrosion, but also enhance flavor, such as water immersion, sugar pickling, smoking and so on.
The oldest method is air drying. Without water, bacteria live very slowly. Sometimes smoke is added during the drying process. Although it is only smoked for a short time, antibacterial ingredients are added to the food during the smoking process. Meat or fruit is sometimes preserved with sugar or salt, such as beef jerky.
Flooding is to soak food with strong salt water or vinegar. Most microorganisms can't live in an environment that is too salty or too acidic.
Bottles are very common in Europe and America. They are used to hold vegetables and fruits. Sterilize the bottles and cans first, then put them in, and boil the bottles and contents together for disinfection. After cooking, bottles and jars need to be sealed. In the past, wax was used, but in modern times, most bottle caps with rubber inner rings were used.
Different foods have different natural antibacterial abilities. Sour fruits like strawberries don't need to be added, just cook them gently. Tomatoes need to be cooked for a long time, and other acidic things should be added. Many vegetables must be canned under pressure.
In the 1950 s, the American magazine Popular Mechanics put forward the idea of food irradiation. But until now, the consequences of food radiation are not clear, so it is not very common. Potatoes, strawberries and meat are often irradiated in areas where cold storage facilities are not common. The United States did not approve the radiation of meat and poultry until 2002 to prevent Escherichia coli and Salmonella. In the United States and many European countries, spices are often irradiated because there is no other good way.