CANNING (CAN BE TRIED @ HOME)

Canning has been in vogue since 1825 and has provided a way to store foods for extremely long periods of time. In canning, food is boiled in the can to kill all the bacteria and the can is sealed (either before or while the food is boiling) to prevent any new bacteria from getting in. Since the food in the can is completely sterile, it does not spoil even for years. Once you open the can, bacteria enter and begin their action on the food. This is the reason you see the label on all sorts of canned food products that you have to "refrigerate the contents after opening" (it means that the contents are sterile until you open the container).

We generally think of "cans" as being metal, but any sealable container can serve as a can. Glass jars, aluminium foil, plastic pouches and boxes can be boiled and sealed. For example, milk in a tetra pak that one can store on the shelf is "canned" milk. The milk inside the box is made sterile (using Ultra High Temperature (UHT) pasteurization) and sealed inside the box, so it does not spoil even at room temperature.

The reason, why refrigeration or freezing is preferred to canning, is that during boiling of food in the can it generally changes its taste and texture (as well as its nutritional content).