Cold-pack canning is a process used to preserve food that is raw or has only been blanched for a few minutes so it will survive in storage for a long time without rotting. The procedure can be used to preserve fruits and vegetables, but also can be used to prepare a jar for pressure canning afterward. The key to successful cold-pack canning is to ensure that all the supplies used, from jars to spoons, are sterile to avoid transmitting into the jar any harmful bacteria that could spoil the food. The basic process is to place the raw or uncooked food into a heated, sterile jar and then possibly cover it with a hot liquid. Once this is done, the jar is placed in boiling water for a period of time before being removed and allowed to cool; at this point, it will be preserved for anywhere from six months to one year or more.
The process of cold-pack canning begins with the preparation of the food to be preserved. For whole fruits or vegetables, this means trimming the food of inedible parts, seeds or pits and cutting large pieces into smaller cubes. Depending on the exact item being canned, it might need to be blanched for a few minutes in boiling water to remove anything undesirable on the surface and to potentially develop flavors. Once the blanching is done, the food is quickly dipped into cold water to stop the process, but it should only be dipped, not left to float in the cold water. Items such as sauces that are mostly liquid do not require these steps.
The food and the cold-pack canning jars and supplies should be ready at the same time to continue the process. The sterile jars, which should still be hot from being sterilized, are filled with the cold food. Hot water, or hot syrup in the case of fruit, is poured into the jar until it reaches 1/2 inch (about 1.25 centimeters) from the top. The lids are then placed on top and partially sealed, meaning that screw tops are turned until tight and then loosened one-quarter of the way back; glass-topped jars should have only one brace secured on the top.
The final step in cold-pack canning is to submerge the jars in boiling water. They need to sit for anywhere from 20 minutes to three hours, depending on the size of the jars and the food inside of them. Once the time has passed, the jars are removed and allowed to cool. The lids are tested when cool to ensure the seal has been made. At this point, the food inside the jars is preserved and can be stored for six months to one year or more.