The open-kettle or cooked-in-the-kettle and the cold-pack or cooked-in-the-can are the two methods of canning now commonly used.

Description of the Open Kettle Method

The open-kettle method is so called because the food to be canned is completely cooked in a kettle before it is poured into the jar. This method involves more risk than the cold-pack, because, unless the jar, the cover, the rubber, and all the utensils that come in contact with the food have been thoroughly sterilized by being boiled for several minutes before the jars are filled, and unless the work is carefully done, there is always the risk that the canned food will be infected and that it may spoil after the jar has been sealed. For some products, however, such as thick preserves and conserves, for which more intense heat than that of boiling water is needed, the open-kettle method must still be used. Many persons, too, prefer the open-kettle method for canning strawberries and tomatoes. It is not advisable to use it for non-acid vegetables or meats.

Description of the Cold-Pack Method

In the cold-pack method the uncooked or partly cooked food is packed in the jars, covered with water, sirup, or ice; and both the jar and its contents are heated simultaneously by boiling water or steam. This method is recommended for most fruits and all vegetables and meats, because it is not only a safer, easier way of canning most foods than the old open-kettle method, but also because the product retains much of its natural flavor and color and more of its nutritive value.