I. Introduction
Canning is the process of preserving food by heating and sealing it in airtight containers. The process was invented (1809) by Nicolas Appert,
a French confectioner. In the Appert process, the food was cooked in open kettles and placed in glass jars, which were sealed by corks wired in place. The jars were then heated by submersion in boiling water. Commercial canning was introduced into the United States in 1821 by
the William Underwood Company of Boston.

Early Canning Methods
In 1810 an English inventor, Peter Durand, patented the idea of using tin- plated cans. Later, calcium chloride was added to the water used to sterilize the food sealed in the cans, to raise the temperature of the water above 100° C (212° F). Although the food was heated faster,
the increased internal pressure often burst the cans. In 1874 the closed- vessel process, in which the cans were heated by steam under pressure, was invented; the pressure of the steam compensated for pressure that developed in the can, largely eliminating the bursting of cans.