Hgeocities.com/canningafrica/history.htmlgeocities.com/canningafrica/history.htmlelayedxJd8:OKtext/html8:b.HSun, 17 Sep 2000 19:50:18 GMTcMozilla/4.5 (compatible; HTTrack 3.0x; Windows 98)en, *J8: A Short History of Canning


A Short History of Canning


I. Introduction

Canning, 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.

II. 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.

III. Later Developments

Gradual improvements in machinery and techniques for producing cans resulted in better lining materials, such as lacquers and enamels, and in the development of the sanitary open-top can, in which the top is crimped to the can after filling, producing an airtight seal by means of a rubber gasket. Other developments include the use of cans made of aluminum, very thin steel, and coated and uncoated plastic. Can openers are unnecessary for cans that have a pullable metal tab or ring attached at the top.

Despite the widespread popularity of canned foods, the major limitation of canning is in the quality of the final product. Since food is not a good conductor of heat, excess heat needs to be applied to the container's surface for a period of time to guarantee sufficient heat at the center, or "cold spot," in order to destroy all organisms causing spoilage and disease. This method of preserving causes foods to lose juices, texture, flavor, and nutrients. The retort pouch, developed in the 1970s to alleviate this problem, is a 3-layered laminate with flexible plastic films as the outer and inner layers and aluminium foil in the middle. The pouch, which is approximately 19 mm (0.75 in) thick, is filled and sealed under vacuum. Because the pouch has a large surface-to-volume ratio, heat needs to penetrate less than 10 mm (0.38 in) from the surface to the "cold spot," thereby yielding greatly improved products.

Radappertization is a process of preserving foods in vacuum-sealed cans or 3-layered flexible pouches with sterilizing doses of ionizing radiation. The source of radiation may be gamma rays of cobalt-60 or cesium-137, X rays, or electrons. Because the food is irradiated while frozen (-40 to -18 C or -40 to 0 F), the limitations of conventional heat sterilization are not encountered. As with frozen foods, radappertized foods, prior to vacuum sealing and freezing, must be heated to 70 to 80 C (158 to 176 F) to inactivate viruses and autolytic enzymes that cause loss in texture and flavor. Use of this method on a commercial scale awaits approvals by national health authorities.

IV. Home Canning

Home canning became an important method of preserving food after the American John Landis Mason invented (1858) a practical glass jar and lid, now called the mason jar. The preferred method for home canning is the hot-pack method, in which precooked, hot food and part of the liquid in which it was cooked are placed in a clean, hot mason jar. The mouth of the jar is covered with a metal disk that has a rubber ring seal. A screw-type lid is then partially screwed onto the glass jar. After the jar has been processed in boiling water for the length of time required for the type of food, the screw top is tightened completely. Heat and pressure during processing force most of the air from the jar and minimize the danger of multiplication of disease-causing organisms. Jams and jellies are usually prepared by the open-kettle method. The jam is cooked to the proper consistency, then poured into hot, sterilized jars, which are then sealed. Further heating is not required; the sugar used in preparing jams and jellies acts as a preservative.

See  Botulism; Food Processing and Preservation.

Contributed By:
Edward S. Josephson, Ph.D.
Adjunct Professor, Food Science & Nutrition Research Center, University of Rhode Island.

See an outline for this article.

"Canning," Microsoft Encarta Online Encyclopedia 2000
http://encarta.msn.com 1997-2000 Microsoft Corporation. All rights reserved.


All information Courtesy the "University of Georgia - So easy to Preserve Guide ".

CanninAfrica compiled and maintained

 by Rosalie Acornley Webmaster.