Click on picture for Operating Instructions
This retort is used for sterilisation of laboratory canned products
History of Canning
Process
The canning process dates back to the late 18th century in France when
the Emperor Napoleon Bonaparte, concerned about keeping his armies fed,
offered a cash prize to whoever could develop a reliable method of food
preservation. Nicholas Appert conceived the idea of preserving food
in bottles, like wine. After 15 years of experimentation, he realized
if food is sufficiently heated and sealed in an airtight container,
it will not spoil. An Englishman, Peter Durand, took the process one
step farther and developed a method of sealing food into unbreakable
tin containers, which was perfected by Bryan Dorkin and John Hall, who
set up the first commercial canning factory in England in 1813. As more
and more of the world was explored, and as provisioning armies took
on greater importance, the demand for canned foods grew. Thomas Kensett,
who emigrated to the United States, established the first U.S. canning
facility for oysters, meats, fruits and vegetables in New York in 1812.
More than 50 years later, Louis Pasteur provided the explanation for
canning's effectiveness when he was able to demonstrate that the growth
of microorganisms is the cause of food spoilage.
The basic principles of canning have not changed dramatically since Nicholas Appert and Peter Durand developed the process. Heat sufficient to destroy microorganisms is applied to foods packed into sealed or "airtight" containers. The canned foods are then heated under steam pressure at temperatures of 240-250° Fahrenheit (116-121° Celsius). The amount of time needed for processing is different for each food, depending on the food's acidity, density and ability to transfer heat. For example, tomatoes require less time than green beans, while corn and pumpkin require far more time.
Processing conditions are chosen to be the minimum needed to ensure that foods are commercially sterile, but retain the greatest flavourand nutrition. Once the cans are sealed and heat processed, the food maintains its high eating quality for more than two years and is safe to eat as long as the container is not damaged in any way.
The sequence of steps in the canning process differs with the product. Fruits and vegetables may be peeled or pitted, and have stems removed prior to canning. Some vegetables receive a heat treatment before they are placed in the can to remove air and improve packing. Acid juices, like orange and tomato, and acid vegetables, such as sauerkraut, can be sterilized before they are placed into containers. Seafood is usually packed after being boned or shelled, with the exception of smaller fish like sardines and anchovies, or even salmon, which have bones that are softened by heating. Meats and fish, like tuna, are usually cooked to soften the flesh before canning, separated from bones, compacted and placed in cans with appropriate liquid.