Canning means, the preservation of food in
permanent, hermetically sealed containers
(of metal, glass, thermostable plastic, or a
multi-layered flexible pouch) through
agency of heat.
Heating is the principle factor to destroy the
microorganisms and the permanent sealing
is to prevent re-infection.
Nicholas Appert invented the
canning process in 1809.
Emperor Napoleon Bonaparte
of France was the first to use it.
century- canned food
used mainly by military.
CoNtAINers for CANNed
1-) Capable of being hermetically sealed to prevent
entry of microorganisms.
2-) Impermeable to liquids and gases, including
water vapour .
3-) Maintain the state of biological stability (i.e,
commercial sterility) that was induced by the thermal
process alone or in combination with other chemical
and physical processes.
4-) Physically protect the contents against damage
during transportation, storage and distribution.
(a) Metal- Steel & Aluminium: most frequent used
package for canning food.
Tinplate, tin-free steel, and nickel-plated steel coated
with a very thin film of tin are the materials used to
manufacture metal food cans.
Cans used in the food industry are coated on the inside
with two general kinds of organic coatings-
acid-resistant: used primarily for fruit.
sulfur-resistant: used primarily for Meat products.
(c) Glass containers and metal closures
The canning process itself consists of several stages:
1.Cleaning- passing the raw food through tanks of water or under high-pressure
2.Preparing the raw food material- vegetable or other products are cut, peeled,
cored, sliced, graded, soaked, pureed, and so on
3.Blanching- immersion in hot water or steam
4.Filling the containers- usually under a vacuum;
5.Closing and sealing the container- done automatically by machines; cans
are filled with solid contents and, in many cases, with an accompanying liquid
(often brine or syrup) in order to replace as much of the air in the can as possible
6.Sterilizing the canned products- they are heated at temperatures high
enough and for a long enough time to destroy all microorganisms (bacteria,
molds, yeasts) that might still be present in the food contents. The heating is
done in high-pressure steam kettles, or cookers, usually using temperatures
around 240° F (116° C).
7.Labeling and warehousing the finished goods- cans are then cooled in cold
water or air, after which they are labeled.
Two meThods of processing
Water-bath processing- Canning jars filled with food
and with special canning lids are secured completely
and immersed in boiling water for an amount of time
specified in the canning recipe.
After processing, as the jars cool,
a vacuum seal is formed.
It can only heat the food to the
temperature of boiling water.
A pressure canner is
a heavy-duty piece
of equipment with a
vent, a pressure
gauge and screw
clamps. It is capable
of heating the food in
the jars to hotter
than the temperature
of boiling water.
Botulism caused by Clostridium botulinum produce
toxin in a sealed jar of food.
Home-canned vegetables are the most common cause
of botulism outbreaks in the United States.
From 1996 to 2008, there were 116 outbreaks of
foodborne botulism reported to CDC.
These outbreaks often occur because-
home canners did not follow canning instructions
did not use pressure cookers/canners
ignored signs of food spoilage
were unaware of the risk of botulism from improperly