2. Canning….??
method of preserving food from spoilage by storing it in
containers that are hermetically sealed and then
sterilized by heat.
The process was invented after prolonged research by
Nicolas Appert of France in 1809.
The heat killed the microorganisms in the food, and the
sealing kept other microorganisms from entering the jar.
3. How sterilization differ from
Pasteurization..??
Pasteurization is a heat treatment food preservation
method that kills a part of the microorganisms present in
the food. usually a liquid is heated to a specific
temperature for a predefined time period followed by
immediately cooling step (E.g. 63-66 °C for 30 minutes or
71°C for 15 seconds).
Sterilization is another form of thermal processing
technique which uses comparatively high temperatures,
Since the bacterial spores are far more heat resistant than
the vegetative cells, the main objective of this technique
is to destroy their spores.
4. Principles of heat sterilization
Heat treatment of food products must be intensive enough to
inactivate/kill the most heat resistant bacterial microorganisms,
which are the spores of Bacillus and Clostridium .
In practice, the meat products filled in sealed containers are exposed
to temperatures above 100°C in pressure cookers. Temperatures
above 100°C, usually ranging from 110-121°C depending on the type
of product, must be reached inside the product.
If spores are not completely inactivated in canned goods, vegetative
microorganisms will grow from the spores as soon as conditions are
favourable again. The surviving microorganisms can either spoil
preserved meat products or produce toxins which cause food
poisoning of consumers.
5. Principles of heat sterilization
Amongst the two groups of spore producing microorganisms
Clostridium is more heat resistant than Bacillus. Temperatures of
110°C will kill most Bacillus spores within a short time. In the case of
Clostridium temperatures of up to 121°C are needed to kill the spores
within a relatively short time.
The above sterilization temperatures are needed for short-term
inactivation (within a few seconds) of spores of Bacillus or
Clostridium.
These spores can also be killed at slightly lower temperatures, but
longer heat treatment periods must be applied in such cases to arrive
at the same summary effect of heat treatment.
6. Processes and equipment
Process
The sterilization process in the canned product can be subdivided
into three phases .
By means of a heating medium (water or steam) the product
temperature is increased from ambient to the required
sterilization temperature (phase 1 = heating phase).
This temperature is maintained for a defined time (phase 2 =
holding phasing).
In (phase 3 = cooling phase) the temperature in the can is
decreased by introduction of cold water into the autoclave.
7. Autoclaves or retorts
In order to reach temperatures above 100°C (“sterilization”), the thermal treatment has
to be performed under pressure in pressure cookers, also called autoclaves or retorts.
Large horizontal autoclave
Double purpose equipment
8. Autoclave
it is a pressurized device designed to heat aqueous solutions above their
boiling point at normal atmospheric pressure to achieve sterilization.
Auto self
Clavis self -locking device
Boiling point of water is directly proportional to the pressure when the
volume is constant.
When pressure is increased in a closed vessel the temperature
increases proportionately.
ie.for about 15 pounds of pressure per square inch (Psi) ---
the temperature rises to 121oC.
This pressure and temperature is kept constant for 20 minutes during
autoclaving.
It is sufficient to kill all the vegetative forms and spores of the organism.
9. Sterilization in autoclave
There are two methods
Wet sterilization
By coagulating and denaturing enzymes and structural protein.
Resistant spores generally requires 121 °C for 15-30 minutes
Dry sterilization
By destructive oxidation of essential cell constituents.
Resistant spores requires a temperature of about 160 °C for
60 minutes.
10. Types of containers for thermally treated preserves
Containers for heat-preserved food must be hermetically sealed and
airtight to avoid recontamination.
Most of the thermally preserved products are in metal containers
(cans),. Others are packed in glass jars or plastic or
aluminum/plastic laminated pouches.
11. Meat products suitable for canning
following groups of meat products are frequently
manufactured as canned products:
cooked hams or pork shoulders
sausages with brine of the frankfurter type
meat preparations such as corned beef, chopped pork
ready-to-eat dishes with meat ingredients such as beef
in gravy, chicken with rice
soups with meat ingredients such as chicken soup,
oxtail soup