This document discusses heat sterilization of canned foods. It explains that sterilization uses high temperatures to kill bacterial spores, while pasteurization only kills some microorganisms. The key principles are that sterilization in an autoclave above 100°C is needed to kill the heat-resistant spores of Bacillus and Clostridium bacteria. The autoclave process heats food in sealed containers to temperatures over 110°C for a set time period to ensure all spores are inactivated before the container is cooled. Common foods suitable for canning include cooked meats, sausages, and ready-to-eat dishes containing meat.

1. Heat sterilization of canned food
ABDUL VAHID M
B110167CH
DEPT. OF CHEMICAL ENGG.

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