This document discusses commercial sterilization and heat treatment processes for preserving meat at high temperatures. It covers factors that influence sterilization like pH levels and container size. Pathogens like Clostridium botulinum that can grow in low-acid foods are described. Equipment for thermal treatment includes retorts, which use steam or hot water to achieve sterilizing temperatures above 100°C. Proper containers, thermal processing times and cooling are required to eliminate microbes and allow shelf-stable storage. Common meat products suitable for canning include cooked ham, sausages and ready-to-eat dishes.

1. Preservation of meat
at high temperatures

2. • More severe thermal food process
• Long -term shelf stability
• Traditionally used for canned food
• now for a broad range of products
What is commercial sterilization?

3. General Concepts
Factors accounts for commercial sterilization:
• pH or acidity of products
• heating and cooling characteristics of the product
in the container
•Other factors:
• the size of the container
• the types of heating and cooling media utilized

4. Commercial sterilization
• High-acid foods:
• thermal resistance of microbial spores associated
with economic spoilage
• Low-acid foods:
• thermal resistance of spores of microbial
pathogens.
• Medium acidity:
• similar to high-acid foods

5. •Foods with pH greater than 4.5 will support
the growth of Clostridium botulinum
• which produces an extremely potent exotoxin, and
lead to extreme human health hazard.
•The potency of the toxin is sufficient to create
65% fatality in humans who ingest the toxin.

6. • Clostridium botulinum:
• anaerobic, spore-forming
microorganism
• a sealed container provides an
ideal environment for the growth
of Clostridium botulinum,
• and the production of toxin;
• gas production;
• cause visible swelling of the
container.

7. Heat treatment of processed
meat products
• 􀂾 Enhancement of desirable texture, flavour and colour,
in order to make meat products more palatable and
appetizing for
consumption.
• 􀂾 Reduction of microbial content thus achieving the
necessary
- preservation effects for an extended shelf life
(storability) of
the products and
- food safety effects by eliminating potential food
poisoning agents.
serves two main purposes:

8. CHARACTERISTICS OF HEAT-
TREATED PRESERVED MEAT AND
MEAT PRODUCTS
• The prolonged shelf-life of heat-
treated meat and meat products is
achieved through reducing growth
of,
• or inactivating, micro-organisms by a
thermal process.

9. • The principal steps of heat preservation method
are to:
• Place the product in a container (can, glass jar,
pouches of synthetic material or laminate with
aluminium)
• Which is hermetically sealed after filling and
• is impermeable to any external substances; and
• Submit the hermetically sealed product to
thermal treatment
• with a defined temperature and time combination.

10. EQUIPMENT FOR THERMAL
TREATMENT
• Thermal or heat treatment is done by
submerging the products
• in cooking vats or pressure cookers which contain
hot water or steam or a mixture of both.
• It can be performed under pressure in pressure
cookers (retorts, autoclaves)
• in order to reach temperatures above 100°C
(“sterilization”).

11. • Sterilization is the most important and efficient
type of heat treatment,
• since foods free from viable micro-organisms
can be obtained and
• most of these products can then be stored
without refrigeration

12. • In contrast, temperatures up to 100°C can be
achieved in simple cooking vats
(“pasteurization”).
• A certain amount of micro-organisms resist
this moderate heat treatment and
• the resulting pasteurized products must
consequently be stored under controlled
temperatures

13. Retorts
• The most important phase of sterile canning
process is retorting
• The retort operation serves two purposes:
• Products are subjected to a high temperature
for sufficient duration to destroy all microbes
• those that affect the health of the consumer, as well
as
• resistant organisms that could cause spoilage under
normal storage conditions
• Products are cooked so they can be eaten
directly as they come from the can.

14. Retort cooker
1. body,
2. lid,
3. counterbalance,
4. nuts,
5. heater,
6. vent,
7. relief valve,
8. pressure gauge,
9. water supply valve 1
10. steam supply valve.

15. • A retort is a steel tank in which metal
crates or baskets containing the cans are
placed for cooking and subsequent cooling.
• It is fitted with a cover or door, which can
be closed to provide a seal to hold the
cooking or cooling pressure.

16. • In simple retort cookers (autoclaves)
• pressure is generated either
• by a direct steam injection,
• by heating water up to temperatures over 100° C or
• by combined steam and water heating.
• The retort must be fitted with a thermometer, a
pressure gauge and a relief valve
• Modern autoclaves may also have revolving
drums, speeding up the heating of the products.

17. • After thermal treatment the product must be
chilled as quickly as possible, in order to avoid
overcooking.
• Hence, this operation is done within the cooker
by introducing cold water.
• The contact of cold water with steam causes the
latter to condense with a rapid pressure drop in
the retort.

18. Types of retorts…
• Non-agitating retorts
• Continuous agitating
retorts
• Hydrostatic retorts.

19. Non –agitating retorts..
• Also referred to as “still or stationary” retorts
• Most commonly used for canning meat
• These retorts are closed-pressure vessels that operate in
excess of atmospheric pressure
• and use pure steam or superheated water as the
heating medium for cooking.
• The steam comes from an external source ,such as
a steam boiler or generator.

20. • Non –agitating retorts function on a batch
basis
• that is, the retort must be loaded
• then closed, and the entire batch cooked
• before the second batch of product can be put in.
• Non –agitating retorts can be vertical or
horizontal.
• They are constructed for various maximum
pressures,
• But standard construction used in the meat
industry is 15 psi maximum operating pressure.

21. Horizontal retorts.
• Vary in size and shape. (round,
square)
• With doors at one or both ends.
• They can be as large so as to move
carts or trucks ,in and out directly
from the canning floor.
• Efficiency could be increased
by having doors at both ends,
• thereby allowing uncooked
products to enter at one point
and
• cooked products to be
discharged at another.

22. Vertical retorts
• Are more efficient than
horizontal ones with respect to
the number of cans they will
hold per unit of retort volume.
• Vertical retorts also occupy
less floor space for a given
capacity
• but more mechanical handling
of the baskets or crates is
required.

23. Continuous Agitating retorts..
• As the name implies, the cans are
agitated while in the retort.
• This results in a shorter processing
schedule
• Made possible by a faster rate of heat
penetration into the meat.

24. Hydrostatic retort..
• In this retort, steam pressure
is maintained by water
pressure.
• These retorts or cookers are
• made up of water and steam
chambers referred to as “legs”
• the temperature of the water in
the water-chamber varies from
60° to 250°F
• that of steam in the steam
chamber is controlled by pressure
produced by the water chamber.

25. • Steam temperatures between 240° and
265°F are generally used.
• Operation of a hydrostatic cooker is as
follows:
Cans are conveyed through the machine by
means of carriers connected to chains.
The cans enter a water chamber where the
temperature is about 180°F.
This is the down-travelling water chamber
where the product temperature begins to
increase.

26. • As the can moves down through this chamber, they
encounter hotter water.
• In the lower part of the chamber, the water
temperature reaches 225° to 245°F.
• Then, near the water seal area next to the steam
chamber,
• the water temperature increasingly approaches that of
steam.
• In the steam chamber, the cans are exposed to a
temperature between 240° to 265°F.

27. • Advantages :
• Saving in floor space
• Reduction in operating cost
• Because steam and water costs are
lower due to regenerative heating and
cooling
• Greater capacity for high-volume
operation.
• Disadvantage :
• Large initial capital investment required.
• Limitation on sizes that can be cooked in
a given unit

28. Closing
• Before closing the cans,
• large cuts of meat are pressed to ensure correct
can fit, and
• to eliminate air pockets.
• Pasteurized canned meats are closed on a
vacuum closing machine with 18 to 25 in. of
machine vacuum.

29. CONTAINERS FOR THERMALLY
TREATED PRESERVES
• Containers for heat-preserved food must
be airtight in order to avoid
recontamination by environmental
microflora.
• Currently, most of the thermally preserved
products are in
• metal containers (cans),
• others are packed in glass jars or
• plastic or
• aluminium/plastic laminated pouches.

30. • Metal containers are cans (tins) produced from
tinplate or tin-free steel.
• They are usually cylindrical.
• Other shapes such as rectangular or pear-shaped
cans are also used.
• Tinplate consists of steel plate, plated with tin on
both sides.
• Tin-free steel plates have other protective coatings
such as
• chromium,
• aluminium, or
• nickel,
• which are generally even thinner than the tin layers of
the tinplate.

31. • For smaller and easy-to-open cans aluminium
is frequently used.
• Aluminium cans are deep-drawn,
• i.e. the body and the bottom end are formed out of
one piece and
• only the top end is seamed on after the filling
operation.

32. • The advantages of aluminium cans are
• low weight,
• Resistance to corrosion,
• Good thermal conductivity and
• Recyclability ,
• but these cans cannot be soldered or welded.
• They are less rigid and more expensive than steel
plate.

33. • Glass jars are used less often for meat
products because of their fragility.
• They consist of a glass body, and a metal lid.
• The seaming panel of the metal lid has a
lining of synthetic material.
• Glass lids are fitted by means of a rubber ring.

34. • Containers made either of synthetic material or
laminates of aluminium foil with synthetic material are
of growing importance in thermal preservation.
• Heat-resistant plastic pouches, which are closed by
clip,
• are usually made of polyester (PETP)
• and used for ready-to-eat dishes.

35. MEAT PRODUCTS SUITABLE FOR
CANNING
• Basically all meat products which require heat
treatment to prepare them for consumption
are also suitable for heat preservation.
• Only meat products which do not receive any
form of heat treatment before being
consumed,
• such as dried meat, raw hams or dry sausages, are
naturally not suitable for canning

36. Canned meat products…
• Cooked ham
• Sausages with brine of the frankfurter type
Meat preparations such as corned beef,
chopped pork, etc.
• Ready-to-eat dishes with meat ingredients
such as beef in gravy, chicken with rice, etc.
• Soups with meat ingredients such as chicken
soup, etc.