Meat Spoilage due to microorganism

1. SPOILAGE OF MEAT

2. CONTENT
Infection
1.Endogenous
2. Exogenous infection
Factors affecting the growth of Meat Spoilage
1.Tempearture
2.Moisture and Osmotic Pressure
3.pH
4.Oxidation reduction potential
5.Atmospehere
6.High pressure
Prophylaxis

3. Infection
The organisms which spoil meat may gain access through
infection of the living animal (endogenous disease) or by
contamination of the meat post-mortem (exogenous disease).
Endogenous (Before death)
Consumption of meat from infected animal
Example: Anthrax, bovine tuberculosis and brucellosis.
Causal agents: Bacillus anthracis, Mycobacterium tuberculosis
and Brucella spp
20–30 per cent of all cattle in Britain were affected by
tuberculosis towards the end of 19th century.

4. Exogenous infection
Exogenous
Infection of meat after processing (After death of animal)
Parasitic worms, bacteria, fungi infects the meat after death and
it leads to spoilage of meat. Where there is proper meat
inspection to eliminate infected carcasses from distribution, the
predominant mode of meat deterioration by invading organisms
will be by exogenous infection.
1. Bacteraemia
2. Sources and nature of external contamination

5. Bacteraemia
There is an equilibrium between invasion of the tissues
and removal of the invading organisms such that the
tissues of healthy animals are normally free from bacteria.
If an infected knife is used, or organisms are inadvertently
introduced from the skin whilst the main blood vessels are
being severed, bleeding can itself lead to bacteraemia and
to the infection of the animal’s tissues.
Meat can be contaminated by bacteria that persist on
powered tools (e.g. air-driven knives) used in carcass
dressing

6. Sourcesand natureof externalcontamination
External contamination of the meat is a continuing possibility
from the moment of bleeding until consumption.In the abattoir
itself there are a large number of potential sources of infection
by micro-organisms.
These include
 The hide,
 Soil adhering
 The contents of the gastrointestinal tract (if inadvertently
released during dressing operations)
 Airborne contamination
 Aqueous sources (the water used for washing the carcass, or for
cleaning the floors)
 The instruments used in dressing(knives, saws, cleavers and
hooks),
 Various vessels and receptacles,
 Personnel

7. Typical microbial counts in sources of
microbial contamination in an abattoir

8. Some characteristics of
bacterial meat poisoning

9. Symptom of Spoilage

10. Factors affecting the growth of
Meat Spoilage
 Temperature
 Moisture
 pH
 Oxidation-reduction potential
 Atmosphere
 High Pressure

11. Temperature
The most important single factor governing microbial growth is
temperature.
Broadly, the higher the temperature the greater is the rate of
growth. Many meat micro-organisms will grow to some extent
at all temperatures from below 0 °C to above 65°C, but, for a
given organism, vigorous growth occurs in a more limited
temperature range.
Spoilage organisms in three categories
Psychrophiles : temperature between –2 °C and 7 °C,
Mesophiles : 10 °C - 40°C
Thermophiles : 43 to 66 °C

12. The effect of temperature on the rate
of growth of various bacteria

13. Moisture and osmotic
pressure
After temperature, the availability of moisture is perhaps the
most important requirement for microbial growth on meat,
although some types of bacteria may remain dormant for
lengthy periods at low moisture levels, and spores resist
destruction by dry heat more than by moist heat.
The availability of moisture is complementary to that of osmotic
pressure, which is a function of the concentration of soluble,
dialyzable substances (salts, carbohydrates, etc.) in the aqueous
medium.
High solute concentrations tend to inhibit growth
Molds and yeasts tolerate higher osmotic pressures than
bacteria
Bacteria growing from an aw : 1.0 -0.75
Yeasts and molds growing slowly at an aw of 0.62

14. Theeffectofsurfacemoistureandtemperature
onmicrobialgrowthonlambcuts

15. pH
pH of meat will be determined by the amount of
lactic acid produced from glycogen during
anaerobic glycolysis and this will be curtailed if
glycogen is depleted by fatigue, inanition or fear in
the animal before slaughter.
Most bacteria grow optimally at about pH 7
Not well below pH 4 or above pH 9

16. Optimal pH values and salt concentration
for ham spoilage organisms

17. Oxidation–reduction
potential
Immediately after death, whilst temperature and pH are
still high, it would be expected that the dangers of
proliferation of, and spoilage by, anaerobes would be
great. That such does not generally occur appears to be
due to the level of the oxidation–reduction potential which
usually does not fall for some time.
The presence of nitrate in cured meats probably exerts an
indirect antibacterial effect through raising the Eh of the
system.

18. Atmosphere
A major grouping of micro-organisms can be made on the basis
of the oxygen tension which they need or can be made to
tolerate – aerobes, anaerobes and facultative.
The exposed surfaces of fresh meat at chill temperatures would
normally support the growth of aerobes such as members of the
genera Achromobacter and Pseudomonas.

19. High Pressure
The degree of pressure inactivation is affected by
the type of micro-organism, the pressure applied,
the duration and temperature of the applied
process and the pH of the medium. The
inactivation of micro-organisms by high pressure
appears to be due to intracellular damage.
There is considerable variation in susceptibility to
pressure between the types of micro-organism
found in meat.

20. Prophylaxis
1. Hygiene
2. Biological Control
3. Antibiotics
4. Ionising radiation