The healthy inner flesh of meats have been reported
to contain few or no organisms,.
Although they have been found in lymph nodes, bone
marrow, & even flesh.
Staphylococci, streptococci, Clostridium, & Salmonella
have been isolated from the lymph nodes of red meat
So normal slaughtering practices would remove the
lymph nodes from edible parts.
Approved “humane” methods of slaughter-
mechanical, chemical, electrical- have little effect of
But each method is followed by sticking & bleeding,
which can introduce contamination.
4. • The important contamination comes from external
sources during bleeding, handling & processing.
Sources of contamination may be:-
• Knives, cloths, air, & clothing of workers.
• During handling of meat, boxes, containers, air, & other
• During bleeding, skinning & cutting main source of
micro-organisms are the exterior of the animal & intestinal
• In the market, knives, saws, cleavers, slicers, grinders,
chopping blocks, scales & containers.
• In Home refrigerators previously used containers used to
• Growth of organisms on surface, touching the meats &
on the meat themselves increases their numbers.
Meat is the most perishable food.
Preservation of meats are more difficult than other foods.
So the preservation of meats is done by combination of
Keeping organisms away from meat, during slaughtering
& handling, permits easier preservation by any method.
Water spraying to the animal before slaughter has been
preferred to remove as much as gross dirt.
Meat & meat products are preserved by following eight
7. 1. Use of heat
The canning of meat is very specialized technique – in that the
procedure varies with the meat product to be preserved.
Chemical added to meats, such as, spices, salts, or nitrates in
curing processes, also affect the heat processing, & make it
Nitrates in meat helps to kill spores of anaerobic bacteria by
heat & inhibit germination of surviving spores.
Commercially canned meats can be divided into 2 categories:-
1. Meats that are heat processed to make the can contents sterile
or “commercially sterile” as for canned meats for shelf storage in
retail stores .
This meat group is also referred as “ shelf stable canned meats”.
The Processing temperature of this canned cured meats is 98 C.
Size of the container is less than 1 lb.
8. 2. Meats that are heated enough to kill part of the spoilage micro-
organisms but must be kept refrigerated to prevent spoil.
This meat group is called as non-shelf stable or “ keep refrigerated”
They are packed in containers upto 22 lb.
Processed at temperatures of about 65 C.
HEAT MAY ALSO BE APPLIED IN OTHER WAYS THEN CANNING:-
Hot water can be used for treatment of meat surfaces to lengthen
the keeping time of meat..
But this may lessen the nutrients & damage color.
Hot water reduces the numbers of organisms & helps preservation.
Heat applied during the smoking of meats & its products helps to
reduce microbial numbers
Cooked sausages such as frankfurters & liver sausage, also be
spiced but should be kept refrigerated.
9. 2. Use of low temperatures
More meat is preserved by the use of low temperatures, 1st chilling &
then by freezing method.
Modern packing house methods involve chilling meat immediately &
rapidly to temperature near freezing
Chilling storage at only slightly above the freezing point.
The more prompt & rapid this cooling, cause less growth of
Storage temperature vary from -1.4 to 2.2 C, with the lower
Time limit of chilling is depending upon microbial load & vary
according to animal:-
For beef, is about 30 days , for pork, lamb & mutton is 1-2 weeks, for
a veal, needs short period.
Uncooked sausage must be preserved by refrigeration.
Storage time can be increased by 2.5 to 3 ppm ozone in the
Ozone is an active oxidizing agent, that may give an oxidized or
tallowy flavor to fats.
10. 2. FREEZING
Freezing often is used to preserve meats:-
during shipment over long distances,
for holding until times of shortage,
quantities of meat now are frozen in home freezers.
The preservation of frozen meats is increasingly effective as
the storage temperature drops from -12.2 to -28.9 C.
The freezing process kills about half the bacteria..
And numbers decrease slowly during storage.
The low temperature bacteria that grow on meat during
That is from species of Pseudomonas, Alcaligenes,
Micrococcus, Lactobacillus, Flavobaterium , & can resume
growth during the thawing of meat after this is done.
11. 3. Use of irradiation
Irradiation with UV rays has been in conjunction with
chilling storage to lengthen the keeping time.
The rays serve:-
to reduce numbers of organisms in the air &
to inhibit or kill them on the surface of the meat.
Irradiation has been used in the rapid aging of meats,
that are ‘hung’ at higher than the usual chilling
temperatures to reduce the growth of organisms on the
Gamma irradiation of meats still is limited & in the
Because it cause undesirable changes in flavor & color.
12. 4. Preservation by drying
Meat for drying should be of good bacteriological quality to
avoid undesirable flavor.
Meat products, such as dry sausages & dry cervelats are
preserved by their low moisture content & dryness.
Dried beef made mostly from cured, smoked beef hams,
growth of organisms may takes place before processing..
And may develop in the ‘pickle’ during curing..
But Numbers of organisms are reduced by the smoking &
Drying may be by vaccum, in trays.
Drying pork involves a short nitrate-nitrite cure before drying &
addition of lecithin as an oxidant & stablizer…
The final product keeps without refrigeration.
Freeze drying processed products include.. Meat patties, meat
13. 5. Use of preservatives
Use of preservatives is combined with curing & smoking in order to
The curing of meats is limited to beef & pork.
The curing agents permitted are:-
sodium chloride, sugar, & nitrate are commonly used, vinegar is
Functions of the agents are:-
Sodium chloride- used as a preservative & flavoring agent. Its
main purpose is to lower Aw.
Sugar adds flavor & serves as an energy source for nitrate-
reducing bacteria in the curing solution. Sucrose is chiefly used ,
glucose used as a subsituted.
Nitrate used as a color fixative & has some bacteriostatic effect in
Sodium chloride attributed most preservative effects of the
Salts, Sugars, & meat protein combine to lower the Aw value of
the cured meats.
14. There are 4 methods for introducing curing agents into meat:-
1. The dry cure-
dry ingredients are rubbed into the meat.
2. The pickle cure-
the meats are immersed into a solution of the ingredients.
3. The injection cure-
a concentrated solution of the ingredients is injected by
needle into arteries of the meat.
4. The direct addition method-
the curing agents are added directly to finely ground meats.
The curing temperature usually is about 2.2 to 3.3 C.
And the time of the cure varies with the method used.
The older method of curing in the pickle require several months..
Where as the newer ‘quick cure’ in which pickling solution is
pumped into the meat, greatly shortens the time.
15. 6. Smoking:-
Smoking has two main purposes:-
1. To add desired flavors.
2. To aid in preservation.
Preservative substances added to the meat, together with the
action of the heat during smoking, have a germicidal effect.
Drying of the meat, together with chemicals from the smoke,
inhibits microbial growth during storage.
Spices and condiments added to meat products to add their
effect to other preservative factors.
For example – bologna, polish, & frankfurter & other sausages
owe their keeping quality to the combined effect of spicing,
curing , smoking, cooking, & refrigerating.
16. 8. Antibiotics
Antibiotics can be used successfully in meats to prolong
storage life at chilling or high temperature.
The most often recommended antibiotics are:-
chlortetracycline & chloramphenicol.
The antibiotics may be applied to meats in various methods-
1. The antibiotic may be fed to the animal over a long period.
2. It may be fed to more intensively for a short period before
3. It may be infused into the carcass or its part of it.
4. It may be applied to the surface of pieces of meat or mixed
with continued meat.
Antibiotic injection before slaughter might be employed to
prolong the keeping time of carcasses at atmospheric
temperature before they reach the refrigerator.
The storage life of meats could be lengthened by the means
Raw meat is subjected to change by its own enzymes & by
microbial action & its fat may be oxidized chemically.
Factors that influence the invasion include:-
a. The load of gut of the animal- more the load, greater the
invasion of tissues.
b. The physiological condition of the animal immediately
before slaughter- if the animal is excited, feverish bacteria
is more likely to be enter the tissues.
c. The method of killing & bleeding- the better sanitary the
bleeding, better would be the keeping quality of meat.
d. The rate of cooling- rapid cooling will reduce the rate of
invasion of tissues
18. Factors that influence the growth of microorganisms to cause
spoilage are as..
1. The kind and amount of contamination with microorganisms &
the spread of these organisms in the meat.
2. The physical properties of meat-
The amount of exposed surface of the flesh influence on the
rate of spoilage.
3. The chemical properties of meat-
The moisture content of the meat determine organisms to
4. Availability of oxygen-
Aerobic conditions at the surface of meat are favorable to
yeasts, molds & aerobic bacteria.
Low-temperature organisms can grow on stored temperature
of meat i.e. not far above freezing.
19. GENERAL TYPES OF SPOILAGE OF MEAT
SPOILAGE UNDER AEROBIC CONDITIONS
1. Surface slime-
which may be caused by species Pseudomonas, Leuconostoc, Bacillus,
Alkaligenes, Micrococcus etc.
Temperature & availability of moisture, influence the kind of organisms causing
2. Changes in color of meat pigments-
The production of oxidizing agents causes change in red color of meat to
shades of green, brown & gray, by bacteria species of Lactobacillus.
Red color of meat called as “bloom.”
Leuconostoc causes greening of sausages.
3. Changes in fats-
The oxidation of unsaturated fats in meats takes place chemically in air & may
be catalyzed by light & copper.
Lipolytic bacteria may cause lipolysis off flavor due to aldehyde & acids.
Lipolytic species viz., Pseudomonas & Achromobacter.
20. 4. Phosphorescence-
Uncommon defect caused by luminous bacteria.
Ex. Photobacterium growing on the surface of meat.
5. Various surface color due to pigmented bacteria-
Red spot caused by Serratia marcescens.
Blue colour caused by Pseudomonas syncyanea.
Yellow pigments produced by the sps of Micrococcus or Flavobacterium.
Greenish blue to brownish black spots on stored beef caused by
Purple “stamping ink” discoloration of surface fat caused by yellow pigmented
cocci and rods.
6. Off odors and off tastes-
“Taints” or undesirable tastes & odors, appear in meat due to growth of bacteria
on the surface often are evident before other signs of spoilage.
Souring is term applied to almost any defect, that gives a sour odor may be due
to volatile acid.
“Cold storage flavor” or taint is an indefinite term for a stale flavour.
Actinomycetes may cause musty or earthy flavour.
21. Aerobic growth of yeast on meat:
Under Aerobic conditions, yeast grow on the surface of meats,
causing Sliminess, lipolysis, off odors, & tastes, and discolorations.
Aerobic growth of molds on meat:
Stickiness: Incipient growth of molds makes the surface of the
meat sticky to the touch.
Whiskers: White fuzzy growth can be caused by a number of
molds including sps. Thamnidium, Mucor, Rhizopus and others.
Black spot: Cladosporium herbarum.
White spot: Sporotrichum carnis, Geotrichum.
Green patches: Penicillium expansum, Penicillium asperulum,
Decomposition of Fats: Many molds have lipases and hence
cause hydrolysis of fats.
Off odour and off tastes: Molds give a musty flavour to meat in
the vicinity of their growth. Sometimes this defect is given a name
called “thamnidium taint”.
23. SPOILAGE UNDER ANAEROBIC
Facultative and anaerobeic bacteria are able to grow within the
meat under anaerobic conditions to cause spoilage.
The terminology used in connection with this spoilage is:-
The term implies a sour odor.
This could be caused by formic, acetic, byutric, propionic and
higher fatty acids or other organic acid like lactic.
Vacuum packed meats, especially those in gastight wrappers,
commonly support the growth of lactic acid bacteria.
Acid and gas formation accompany the action of the “butyric”
Clostridium sps and the coliform bacteria on carbohydrates.
Souring can result from-
a. Action of meat own enzymes during ripening
b. Anaerobic production of fatty acids or lactic acid during ripening.
c. Proteolysis without putrefacation, caused by anaerobes & called
as “Stinking sour fermentation”.
24. 2. Putrefaction:-
True putrefaction is the anaerobic decomposition of protein with the
production of foul smelling compounds.
It usually is caused by species of Clostridium.
But facultative bacteria may cause putrefaction in its production, by
species of Pseudomonas putrfaciens, putrificum etc, chiefly in the
genera Pseudomonas and Alcaligenes.
Gas formation accompanies putrefaction by clostridia, the gases
being hydrogen & CO2.
Trimethyl amine in fish and isovalenic acid in butter are described
as putrid odors.
This word is implied to any off-taste, off-odor.
The term ‘bone taint’ is implied to souring or putrefaction.
True putrefiers require temperature above those of refrigerator.
25. SPOILAGE OF DIFFERENT KINDS OF MEATS
1. Spoilage of Fresh meats:
Extended refrigeration may have the growth of Pseudomonas,
Acinetobacter, Moraxella and causes spoilage of fresh meat.
Lactic acid bacteria chiefly of the genera Lactobacillus, Leuconostoc,
Streptococcus, Brevibacterium and Pediococcus are present in most
meats, fresh or cured and can grow even at refrigerator temperatures.
2. Fresh beef: Putrefaction, Souring, Phosphorescence, discolorations.
(Pseudomonas & Micrococci)
3. Hamburger: Bacillus, Clostridium, Escherichia coli, Enterobacter,
Proteus, Pseudomonas, Alcaligenes, Lactobacillus, Leuconostoc,
Streptococcus, Micrococcus and Sarcina.
4. Fresh pork sausage: Lactobacilli, Leuconostocs, Microbacterium,
5. Spoilage of cured meats: Sodium nitrite lactic acid bacteria in
sausages like thuringer & leads to lactic acid fermentation.
26. 6. Dried Beef or Beef Hams:
Sour – by variety of bacteria
Red – due to Halobacterium salinarum or red Bacillus sps.
Blue – Pseudomonas syncyanea, Penicillum Spinulosum (purplish),
Greening of sausage is due to the production of peroxides (Ex: H2O2) by
heterofermentative sps of Lactobacillus and Leuconostoc or other
catalase negative bacteria.
Acid forming Micrococci (Micrococcus candidus) and Bacillus may grow
in liver sausage and bologna.
8. Bacon: Aspergillus, Alternaria, Monilia, Oidium, Fusarium, Mucor,
Rhizopus, Botrytis and Penicillium.
Souring caused by Alcaligenes, Bacillus, Pseudomonas, Lactobacillus,
Proteus, Serratia, Bacterium, Micrococcus, Clostridum.
10. Refrigerated packaged meats:
Pseudomonas, Acinetobacter and Moraxella
27. 11. Curing solutions (or) pickles:
Multiuse brines generally spoiled by putrefactive
bacteria. Ex: Vibrio, Alcaligenes or Spirillum.
Souring can be caused by Lactobacillus and
Micrococcus and slime by Leuconostoc or
28. SPOILAGE IS ALSO INFLUENCED BY
Not only air but temperature has an important influence
on the type of spoilage to be expected in meat.
When meat is held at temp. near 0°C, microbial growth
is limited to molds, yeasts, & bacteria able to grow at low
This include:- sliminess, discoloration and spots of
growth on the surface.
Many bacteria can cause souring. Such as
Pseudomonas, Lactobacillus, Leuconostoc,