Microorganism in fresh meat and

poultry
https://www.slideshare.net/HiwrHastear/food-
spoilage-60301573
 What is Meat?
• Meat is animal flesh that is
eaten as food. Humans are
omnivorous , and have hunted
and killed animals for meat
since prehistoric times.

• The advent of civilization

allowed the domestication of
animals such as chickens, sheep,
pigs and cattle, and eventually
their use in meat production on
an industrial scale.
• Meat is mainly composed of water and protein , and is usually eaten
together with other food.

• It is edible raw, but is normally eaten after it has been cooked and
seasoned or processed in a variety of ways (e.g., curing or smoking).

• Unprocessed meat will spoil within hours or days.

• Spoilage is caused by the practically unavoidable infection and
subsequent decomposition of meat by bacteria and fungi, which are
born by the animal itself, by the people handling the meat, and by
their implements.
Meat as a Food Source
• Complete protein source
• Excellent source of iron
• Fat, makes the product juicy, tender, and adds flavor
• Fresh meat is a highly nutritious substrate with water activity of
about 0.99, meaning that it is suitable for the growth of most
microorganisms.
• Raw meat in general contains bacteria, including pathogenic and
spoilage ones. As warm-blooded animals naturally carry bacteria
such as Salmonella spp. in their intestines, raw meat may be
contaminated with bacteria during the slaughtering process such as
evisceration and dressing procedures.
• In addition, the equipment and tools used in the processes, the
hands and clothing of personnel as well as the environment may
also contaminate the meat with bacteria.

Raw meat should be cooked thoroughly before consumption.

• Meat has potential to carry foodborne pathogens that can
cause illness and lead to food safety problems.

• These pathogenic bacteria are able to invade our bodies or

produce toxins to cause illness.

• They cannot be seen or smelled on the meat, but can

generally be killed by normal cooking conditions (i.e.
cooking to a core temperature of at least 75°C
instantaneously or other effective time/ temperature
combinations).
 The most heavily colonized areas of the animal that usually
contaminates meat are the skin (fleece) and gastrointestinal tract.

 The animal may carry a mixed microbial population of Micrococci,

Staphylococci, Pseudomonads, Yasts and moulds as well as organisms
derived from sources such as soil, faeces , water.
Types of Meat
Meat can be broadly classified as "red" or "white" depending on
the concentration of myoglobin in muscle fibre.

Red Meat White Meat

• When myoglobin is exposed to oxygen , reddish oxymyoglobin
develops, making myoglobin-rich meat appear red. The redness of
meat depends on species, animal age, and fibre type.

• Nutrients zinc, iron, thiamine and riboflavin (in addition to

vitamins B12 and B6) appear in much greater abundance in red
meat.
Composition of Meat
 Most animal muscle is roughly 75% water, 20% protein, and 5% fat
and carbohydrates.

 Muscle is made up of muscle fibers which are long, thin,

multinucleated cells bound together in bundles.

 Each cell is packed with filaments made of two proteins: Actin

and Myosin.
Poultry Meat

• Poultry meat like meat of other animals is also susceptible to contamination by

various sources.

• Contamination of skin and lining of the body cavity take place during various
processing operations.

• The organisms of great importance in poultry are Salmonella spp. and

Campylobacter jejuni. Several Gram negative psychrotropic bacteria viz.,
Pseudomonas, Acenitobacter and Flavobacterium have also been isolated from
poultry carasses.

• Ground turkey also may carry fecal streptococci.

• It is important to freeze the poultry fast in order to keep it in good condition for
several months. Freezing further reduces the number of microorganisms in the
poultry meat provided the temperature is maintained quite low (-18 ° C or below).
 Microbial Growth in Meat

 High water activity and abundant nutrients make

meat an excellent medium to support microbial growth.

 The carbohydrate content of muscle has a particularly

important bearing on its microbiology.
 Microbiology of Primary Processing
 The tissues of a live animal are protected against microbial infection by a
combination of physical barriers and the activity of the immune system.

 Microbial numbers detected in aseptically sampled tissues are usually less

than 10 cfu/ Kg but this number could be more for infected animals.

 Visual inspection before and after slaughter to identify and exclude unfit
meat is the general rule, although it will only detect conditions which give
some macroscopic pathological sign.

 The most heavily colonized areas of the animal that usually contaminates
meat are the skin (fleece) and gastrointestinal tract.

 The animal hide may carry a mixed microbial population of micrococci,

staphylococci, pseudomonads, yeasts and moulds as well as organisms
derived from sources such as soil, faeces, water.
 Microbiology of Primary Processing
 Meat gets more microbial contamination during the processing
when the head, feet, hides, excess fat, viscera and offal are
separated from the bones and muscular tissues.
Skinning spreads contamination from the hide to the freshly
exposed surface of the meat carcass.
 Washing the animal prior to slaughter can reduce microbial
numbers.
 The viscera contain large numbers of micro-organisms,
including potential pathogens. Puncture or leakage from the
anus or oesophagus during removal increases contamination.
 After dressing, carcasses are washed to remove surface
microflora, although bactericidal washing treatments such as hot
water, chlorinated water or dilute lactic acid have been shown to
reduce the surface microflora.
 After dressing the carcass (meat) is cooled to chill
temperatures which may cause some reduction in numbers.
 Psychrotrophic organisms predominate subsequently as the
meat is held constantly at chill temperatures.
 Spoilage of Meat
 Aerobic storage of chilled meats, either unwrapped or covered with an
oxygen permeable film, produces a high redox potential at the meat
surface suitable for the growth of psychrotrophic aerobes.

 Non-fermentative gram-negative bacteria (rods) grow most rapidly

under these conditions.

Major component of spoilage microflora

Pseudomonas (P. fragi, P. lundensis and P. fluorescens),
Acinetobacter and Psychrobacter

Minor component of spoilage microflora

Psychrotrophic Enterobacteriaceae (Serratia liquefaciens and
Enterobacter agglomerans), lactic acid bacteria and the Gram-
positive Brochothrix thermosphacta.
 Indication of Spoilage of Meat
Indication of spoilage in fresh meat is the production of off
odours (107 cfu/ cm2). At this point, bacteria uses amino
acids as substrates.
 Microbial metabolism produces a complex mixture of
volatile esters, alcohols, ketones and sulfur-containing
compounds which collectively give the off odours.

 Enterobacteriaceae, lactic acid bacteria and Brochothrix

thermosphacta use glucose as substrate to produce buttery
or cheesy odour associated with production of 2,3-
butanedione, acetoin (3-hydroxy-2-butanone), 3-methyl-
butanol and 2-methylpropanol.
Indication of Spoilage of Meat
Predominant role of pseudomonads:

Pseudomonads begin to develop a sweet or fruity

odour (production of esters by Pseudomonas
species degrading glucose and amino acids and
by esterification of acids and alcohols.

As glucose becomes exhausted, the meat

develops a rotten odour because Pseudomonas
species and some Acinetobacter and Moraxella
species solely use the amino acid pool,
producing volatile sulfur compounds such as
methane thiol, dimethyl sulfide and dimethyl
disulfide.
Vacuum and modified-atmosphere packing alter
bacterial growth

changes the meat microflora

Accumulation of CO2 and the absence of

oxygen restrict the growth of pseudomonads.

Meat microflora is dominated by Gram-

positives, lactic acid bacteria(Lactobacillus).
Characteristics of some Gram-negative Bacteira
associated with meat
Health Benefits and Dangers of Eating Red
Meat
Nutritional benefits from eating red meat:
• Red meat is high in iron and the heme iron in red meat is easily
absorbed by the body which prevents several diseases like anemia.
• Red meat also supplies vitamin B12, which keeps nerve and red
blood cells healthy, and zinc, which keeps the immune system
working properly.
• Red meat provides protein, which helps build bones and muscles.

• Beef is one of the most nutrient-rich foods.

Dangers of Eating Red Meat

 Red meats are high in saturated fat, which raises blood Cholesterol.
High levels of low-density lipoprotein (LDL cholesterol increase the
risk of heart disease (Atherosclerosis).

 Saturated fat has been linked to develop cancers of the colon and
breast.
• Meat that can be considered red meat most commonly comes from
the flesh of big mammals like mutton and beef.
• White meat or light meat is the contrast to red meat, and it is also
referred to as light meat. White meat can also refer to lighter
colored meat that comes from poultry.

• It is commonly agreed that white meat consists of meats like rabbit

and chicken.
• White meat is best known as meat that is lean, especially in
comparison with red meat. The big point about white meat is that
its fat content is less in comparison with red meat.
 Major component of spoilage microflora

Pseudomonas (P. fragi, P. lundensis and P. fluorescens), Acinetobacter and

Psychrobacter

Minor component of spoilage microflora

Psychrotrophic Enterobacteriaceae (Serratia liquefaciens and Enterobacter
agglomerans), lactic acid bacteria and the Gram-positive Brochothrix
thermosphacta.
Salmonella
• Salmonella typhimurium is found in pigs, cattle and
chickens.
• Salmonella enteritidis is found in egg-producing hens.
Salmonella is a gram-negative
Temperature range 5-460C.
Heat treatment of meat to around 700C will
kill Salmonella.
Salmonella is also capable of surviving in
frozen meat or chilled meat .
 They can grow in foods with a water activity down to 0.94 (8% salt)
but can survive in products with low water activity.
 Salmonella is capable of multiplying both under aerobic and
anaerobic conditions as well as in modified atmosphere with 20%
CO2.
 Salmonella grows in foods with pH above 4 .
Sources of Salmonella contamination

• When animals are infected with Salmonella, the organism will be

shed with the faeces and spread to other animals, soil, water and
crops.

• Animals may get infected with Salmonella through other animals

or through contaminated feed, soil or water.

• Humans may get infected from other humans, directly from

animals or the environment.

• Majority of human cases are caused through contaminated foods

(Poultry and pork meats are often contaminated than cattle)
 Salmonellosis
• It is characterized by fever, diarrhea, abdominal pain and nausea.
• Symptoms are often mild and most infections are self limiting within
a few days.
• This infection may be more serious with severe dehydration and
even death.
• It could be fatal to child(0-4yrs old).
Campylobacter
• Campylobacter jejuni is
predominantly found in
poultry, but can also be
found in cattle, sheep,
goats and pigs.

• Campylobacter coli is
found in meat products,
especially pork and it is
also found in poultry.
 Camplybacter is a gram-negative.
 Temperature range 30-450C.
 They require a microaerobic atmosphere (5% oxygen and 10%
carbon dioxide).
 low-level metabolic activity can be detected at 40C.
 They survive poorly in dry or acid conditions, and in sodium chloride
above 2%.
 They are relatively sensitive to heat and so can readily be
inactivated during cooking.
Sources of Campylobacter contamination

• Campylobacter may be transferred to humans by direct contact with

contaminated animals or animal carcasses or indirectly through the
ingestion of contaminated food or drinking water.
Campylobacteriosis
• The most common symptoms of human Campylobacteriosis include
diarrhoea often bloody, abdominal pain, fever, headache and
nausea.

• Usually infections are self-limiting and last a few days.

• Complications such as arthritis and neurological disorders occur

occasionally.
Yersinia
• Yersinia enterocolitica
• Yersinia pseudotuberculosis.

 Psychrotrophic gram-negative, with a growth potential down to about 0 0C.

 Optimum temperature at 25–370C and may grow up to about 420C.
 Killed by heating.
 Tolerance to pH, water activity and atmosphere comparable to other
enterobacteriaceae.
Symptoms:
 Diarrhoea (may be bloody ).
 Abdominal pain ( infection at the last part of ileum)
 Joint inflammations responsible for arthritis.
 The majority of the cases are caused by Yersinia enterocolitica (few
cases are due to Y. pseudotuberculosis)
Spoilage under aerobic condition

1.) Surface slime, caused by Pseudomonas acinetobacter, Moraxella

alcaligenes ,Streptococcus, Leuconostuoc, Bacillus and Micrococcus.

2.) Change in colour of meat pigment: The red colour of meat may be
changed to shades of green, brown or grey by Lactobacillus and Leconostocs
spp.

3.) Changes in fat: The unsaturated fat in meat gets oxidized by lypolitic
bacteria which produce off odours due to hydrolysis of fats and production
of aldehydes and acids. This type of spoilage is caused by lypolitic
Pseudomonas, Achromobacter and yeast.

4.) Surface color change: The red pigment producing bacteria, Serratia
marcescens, caused red spots on meat. Blue color surface is caused by
Pseudomonas syncyanea and yellow color is caused by Micrococcus species.
5.) Off odor and off taste: Volatile acid like formic, acetic, butyric and
propionic acid produce sour odor and Actinomycetes produce musty or
earthy flavor. Yeast also cause sliminess discoloration and off odor and taste
defects.

6.) Aerobic mould also cause spoilage in meat: These are stickiness,
whiskers, black-spot, white-spot, green patches off odor and off taste.

Spoilage under anerobic condition.

1.) Souring is caused by production of formic, acetic, butyric, lactic, succinic
and propionic acid.

2.) Putrefaction: It is caused by decomposition of proteins under anaerobic

condition by Clostridium species. The foul smell is due to production of
hydrogen sulphide, mercaptans, indol, scatol, ammonia and amines.
 Egg
• Freshly laid eggs are generally sterile particularly the inner contents. However the shells get contaminated from
the environmental sources such as fecal matter of the bird, beddings, by the handlers and wash water and also
the packaging materials in which the eggs are packed.

• There are several extrinsic and intrinsic mechanisms through which the egg protects itself from the microbial
invasion.

 Waxy shell membrane retards the entry of microorganisms. Further, the shell also prevents the entry of
microorganisms. The membranes inside the shell behave as mechanical barriers to the entry of microorganisms.

 Further lysozymes present in the egg white is effective against Gram positive bacteria and avidin in the egg white
forms a complex with biotin, thus making it unavailable for the microorganisms. Also high pH (pH 9-10) of albumin
inhibits the microbial growth.

 Binding of riboflavin by the apo protein and chelation of iron by conalbumin (glycoprotein of egg white albumin)
further helps in hindering the growth of microorganisms that might have gained entry inside the egg.
Spoilage of egg

• Breaks or cracks in egg shell taking place due to transportation or

mechanical damage may allow microorganisms to enter in to the
egg yolk and cause spoilage on storage.

• Eggs on storage may lose moisture and, therefore, weight. The

white of the egg becomes thinner and more watery on storage.

• The major changes in the egg take place due to spoilage

organisms.

• In general the spoilage of eggs is caused by bacteria as compared to

molds and can be described as
 Green rot due to the growth of Pseudomonas fluorescens,
 Colourless rot due to the growth of Pseudomonas, Acinetobacter
and other species;
 black rots due to P roteus, Pseudomonas; red rots due to Serratia
spp. And
 custrad rots due to Proteus vulgaris and Pseudomonas
intermedium.

• Growth of Aeromonas in the egg yolk turns it to black colour and

also there is strong putrid odour due to the formation of hydrogen
sulphide ( H2S ).

• Storage of eggs in high humid atmosphere may help in growth of

several molds on the surface of the egg shell. Molds causing
spoilage of eggs include species of Pencillium, Mucor, Alterneria ,
etc.
Fish Spoilage
• Fish is a very perishable, high-protein food that typically contains a high level of
free amino acids.
Composition of a fish
• Water 65 – 80 % ,Fat 1 – 20 % ,Protein 14 – 20 %
• The lipid content of the fish is up to 25%.
• Fish flesh generally contains less than 1% carbohydrate.
• Non-fatty fish such as teleosts cod, haddock and whiting, the fat levels are only
about 0.5%, while in fatty fish such as mackerel and herring, levels can vary
between 3 and 25%.
• Microbes metabolize these amino acids, producing ammonia, biogenic amines
such as putrescine, histamine, and cadaverine, organic acids, ketones, and
sulfur compounds. Degradation of lipids in fatty fish produces rancid odors .
• In addition, marine fish and some freshwater fish contain
trimethylamine oxide that is degraded by several spoilage bacteria
to trimethylamine (TMA), the compound responsible for fishy off
odors.

• Storage and processing conditions also affect microbial growth.

Pseudomonas and Shewanella are the predominant species on
chilled fresh fish under aerobic conditions.

• Packing under carbon dioxide and addition of low concentrations of

sodium chloride favor growth of lactic acid bacteria and
Photobacterium phosphoreum.

• Heavily wet-salted fish support growth of yeasts while dried and

salted fish are spoiled by molds.
Spoilage of fish and sea foods :

• Halophilic bacteria like Serratia, Micrococcus, Bacillus, Alcaligenes and

Pseudomonas cause spoilage of salt fish.

• Shell fish are spoiled by Acenetobacter, Moraxella and Vibrio.

• Crab meat is spoiled by Pseudomonas ,Acinetobacter and Moraxella at low

temperature and by Proteus at high temperature.

• Microbial loads in shrimps, oysters, and clams depend on the quality of the water
from which they are harvested.

• During handling, faecal coliforms, fecal streptococci, and S. aureus may be

incorporated into the product. Salmonella also is found in oysters possibly due to
contaminated water.

• Seafood also is the source for Pseudomonas spp., C. perfringens, L. monocytogenes,

Vibrio parahemolyticus, Salmonella enterica serovar enteritidis and typhimurium,
Campylobacter jejuni, Yersinia enterocolitica, and Enteroviruses (Hepatitis A).
MICROBIAL SPOILAGE OF FRUITS ,FRUIT JUICES AND VEGETABLES

• Fruits are natural sources of minerals, vitamins besides carbohydrates and other
essential substances.

• Naturally fresh fruits and juices made out of them contain high amount of water
thereby making them highly prone to attack by microorganisms. Besides these
plants also produce certain antimicrobial components too.

• While most of the fruits are naturally provided with coatings and coverings in the
form of skins, but these are fragile enough to be easily disturbed by various
biological and mechanical factors.

• Fruits get contaminated through different sources by a variety of microorganisms

which may play significant role in their spoilage.

• These are soil, water, diseased plant, harvesting and processing equipment's,
handlers, packaging and packing material and contact with spoiled fruits.
Microorganisms Associated with Spoilage in Fruits and Juices

• Despite the high water activity of most fruits, the low pH leads to their spoilage being
dominated by fungi, both yeasts and molds but especially the latter.

• The microorganisms associated with fruits depend on the structure of fruit. The fruits
contain different organic acids in varying amounts.

• The types of acids which are predominately found are citric acid, malic acid and
tartaric acid. The low pH of fruits restricts the proliferation of various types of
organisms.

• Due to the low pH, a large number of microorganisms are restricted to grow on
fruits.

• Fungi are most dominating organisms to grow on fruits because of the ability of
yeasts and molds to grow under acidic conditions.

• A small number of bacteria which are aciduric (ability to resist acidic conditions)
also grow.
Yeasts
• Yeasts are unicellular fungi which normally reproduce by budding.

• Only a few species of yeasts are pathogenic for man and other
animals. None of the pathogenic species are common contaminants
of fruits and fruit products. Fruit that has been damaged by birds,
insects, or pathogenic fungi usually contain very high yeast
populations.

• The yeasts are introduced into the exposed tissue, often via insects,
and are able to use the sugars and other nutrients to support their
growth. Growth of a strongly fermentative.Carbon dioxide and
ethanol are the predominant metabolic products of yeasts, other
products such as glycerol, acetaldehyde, pyruvic acid, and a -
ketoglutaric acid are also formed.

• Oxidative yeasts such as species of Brettanomyces produce acetic

acid in wines and other fruit products.
Molds
• These are filamentous fungi which are important group of microflora of fruit
products due to following reasons

• Some of the members are xerophilic, thereby having potential to spoil foods of
low water activity such as dried fruits and fruit juice concentrates.

• Some of the species have heat resistant spores such as ascospores which can
survive the commercial pasteurization treatments that are given to most fruit
products.
• Growth of molds on processing equipment such as wooden tanks can result in
the generation of off-flavors in wines, juices, and other fruit products.

• The metabolic products of many molds are toxic to humans. Of these toxins,
mycotoxins are important components.

• R. stolonifer cause soft and mushy food ,cottony growth of mold.

• Anthracnose -Colletotrichum lindemuthianum, cause spotting of leaves and

fruits and seedpods
Bacteria
• Various groups of bacteria have ability to grow on fruits and its juices. These bacteria by virtue
of their diversity in metabolism grow on fruits and produce different types of compounds. The
major group of bacteria which are involved are:
• Lactic acid bacteria
• Acetic acid bacteria
• Spore formers

Lactic acid bacteria

• The lactic acid bacteria are Gram-positive, catalase negative organisms which can grow under
anaerobic conditions. These are rod-shaped (lactobacilli), or cocci (pediococci and
leuconostocs) . The homofermentative species produce mainly lactic acid from hexose sugars;
the heterofermenters produce one molecule of lactic acid, one molecule of carbon dioxide, and
a two-carbon compound, which is usually acetic acid or ethanol or a combination of the two.

• Certain heterofermentativee lactobacilli lead to slime in cider. The lactobacilli and leuconostocs
that are present in citrus juices generate acetylmethylcarbinol and diacetyl, compounds that
give the juices an undesirable, buttermilk-like flavor.

• Growth of lactic acid bacteria in juices and other fruit products cause the formation of haze,
gas, acid, and a number of other changes.

• Some strains, being extremely tolerant to ethanol grow in wines. Lactobacillus fructivorans can
grow in appetizer and dessert wines containing as much as 20% ethanol.
Acetic acid bacteria
• These are Gram negative, aerobic rods having two genera, viz. Acetobacter and
Gluconobacter . Both of these species oxidize ethanol to acetic acid under acidic
condition.
• Because the bacteria are obligate aerobes, juices, wines, and cider are most
susceptible to spoilage. Some strains of Acetobacter pasteurianus and
Gluconobacter oxydans produce microfibrils composed of cellulose, which leads
to formation of flocs in different fruit juice beverages.

Spore formers
• Spores are heat resistant, so role of organisms producing spores is important in
heat treated juices and beverages. Various spore formers such as Bacillus
coagulans, B. subtilis, B. macerans, B. pumilis, B. sphaericus , and B.
pantothenticus have been found to grow in different types of wines.

• Some of these organisms have also been involved in canned fruits. Spore-
forming bacilli that actually prefer a low pH have been responsible for spoilage of
apple juice and a blend of fruit juices.
 MICROBIAL SPOILAGE OF VEGETABLES

• Vegetables form an integral part of diet due to their role in providing various types of vital
nutrients such as carbohydrates, minerals, vitamins, roughage etc. Vegetables being a part
of fresh produce, contain high moisture which makes them highly perishable foods and
hence more prone to spoilage.

• Microorganisms gain entry into vegetables from various sources. These sources include:
 Soil
 Water
 Diseased plant
 Harvesting and processing equipments
 Handlers
 Packaging and packing material
 Contact with spoiled vegetables
 The conditions in which vegetables are stored and transported after harvesting also
contribute to rate of spoilage. Other than microbial, sources, the spoilage of vegetables
can also occur due to the activity of native enzymes.
Types of Spoilage in Vegetables
• The microbial spoilage of vegetables is predominately of following types
Spoilage due to pathogens
• The plant pathogens which infect stem, leaves, roots, flowers and other parts
or the fruit itself.

Spoilage due to saprophytes

• Vegetables have general microflora inhabiting them. These organisms under
certain conditions can grow on these vegetables and spoil them. There are
certain secondary invaders which may enter the healthy food or grow after
growth of pathogens.

• It is well known that plant diseases are mostly caused by fungi. Thus most of
the spoilage causing pathogens in vegetables are fungi. The fungi produce
characteristic spores which may be pigmented. The pigmentation helps in
identification of the type of spoilage by fungi.

• The bacterial diseases too cause spoilage of vegetables but to a lesser extent.
• Spoilage in vegetables is largely affected by composition of vegetable.
The non acidic foods are thus spoiled by bacterial rot while acidic
foods with dry surfaces are more prone to mold spoilage.

Bacterial Soft Rot

• Caused by Erwinia carotovora and Pseudomonas such as P.
marginalis. Bacillus and Clostridium spp. are also implicated.
• Breaks down pectin, giving rise to a soft, mushy consistency,
sometimes a bad odour and water-soaked appearance.

• Vegetables affected- onions, garlic, beans, carrot, beets, lettuce,

spinach, potatoes, cabbage, cauliflower, radishes, tomatoes,
cucumbers, watermelons.
Fungal spoilage of vegetables
• Penicillium, Cladosporium, Rhizopus, Aspergillus spp. are responsible
for various defects in vegetables.

• Gray mold rot – caused by Botrytis cinera in vegetables. Favoured by

high humidity and warm temperature