Cheese and kefir are the important spin -off from microbes. These products often get contaminate by various process. Due to large scale commercialization and consumerism many techniques are performed.

1. D.SAROTHIKA
REG NO: 1701721077026
FOOD MICROBIOLOGY
CA-3
CONTAMINATION AND THE SPOILAGE OF CHEESE
AND KEFIR

2. CHEESE
• Cheese is a dairy product derived from milk that is produced in a wide range
of flavors, textures, and forms by coagulation(curdles) and whey separation
of the milk protein casein.
• It comprises proteins and fat from milk, usually the milk of cows, buffalo,
goats, or sheep. Most cheeses melt at cooking temperature.
• There are more than 1000 varieties of cheese have been processed all over
the world.
• Each type of cheese differs in production, taste, color, shape and etc.,

3. PRODUCTION:
BASIC STEPS INVOLVED:
1. Coagulation of milk to form a curd.
2. Separation of the curd from the whey.
3. Shaping of the curd.
4. Ripening to achieve flavor and texture.

4. MICRO ORGANISMS INVOLVED IN THE CHEESE PRODUCTION:
• Mostly lactic acid bacteria(LAB) species is widely used in the production of cheese. Based on the
variety of cheese bacterial species differs.
• Cremoris species used for the production of Cheddar.
• Streptococci- Streptococcus salivarius thermophilus used in Mozzarella.
• Lactobacilli-Lactobacillus helveticus used in Swiss and alpine cheeses.
• Propionibacterium freudenreichii species shermanii is a specific bacterium that converts lactic
acid into carbon dioxide, propionic acid and acetic acid. The C02 seeps into the cheese body and
produces the eyes.
• GOUDA cheese often have eyes as well, although usually to a smaller degree than Swiss.
• Leuconostoc mesenteroides, Lactococcus lactis, L. biovar, L. diacetylactis which also gives (buttery
flavor).

5. MOLDS:
• The two main molds that are found in cheese are blue and white. There are many
molds that grow naturally on the surfaces of cheese during affinage.
• WHITE MOLD:
Penicillium camemberti, P. candidum are the most popular species that responsible
for the nice white lawn on the surfaces of cheeses like camembert and brie.
• BLUE CHEESE:
P.roqueforti and P. glaucum are widely used. These molds are living breathing
organisms.

6. EFFICIENT STRAINS WITH MORE PRODUCTIVE ARE CHOSEN.
IT SHOULD BE ECONOMICALLY PROFITABLE TO THE INDUSTRY.
SHELF LIFE AND FLAVORS ARE CONSIDERED PURPOSELY.

7. REASONS FOR VARIETIES AND SPOILAGE IN CHEESE:
• Type of milk or milk fractions used
• Temperature : high-hard, low-soft
• Acidity- putrefactive bacteria, amount of
lattice acid produced
• Humidity controls the growth of moulds
• The type of precipitating agent used.
• Amount of pressure used to remove
moisture
• Use of salt, it affect the growth of bacteria
• Length of time for ripening
• The addition of molds or bacteria
• The type and the size of the moulds.

8. MAJOR CLASSES OF CHEESE:
CLASS OF CHEESE TYPE
White Mold Cheese Camembert
Blue Mold Cheese Roquefort
Red Surface Bacteria Cheese Limburger
Hard-grating Cheese Parmesan
Cheese with eyes Swiss
Pasta filata Cheese Mozzarella
Hard Cheese Cheddar, Colby, Marble
Semi-hard Cheese Double Gloucester, Edam and Gouda
Soft, unripened Cheese Cottage cheese, Hoop Cheese
Whey Cheese Ricenster, Ricotta Cheese, Mysost, Brunost Cheese
Sour Milk Cheese Harzer
Bacterial Ripened Cheese Brick, Parmesan
Semi Soft Cheese Muenster, Talleggio
Processed Cheese American Cheese

9. FACTORS INFLUENCING MICROBIAL GROWTH
1. Water Activity
2. Concentration of the salt
3. Oxidation-reduction potential
4. Nitrate
5. Temperature
6. The production if bacteriocins by some micro organisms.
These factors are called ‘HURDLES’.
The effect of the individual hurdles may not be significant, but all of them
acting together lead to considerable control.
Other compounds produced during curd manufacture and ripening, for
example, water and , also inhibit microbial growth, but the
concentrations of these produced by the starters in cheese are not
sufficiently high to have a significant effect on the bacteria.

10. WATER ACTIVITY:
• All microorganisms require water for growth, but it is the availability of the water,
rather than the total amount present, that is the important factor.
• Water availability is measured by water activity (aw), which is defined as the
“Ratio of the vapor pressure over the cheese to the vapor pressure of pure water at
that temperature.
• NaCl and organic acids (lactate, acetate, and propionate) dissolve in the moisture
in the cheese and reduce the vapor pressure.
• The greater the concentration of these compounds, the lower the aw.
• Cheese, unless vacuum packed, loses moisture by evaporation during ripening.
• This results in a gradient in the aw of the cheese (lower on the outside than on the
inside).
• The aw gradient is generally much greater in large cheeses than in small ones.
• Proteins in cheese are hydrated, and this ‘bound’ water is not available for bacterial
growth (aw >0.92).
• The limit for most yeasts is 0.83, whereas that for molds is 0.75; osmophilic yeasts
grow at aw values < 0.60. An aw value of <0.92 is equivalent to a salt
concentration of 12.4%.
• Hydrolysis of proteins to amino acids and peptides and lipids to acylglycerols and
fatty acids during ripening reduces the availability of water, as one molecule of
water is added at each bond hydrolyzed.

11. SALT CONCENTRATION:
• The action of salt is intimately connected with
the reduction in aw that occurs when salt (or
any solute) gets dissolved in water.
• In cheese, the salt concentration varies from
perhaps 0.4% in Emmental cheeseto 5% in Blue
cheese.
• In calculating the inhibitory effect of salt in
cheese, it is the amount of salt dissolved in the
water(SM)of the cheese, rather than the actual
concentration of salt, that is the important
parameter.
• The SM in Cheddar cheese varies from 4 to 6%.
• Most cheeses are brine-salted – Cheddar is an
exception and is dry-salted. In brine-salted
cheeses, a salt gradient (outside higher, inside
lower) exists at the beginning of ripening,
which decreases relatively slowly during
ripening.
• All brined cheeses contain a high level of salt in the
surface layers; therefore, the secondary
microorganisms growing on the surface must be
salt-tolerant. Most coryneforms, micrococci, and
staphylococci can grow in the presence of 10–15%
NaCl.
• The growth of P. camemberti is largely unaffected
by 10% NaCl, and some strains of P. roqueforti can
tolerate 20% NaCl.
• Geotrichum candidum is quite sensitive to salt.
• In the presence of 1% NaCl, its growth may reduce
at 1% NaCl and it is completely inhibited at 6%.
Therefore, too much brining will prevent its growth
on the cheese surface.
• Its intolerance to salt may explain why G.
candidumis generally deliberately added in the
manufacture of surface-ripened cheeses, the hope
being that some cells will grow.

12. PH AND OTHER ORGANIC ACIDS:
• Most bacteria require a neutral pH value for optimum growth and exhibit poor
growth at pH values < 5.0.
• The pH of cheese curd after manufacture generally lies within the range of 4.5–5.3, so
the pH is a significant factor in controlling bacterial growth in cheese.
• LAB, especially lactobacilli, generally have a pH optimum below 7, and Lactobacillus
species can grow at pH and molds have an optimum pH of 5–7 butcan grow at pH
values < 3.0 Coryneforms and micrococci are thought to be unable to grow below pH
5.5 or 6.0.
• The efficacy of organic acids as inhibitors of microbial grow this thought to depend on
the amount of undissociated acid present and therefore on the dissociation constant
(pKa) and pH.
• The principal acids found in cheese are propionic, acetic and lactic, and the values of
4.87, 4.75 and 3.08, respectively so that at the same concentration lactic acid is the
least and propionic the most effective inhibitor.
• However, the concentration of the acid is also important and, in cheese, lactate is
invariably present in young cheese curd at much greater concentrations than those of
the other two acids.
• The pH of many soft cheeses characteristically increases during ripening, particularly
on the surface, and this will reduce the inhibitory properties of the surface.
• Propionic acid is very effective at repressing the growth of molds.

13. NITRATE
• Nitrate (NO3-), as KNO3 (saltpeter)or NaNO3, is
added to the milk (20 g 100 l to the power 1) for
some cheeses, especially Dutch-type cheeses like
Goudaand Edam, to prevent early and late
production of gases by coliforms and Clostridium
tyrobutyricum respectively.
• Thereal inhibitor is NO2-, which is formed from
NO3- by xanthine oxidoreductase in the milk or
curd.
• The exact mechanism by which NO2- prevents
microbial growth is not clear.
• NO2- is an effective inhibitor for clostridia, but it
does not inhibit coliforms.

14. TEMPERATURE:
• Higher temperatures promote faster ripening by the starter and non-starter microorganisms but
also allow the growth of spoilage and pathogenic bacteria.
• Generally, Cheddar cheese is ripened at 6–8 degreeC, whereas mold- and smear-ripened cheeses
are ripened at 10–15 degree Celsius.
• Emmental cheese is ripened initially for 2–3 weeks at a low temperature (12 degree Celsius),
after which the temperature is increased to 20–24 degree Celsius and maintained for 2–4 weeks
to promote the growth of PAB and the fermentation of lactate to propionate and acetate; the
temperature is then reduced again to 4 degree Celsius.
• For soft cheeses, the humidity of the environment is also controlled to prevent excess
evaporation of moisture from the cheese surface.

15. ORGANISM RESPONSIBLE FOR CHEESE
CONTAMINATION:
ENTERIC BACTERIA:
Salmonella species
Camylobacter jejuni
Yersinia
Escherichia coli (enteropathogenic strains)
Shigella
ENVIRONMENTAL BACTERIA:
L . Monocytogenes
VIRUSES:
Norwalk
Hepatitis A
Parasite:
Cyclospora
Crytospordium
Giardia

16. PHYSICAL HAZARDS:
(PRODUCTION, PROCESSING, STORING, DISTRIBUTION)
GLASS :
Bottles, jars, light fixtures, gauge covers
Metal:
Shavings, equipment parts, cheese molds, wires from cheese harps, screens
Plastic :
Packaging material, pallets, equipment covers, cheese molds
Wood:
Pallets, boxes, building structure, aging boards.
Maintenance of formages properly, cleaning regularly
High levels of exposure of employees.
Away from mites and insects.

17. CHEMICAL HAZARD:
• DRUG RESIDUES:
Antibiotics or any other preservatives used in the cheese or in any raw materials may
also contamination if the ratio is slightly high or low.
• VITAMINS:
Addition of vitamin A and D for fortification.
Vitamin fortification of fluid milk products.
• MYCOTOXINS:
Produced by some mold strains.
Can be a problem with diary animal feed
Illness includes gastroenteritis, liver disease, cancer, death
• PESTICIDES:
Materials used in the plants or its products as raw materials.

18. BIOLOGICAL HAZARD:
• Nutrition to pathogenic micro organisms
• Fertilizers used in plants consumed by cows
• Inadequate acidification
• Improper cleaned equipment
• Biofilms on equipment
• Contaminated water
• Cheese mites
• Cross- contamination

19. BIOLOGICAL HARZARD INTOXICATION:
Consumption of preformed toxins
Usually large numbers of pathogens are need to produce sufficient toxin to cause illness
Some toxins are very heat stable and may persist after the vegetative pathogens are
destroyed.
Bacillus cereus
Bacteria
Fungi
Viruses
Parasites
Clostridium perfringens
Staphylococcus aureus
Clostridium botulinum

20. CHEESE POISONING ALSO INCLUDES:
POOR STARTER ACTIVITY PRESENCE OF ANTIBIOTIC POOR HYGIENE
GROSS ENVIRONMENTAL
CONTAMINATION
FAULTY PASTERIZATION
NORMAL FLORA PRESENT
IN HUMANS (PROCESS OF
HANDLING)
STERILITY OF THE
INSTRUMENTS
USING MUTANT STRAINS

21. THINK BEFORE EAT!
HEALTHY CHEESE
• A good cheese should be rich in
Vitamin B12, Zinc, Riboflavin,
Vitamin A , K2, Probiotics
• Calories and energy source vary
from one type of cheese to other.
• Source of protein, carb, fats and
probiotic nature.
• FETA, Mozzarella, Italian Ricotta,
Cottage cheese and Gouda are the
best cheeses.
• Strengthen bones, contains anti-
cancer properties, prevents
osteoporosis, improves skin health,
rich in antioxidant, promotes weight
gain, eye, brain and heart health,
helps to lower stress
UNHEALTHY CHEESE
• Cheese has high amount of
sodium content which may cause
blood pressure and kidney
problems.
• Halloumi, blue cheese, Parmesan,
cheddar and Roquefort cheese.
• Full of saturated fat, gains weight
and leads to obesity and also
cause cardiovascular system.
• Excessive sodium may also
Diabetes, Stiff Blood Vessels,
stroke and heart attack.
• They also contains hidden molds.
• More cheese and meat leads to
cancer.

22. SHELF LIFE OF CHEESE:
The shelf life of cheese can vary from a
few weeks to multiple years depening
on its composition and how it is
packaged. L
Low-moisture, hard cheese (like
parmesan) have a shelf life that ranges
from 10 month to several years
Expired cheese smells like sour milk
Soft cheeses tend to spoil more quickly
than hard or aged cheeses.
Stored properly, an unopended packet of
hard cheese like parmesan or cheddar
can be kept in the fridge for between 2-4
months or 8 in the freezer.
Consuming expired cheese may cause
vomiting, stomach pain and diarrhea
and also leads to death

23. CASU MARZU – ROTTEN CHEESE
I am not contaminated but people enjoy
me with live and energetic magggots……
and they say yum!!!
It is also known as “CASU MODDE” or “CASU
CUNDIDU” or “CASU FRAZIGU” in Sardinia, is
traditional Sardinia sheep milk cheese that
contains live insect larvae (maggots).
The preparation of the cheese goes beyond
typical fermentation to a stage of decomposition,
brought about by the digestive action off the
larvae of the cheese fly Piophilia casei.
The texture becomes very soft with some liquid
seeping out.

24. CONTAMINATION IN THE KEFIR
THE BAD MICROBES

25. KEFIR:
• Kefir is a cultured, fermented beverage that tastes like yogurt
drink.
• It is made using “starter” grains, just as sourdough bread.
• This starter is a combination of yeasts, milk, proteins and
bacteria.
• It has a tart, creamy flavor and it’s loaded with probiotic health
benefits.
• Kefir is most commonly made with diary milk, but it can be
made with non-diaryalternatives including coconut milk, goat’s
milk, rice milk and coconut water.
• Because kefir is fermented, most people are lactose intolerant
can actually drink kefir.

26. PRODUCTION OF KEFIR:
The production of kefir involves a
mixture of bacteria and yeasts
The milk is pasteurized to
remove endogenous microflora
and then a specific mixture of
bacteria(Lactobacillus caucasius)
along with two yeasts
(Saccharomyces kefir and Torula
kefir ) are added.
TYPES OF KEFIR ARE:
Milk kefir
Water kefir

27. MICRO ORGANISMS USED IN THE KEFIR PRODUCTION:
• Kefir Starter Culture is made of freeze-dried bacteria, similar
to our yougurt starter culture.
• It is a powdery substance that is used to activate kefir.
• Both starter and grains contain several different strains of
bacteria and a specific type of mesophilic symbiotic culture.
• The main difference between kefir starter an kefir culture is
bacteria in the starter is freeze-dried that is sleeping and it
requires no maintenance if it is not using it to make kefir,
while the bacteria in the grain is aive and need to keep it alive
for as long as to use the grains to make kefir.
• Some of the starter cultures are Bifidobacterium species,
Lactobacillus species and probiotic yeast (Saccharomyces
boulardii) may be used as adjunct cultures when blended
with kerfir grains.

28. PROBIOTIC BACTERIA FOUND IN KEFIR ARE:
• Bifidobacterium bifidum
• Streptococcus thermophilus
• Lactobacillus delbrueckii
• Lactobacillus helveticus
• Lactobacillus kefiranofaciens
• Lactococcus lactis
• Leuconostoc species
• Lactobacillus acidophilus
• Lactobacillus brevis
• Lactobacillus casei
• L. bulgaricus

29. PATHOGENS PRESENT IN KEFIR :
 Salmonella genus
 Escherichia coli
 Staphylococcus aureus
 Listeria monocytogens
 Salmonella typhimurium
 Salmonella enteritidis
• The fermentation that is caused by
micro organisms in the kefir grins
triggers a more intense
acidification process in kefir than
that in milk without addition of
these grains.
• The ph changes highly influence
kefir and its taste.

30. MICRO ORGANISMS:
• The micro organisms in the kefir grains produce lactic acid,
antibiotics and bactericides which inbihit the development of
degrading and pathogenic micro organisms in kefir milk.
• Kefir acts against the pathogenisc micro organisms Salmonella,
Helicobacter, Shigella, Staphylococcus, E.coli, Enterobacter
aerogenes, Proteus vulgaris, Bacillus subtilis, Micrococcus luteus,
S. pyrogenes, S.faecalis and the fungus Candida albicans.
• It had been proved that many species of lactobacilli present in
kefir have S- layer proteins.
Flavourised kefir

31. BENEFITS OF KEFIR:
• It is high in calcium, amino acids, B-vitamin and folic acid
• Development of a healthy digestive tract in babies, as it protects against
negative effects of radiation and helps to improve the immune system.
• Kefir also acts as anti-carcinogenic agent and also helps to enhance bowel
function and control candida - reduce the excess growth of yeast cells.
• It is also a mild laxative properties
• Good sources of vitamin b12, b1, and k and also excellent sources of
biotin.
• Because kefir is such a balanced and nourishing food, it contributes to a
healthy immune system and has been used to help patients suffering
from AIDS, chronic fatigue syndrome, herpes and cancer.
• The benefits also seen in disorders, depression and ADHD patients.

32. THANK YOU MAM!
D. SAROTHIKA
REG NO: 1701721077026
!