The document discusses various processes used in milk production and preservation including pasteurization, sterilization, evaporation, and drying. It describes methods of pasteurization like high temperature short time and low temperature long time. It also explains milk products like butter, ghee, condensed milk, dry milk, and cheeses along with how enzymes and additives are used in their production.

1. Dr.D.KANCHANA
MICROBIOLOGY

2. Definitions
• Raw milk: The lacteal secretion , practically free
from colostrum, obtained by the complete milking
of one or more healthy cows (PMO).
• “Consumer Milk” products:
- Homogenized milk: 3.25% fat
- Reduced fat milk: 2% fat
- Low fat milk: 1% fat
- Fat-free milk: skim milk, <0.5% fat
(all with 8.25% solids-non-fat)
• Other “milk products”: lactose reduced milks, heavy cream,
cultured milks, yogurt, cottage cheese.

4.  Milk is sterile at secretion in the udder but is
contaminated by bacteria even before it leaves
the udder.
 Further infection of the milk by microorganisms
can take place during milking, handling, storage,
and other pre-processing activities.

5. Streptococcus lactis
Achromobacter
Coliform bacteria
Bacillus subtilis

7. Pasteurization
Sterilization
Dehydration

8. • Purpose: Inactivation of bacterial pathogens (target
organisms Coxiella burnettii)
- assurance of longer shelf life (inactivation of
most spoilage organisms and of many enzymes)
• Pasteurization
– Heat treatment of 72ºC (161°F) for 15 sec (HTST)
or 63ºC (145°F) for 30 min (or equivalent)
– does not kill all vegetative bacterial cells or spores
(Bacillus spp. and Clostridium spp.)
– Pasteurization temperature is continuously
recorded
Pasteurization

9.  Pasteurization is a process of heating a food,
which is usually a liquid(milk), to a specific
temperature for a predefined length of time
and then immediately cooling it after it is
removed from the heat.
 This process slows spoilage caused
by microbial growth in the food.

10.  The French scientist Louis Pasteur invented
pasteurization.
 To remedy the frequent acidity of the local wines he
found out experimentally that it is sufficient to heat
a young wine to only about 50–60 °C (122–140 °F)
for a brief time to kill the microbes.
 Pasteurization was originally used as a way of
preventing wine and beer from souring, and it would
be many years before milk was pasteurized.
 Pasteurization of milk was suggested by Franz von
Soxhlet in 1886.

12. 1
• High Temperature, Short Time(HTST method)
• Low Temperature, Long Time(LTLT method)
2
3
• Ultra High Temperature Pasteurization(UHT method)
4
• Vat Pasteurization

13.  Temperature of about 63ºc(145ºF) maintained
for 30 minutes is called holding method (or)
LTLT method

14. This involves following steps.
Milk is pumped through a stainless steel heat-
exchanger
↓
passes across one side of a series of plates which
are in contact with hot water on the other side
↓
Milk emerges from the heat exchanger and
passes into a stirred tank

15. ↓
It is held for 30 min at 65ºc
↓
This tank is preferably fitted with a temperature
recorder clamped to a clock to ensure that the
temperature is maintained long enough to
destroy the bacteria
↓
At the end of the 30 min. the milk is run out over
a surface cooler or through another heat-
exchanges in which cold water is run
countercurrent to the milk on reverse side of the
plates

16.  The HTST pasteurization standard was designed to
achieve a five-log reduction, killing 99.999% of the
number of viable micro-organisms in milk.
 This method requires that the milk be held at 161
degrees for 16 seconds. This process, also refereed to
as continuous flow pasteurization, requires the milk to be
forced through metal pipes that are heated from the
outside.

17. This involves following steps
raw milk
↓
Regenerator (heated)
↓
Flow access the other side of the heat
exchanger plates
↓
The milk is raised to pasteurizing temperature

18. ↓
passes through the heater unit and remains
at this temperature for the time it takes to
flow through holding tubes
↓
It is then cooled first by passing through the
regenerator and then through the cooler

20.  It produces a product that has a stable shelf
life of up to two months.
 UHT processing holds the milk at a
temperature of 138°C (280°F) for a minimum
of two seconds.
 After treatment it can pass through a heat-
exchanger or by direct ingestion of live steam
so called tetra pack process.

22.  Vat Pasteurization is the most gentle type
of pasteurization.
 The milk is held in a heated vat at 145
degrees for 30 minutes. It is then quickly
cooled to 39 degrees.

24.  Sterilization is a term referring to any process that
eliminates or kills all forms of microbial life, including
transmissible agents (such as fungi, bacteria, viruses,
spore forms, etc.) present on a surface, contained in a
fluid, in medication, or in a compound such as
biological culture media.
 Sterilization can be achieved by
applying heat, chemicals, irradiation,high pressure,
and filtration or combinations thereof.

25. Tyndalization
 Named after John Tyndall is a lengthy process designed to reduce
the level of activity of speculating bacteria that are left by a simple
boiling water method.
 It involves boiling for a period (typically 20 minutes) at atmospheric
pressure, cooling, incubating for a day, boiling, cooling, incubating
for a day, boiling, cooling, incubating for a day, and finally boiling
again.
 The three incubation periods are to allow heat-resistant spores
surviving the previous boiling period to germinate to form the heat-
sensitive vegetative (growing) stage, which can be killed by the next
boiling step.
 This is effective because many spores are stimulated to grow by the
heat shock. The procedure only works for media that can support
bacterial growth - it will not sterilize plain water.

26.  Boiling milk or heating in flowing steam
destroys all microorganisms except spores of
bacteria and changes the appearance,
palatability, digestibility, and nutritive
properties of milk.

27.  Evaporated milk is canned and then heat
processed by steam under pressure. Often
with accompanying rolling or agitation.
 The fore warming of milk at about 93-100ºc
or higher before evaporation kills all but the
more resistant bacterial spores.
 Sealed cans of evaporated milk are processed
at 115ºc-118ºc for 14-18 min, which results
in a commercially sterile product.

28.  A Raw milk for pasteurization should be
cooled at 10ºc or less within 2 hr after being
drawn and kept that cold until processed.
 Newly pasteurized milk is to be cooled to
7.2ºc or less and maintained there. It is
preferable, of course, to cool it to
temperatures well below 7º-10ºc.

29.  Butter in storage is held at -17º to -18ºc or
lower, where no microbial growth can take
place.
 Frozen cream is stored in considerable
amounts at a similar temperature.

30.  Microfiltration is the process of filtration
with a micrometre sized filter.
 Microfiltration is a membrane
technical filtration process which
removes contaminants from a fluid by
passage through a
microporous membrane. A typical
microfiltration membrane pore size
range is 0.1 to 10 micrometres (µm).

31. Milk
MILK
Milk

32.  Dehydrated milk is manufactured dairy product made by
evaporating milk to dryness.
 Purpose- to preserve it; milk powder has a far longer shelf
life than liquid milk and does not need to be refrigerated,
due to its low moisture content.
 Dry milk is also easy to transport.
 First invented by Russian physician Osip Krichevsky in
1802.
 Commercially available in 1832 by Russian chemist M.
Dirchoff.

33.  Evaporated milk is made by removing about 60%
of the water from whole milk, so that about
11.5% lactose would be in solution plus twice the
amount of soluble inorganic salts in whole water.
 This high concentration of sugar is inhibitory to
growth of some bacteria. Condensed milk is
more concentrated than evaporated milk and is
still a poor culture medium for organisms not
tolerant of high sugar concentrations.

34. Milk
drying
methods
Spray
Drying
Drum
Drying
Freeze
Drying

35. • Pasteurized milk is first concentrated in
an evaporator to approximately 50% milk
solids. The resulting concentrated milk is
then sprayed into a heated chamber where
the water almost instantly evaporates, leaving
fine particles of powdered milk solids.
Spray Drying
• Milk is applied as a thin film to the surface of
a heated drum, and the dried milk solids are
then scraped off. However, powdered milk
made this way tends to have a cooked flavor,
due to caramelization caused by greater heat
exposure.
Drum Drying
• Same as drum drying but involves freezing
which retains more amount of nutrition.
Freeze
Drying

36.  used in the manufacture of infant
formula, confectionery such as chocolate
and in recipes for baked goods where
adding liquid milk would render the product
too thin.
 used in various sweets such as the famous
Indian milk balls known as Rasgulla and
popular Indian sweet delicacy.
 common item in UN food
aid supplies, fallout shelters and is favored
by survivalists, hikers, and others requiring
nonperishable, easy-to-prepare food.
 Reconstruction-one cup of potable fluid
milk from powdered milk requires one
cup of potable water and one-third cup
of powdered milk.
This is the original container from
1947, provided by the Ministry of
Food in London, England

38.  Condensed milk is cow's milk from
which water has been removed. It
is most often found in the form
of sweetened condensed milk, with
sugar added.
 Sweetened condensed milk is a
very thick, sweet product which
when canned can last for years
without refrigeration if unopened.

39.  Raw milk is clarified and standardised, and then is heated to 85-
90°C for several seconds.
 This heating destroys some microorganisms, decreases fat
separation and inhibits oxidation.
 Some water is evaporated from the milk and sugar is added to
approximately 45%. This sugar extends the shelf life of sweetened
condensed milk.
 Sucrose increases the liquid's osmotic pressure, which prevents
microorganism growth.
 The sweetened evaporated milk is cooled and lactose crystallization
is induced.

40.  sweetened condensed milk is the preferred milk to be added to
coffee or tea.
 Many countries in Southeast Asia, use condensed milk to flavor their
coffee.
 A popular treat in Asia is to put condensed milk on toast and eat it in
a similar way as jam and toast.
 Condensed milk is an alternative to jam.
 It is a major ingredient in many Indian desserts and sweets. While
most Indians start with normal milk to reduce and sweeten it,
packaged condensed milk has also become popular.

41.  The use of sorbic or propionic acid or one of
their salts is permitted in cottage cheese, yogurt
and some of the hard cheese and processed
cheese.
 The addition of preservatives to cottage cheese
and yogurt is to prevent growth of moulds on the
surface of product and to extend its shelf-life.
 Added sugar acts as a preservative of sweetened
condensed milk and also it reduced the moisture,
there by making moisture unavailable to
microorganisms.

42.  Sodium chloride or common salt is added in
the manufacture of various kinds of cheese,
but usually it is more of flavour or for
controlling the growth of microorganisms
during manufacturing and curing than for
preservation of finished product.
 Carbonation of milk, butter, and ice cream
has been tried as an aid in preservation but
without much success. Cheese is smoked
primarily for the addition of flavour, although
the drying, especially of the rind chemical
preservative from smoked may improve
keeping quality.

43.  Mold spoilage of cheese is delayed or prevented
sorbic acid, propionic acid, sorbates or
propionates are added or incorporated in the
wrapper.
 The addition of hydrogenperoxide combined with
a mild heat treatment has been used for
pasteurization of milk for certain kinds of cheese
(e.g. swiss and cheddar).
Developed preservatives
 most fermented products are microbiologically
more stable have a longer shelf-life than initial
substrate. Fermented milk and cheese are
preserved partly by developed acidity produced
by the bacterial culture and therefore have a
longer shelf-life than fluid milk

44.  The enzymes proteinases, lipases, lactase, beat-
galactosidase, rennin(chymosin), and fruit enzymes
are used in milk product.
 At present 4 proteinases, bovine and porcine pepsins
and acid proteinases of mucor michei and m.pusillus
are regarded as suitable substitutes of rennet.
 Lipases cause considerable food spoilage through
hydrolytic rancidity.
 The principal application of lipases is in cheese
manufacture, particularly hard italian varieties.

45.  Lactose is the most dominant carbohydrate in
the milk. The presence of lactose in some
food preparation is desirable to stabilize
flavour, taste and texture and as a reducing
agent to bring about mailard browning as a
source of desired flavour and colour.
 Beat-galactosidase is widely distributed in
plant, animal and microbial sources; only the
enzymes from Aspergillus niger,
Kluyveromyces lactis, K.fragilis and E.coli are
commercially available.

46.  Rennin, an enzyme secreted by the young
calves, bring about the coagulation of the
milk.
 Rennin act as a general proteolytic enzyme on
all the protein components.
 When casein is precipitated by the action of
rennet, the calcium is not released to the
whey but remain attached to the casein
therefore, cheese made with rennet is a much
better source of calcium than cheese made by
acid precipitation alone. Cottage cheese is
often made by acid precipitation.

47.  Bromelin, a proteolytic enzyme, from pineapple
digests proteins hence changes the gelation to
compounds that do not form gel. The enzyme
bromelin clots the milk and digests the clot.
 All fruits contain some organic acids but not
always in sufficient concentration to cause the
curding of milk.
 Destroying of the enzymes before combining the
fruit with milk prevents curdling caused by the
enzyme action, by blanching or by using canned
fruits.

48.  Salting acts as an antiseptic, slows down
the development of microorganisms,
improves the storage life of the cheese and
speeds up the drying process and the
formation of a rind.

49. ●Curd(dahi) ●Buttermilk
●Butter ●Ghee
●Evaporated milk ●Condensed milk
●Toned milk ●Dry milk
●cheese

50.  Cheese
• Cheese is a food derived from milk that is produced in a
wide range of flavors, textures, and forms by
coagulation of the milk protein casein. It comprises
proteins and fat from milk, usually the milk of cows,
buffalo, goats, or sheep.
• During production, the milk is usually acidified, and
adding the enzyme rennet causes coagulation.

51. Fresh cheeses
Fresh or unripened cheeses are coagulated under the
action of lactic acid fermentation in the milk instead
of adding rennet. While they are drained after
formation of the curd, they are neither ripened nor
fermented.
This category includes cottage cheese, ricotta,
mascarpone, cream cheese and quark. Fresh
cheeses are mainly used in baking and desserts,
plain or flavored with vegetables, fruits, herbs or
spices.

52.  Soft cheeses
• Soft cheeses are ripened for a relatively short period of
time before being drained and turned into molds
without being pressed or cooked.
 They have a moisture content of 50% to 60% and their
fat content represents 20% to 26% of the cheese’s
weight
Blue-veined cheeses
 Blue-veined (or blue) cheeses are neither cooked nor
pressed; the curd is inoculated with a species of blue-
green mold, which is injected into the cheese by means
of long needles.

53. • Butter is a dairy product that consists of butterfat, milk
proteins, and water. It's made by churning fresh or
fermented cream or milk. It is used as a spread and a
condiment—and in cooking, such as baking, sauce
making, and pan frying.
• Commonly made from cows' milk, butter can also be
manufactured from the milk of other mammals,
including sheep, goats, buffalo, and yaks. Producers
sometimes add Salt, flavorings, or preservatives.

54. PRODUCT TEMPERATURE
(℃)
RH (%) SHELF LIFE
CHEESE
Blue 0-1.1 70 3-6 months
Cheddar 0-1.1 70 12 months
Cream 0-1.1 70 4 weeks
Pasteurized 0-4.4 6-10 months
Swiss 0-4.4 70 8-12 months
MILK
Evaporated 0 +1 year
Condensed 4.4 6-12 months
10 Few months
21.1 Few weeks
HTST 2-3 weeks

55. PRODUCT TEMPERATURE
(℃)
RH (%) SHELF LIFE
HTST 1.6-4.4 2-3 weeks
1.4-7.2 1-2 weeks
UHT 1.6-4.4 +1 months
Non-fat dry milk 4.4 60 10 months
21.1 60 5 months
37.7 60 2 months