Milk is the food which exclusively sustains us during the first few months of life. In addition to being a nutritious food for humans, milk provides a favorable environment for the growth of microorganisms. Yeasts, moulds and a broad spectrum of bacteria can grow in milk, particularly at temperatures above 16°C. Microbes can enter milk via the cow, air, feedstuffs, milk handling equipment and the milker. Raw milk : The lacteal secretion , practically free from colostrum, obtained by the complete milking of one or more healthy cows(PMO).

1. MICROBIOLOGY OF MILK
& MILK PRODUCTS
Presented by:
Farwa Butt
Muhammad Alfahad

2. TABLE OF CONTENTS
 Introduction……………………………………
 Composition of milk…………………………..
 Physical properties
 pasteurization of milk…………………………
 Sterilization of milk…………………………..
 Milk products…………………………………
 References…………………………………….

3. INTRODUCTION
Milk is the food which exclusively sustains us during the first few months of life.
 In addition to being a nutritious food for humans, milk provides a favorable
environment for the growth of microorganisms. Yeasts, moulds and a broad spectrum of
bacteria can grow in milk, particularly at temperatures above 16°C.
 Microbes can enter milk via the cow, air, feedstuffs, milk handling equipment and the
milker.
 Raw milk :
The lacteal secretion , practically free from colostrum, obtained by the complete milking
of one or more healthy cows(PMO).

4.  Water : 87-88% .
 Carbohydrate: (approx. 5%)
• Mainly lactose→ lactic acid by bacterial fermentation.
• In heated milk products, e.g., in condensed milk, there is also lactulose which is a little sweeter.
 Fat: 3-4% in whole milk.
•contains fat soluble vitamins, pigment carotene & Xanthophylls; contains cholesterol &
phospholipids but is primarily TGs(95%) .
• The fat in milk occurs in the form of droplets or globules, surrounded by a membrane
and emulsified in the milk serum part.
COMPOSITION OF MILK

5. COMPOSITION OF MILK
 Protein: (3-4%).
 Casein (80% of milk protein):
 The casein is arranged in super-structures called micelles, which consist of
protein together with phosphate, citrate and calcium.
The caseins are actually a group of similar proteins, which can be separated
from the other milk proteins by acidification to a pH of 4.6 .
The casein micelles also may be coagulated by addition of the enzyme
rennin.

6. COMPOSITION OF MILK
 Vitamins & Minerals:
 Vitamins A, B6, B12, C, D, K, E, thiamine, niacin, biotin, riboflavin.
 Vitamin A is naturally in the fat component of whole milk.
 whole milk is generally (98%) fortified with vitamin D because it is naturally present only
in small amounts.
 Minerals:
 Ca & P approx. 1% of milk
 Ca is present as calcium caseinate, calcium phosphate & calcium citrate.
 Other minerals present are chloride, magnesium, potassium, sodium, and sulfur.

7. CONTAMINATION OF MILK AND
MILK PRODUCTS
 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.

8. FEW TYPES OF MICRO ORGANISMS
FOUND IN MILK

9. PHYSICAL PROPERTIES
 Acidity: fresh milk pH is 6.5-6.7 at 25°C.
 Viscosity: depends on the amount of fat, size of fat
globules & extent of clustering of globules
 Freezing point: -0.55°C addition of 1% of water to milk
↓ FP by -0.0055°C.
 Boiling point: 100.2°C.

10. Pasteurized milk is raw milk that has been heated to a
specified temperature and time to kill pathogens that may be
found in the raw milk.
 Pasteurized milk can store for short time.
 Only eliminate pathogenic micro-organisms.
 For pasteurization only heat is used.
PASTEURIZATION OF MILK

11. PATHOGENS
A pathogen or infectious agent is a biological agent that
causes disease or illness to its host. The term is most often
used for agents that disrupt the normal physiology of a
multicellular animal.
 A bacterium, virus, or other microorganism that can
cause disease.

12. HISTORY OF PASTEURIZATION
 Pasteurization term is first time used by Louis
Pasteur in 20 April 1862,and eliminate bacteria
in wines
 The pasteurization of milk was adopted in
1895.

13. PASTEURIZATION OF MILK
 Methods:
1. High-Temperature Short Time (HTST)
Pasteurization
2. Low-Temperature Long Time (LTLT)
pasteurization
3. Ultra High Temperature (UHT) Pasteurization

14. (1) HIGH-TEMPERATURE SHORT
TIME (HTST) PASTEURIZATION
 This type of pasteurization is also known as flash
pasteurization.
 High temperature short time. This method is know as
continuous process of pasteurization and is 72C for 15 sec .
 This will ensure that the milk is heated uniformly to the
required temperature.

15. HIGH-TEMPERATURE SHORT
TIME (HTST) PASTEURIZATION
 This method is most suitable in continuous pasteurization
systems.
 Flash pasteurized milk will keep for between 16 and 21
days. For commercial reasons, some manufacturers
intentionally reduce the number of days to push the products
out of the shelves.

16. (2) LOW-TEMPERATURE LONG
TIME (LTLT)
 Low temperature long time this method commonly know as
Batch or Holding method of pasteurization and ideal
temperature is 63C for 30 minute(Milk)
 This method is best for batch pasteurization where the milk
is held in a jacketed vat for effective pasteurization.
 There are many designs of batch pasteurizers in the market
that are suitable for both domestic and commercial use.

17. (3) ULTRA HIGH TEMPERATURE
(UHT) PASTEURIZATION
 This process was developed in 1950.and temperature
are provide 135C to 150 C for one second.
 Despite the risk of Millard browning, UHT
pasteurization remains the most popular milk
preservation method for safe and stable milk.

19.  Milk chilling
 Pre-heating and
Standardization Stage
 Clarification stage
 Standardization stage
 Homogenization stage
 Heating section
 Holding section
 Cooling/chilling section
STEPS OF PASTEURIZATION

20. PURPOSE OF PASTEURIZATION
 To increase milk safety for the consumer by destroying
disease causing microorganisms (pathogens) that may be
present in milk.
 To increase keeping the quality of milk products.
 To reduce the bacterial population in milk.

21. STERILIZATION OF MILK
Sterilization is a process of killing all microorganisms in Milk.
 Commercially sterilized milk:
 It is cooked to an even higher temperature for a shorter
amount of time.
 Commercially sterile milk can safely remain on the shelf
for months, and does not need to be refrigerated until
opened. e.g ultra pasteurized milk.

22. STERILIZATION OF MILK
 Virtually sterile:
 Milk is virtually sterile when it is synthesized in a healthy cow's
udder (mammary gland). Many of these bacteria are not harmful to
humans, but some may be harmful to humans even though the
cows are not affected and appear healthy.
 Milk may become contaminated with bacteria during or after
milking.

23. STERILIZATION PROCESS
The sterilization process in the canned product can be subdivided
into three phases:
 Phase 1 :(heating phase) the product temperature is increased
from ambient to the required sterilization temperature.
 Phase 2 :(holding phase) This temperature is maintained for a
defined time.
 Phase 3 :(cooling phase) the temperature in the can is decreased
by introduction of cold water.

24. METHODS OF STERILIZATION
Classification of Sterilization
Physical methods Chemical methods.

25.  Sunlight
 Drying
 Heat:
 Dry heat:
flaming, incineration, hot air .
 Moist heat:
pasteurization, boiling, steam under
pressure.
 Filtration:
candles, asbestos pads,
membranes.
 Radiation
 Ultrasonic and sonic
vibrations.
PHYSICAL METHOD OF STERILIZATION
These are physical agents which are used for sterilization:

26.  Alcohol
 Ethyl, isopropyl,
 Aldehydes
 Formaldehyde, glutaraldehyde
 Dyes
 Halogens
 Phenols
 Gases:
Ethylene oxide, formaldehyde,
beta propiolactone.
CHEMICAL METHOD OF
STERILIZATION
These are chemical agents which are used for sterilization:

27. GENERALLY USED STERILIZATION
METHODS IN LABORATORY
 Dry heat :
 Glassware and plastic ware (empty vessels), and instruments
may be sterilized by dry heat in an oven at 160-180 C for 3 hr.
 But most people prefer to autoclave.
 More recently, glass bead sterilizers are being employed for
the sterilization of forceps, scalpels, etc.; These devices use dry
heat.

28. GENERALLY USED STERILIZATION
METHODS IN LABORATORY
Flame sterilization :
Instruments like forceps, scalpels, needles, etc.
Are ordinarily flame sterilized by dipping them in
95% alcohol followed by flaming.
These instruments are repeatedly sterilized during
the operation to avoid contamination.

29. GENERALLY USED STERILIZATION
METHODS IN LABORATORY
 Autoclaving :
 Like as Culture vessels are generally sterilized by heating in
an autoclave or a pressure cooker to 121C at 15P for 15 to 40
minutes.
 Sterilization during autoclaving depends mainly on
temperature.
 Certain types of plasticware and some instrument, e.g,
Micropipettes, etc., Are also autoclavable.

30. ADVANTAGES OF STERILIZATION
No significance rise in temperature.
Continuous process due to short exposure time.
Distinction rich flavor.
Economical to use.
Easy control of lethality of various materials and
supplies.

31. DISADVANTAGE OF STERILIZATION
Increased cost of production.
May lead to color change.
Sterilization depreciates milk’s nutritional value.
Packaging of UHT milk is non-biodegradable.
UHT process alters milk’s original flavor.

32.  Products have shorter
shelf life.
 Discovered by Louis
Pasteur.
 Eliminate only pathogenic
bacteria.
 Products have longer shelf
life.
 Discovered by Nicolas
Appert
 Eliminate All form of micro
organisms.
DIFFERENCE
Pasteurization: Sterilization:

33. NON-FERMENTED PRODUCTS
 Skim milk:
When all the milk fat is removed from
whole milk. Extensive use in bakery &
confectionery. Also used for low calorie diets &
children who need high protein.
 Evaporated milk:
Made up of cow’s milk & has thick creamy
appearance.Un sweetened condensed milk ,cow
milk product where about 60% of water
removed from fresh milk.

34. NON-FERMENTED PRODUCTS
 Sweetened condensed milk:
It is made by removing most
of water from cow’s milk . It
is sweeter have high calories
then evaporated milk.

35. A LACTOSE-FREE MILK:
It is available for people who are
lactose-intolerant. This modified milk
is made by filtering regular milk to
remove half the lactose. The enzmye
lactase is then added to the milk to
break down the remaining lactose into
simpler forms which the body can
absorb.
NON-FERMENTED PRODUCTS

36. NON-FERMENTED PRODUCTS
 Malted Milk : is a powdered gruel made from a mixture of malted
barley, wheat flour, and whole milk, which is evaporated until it forms a
powder.
 Malt powder comes in two forms:
 Diastatic malt contains enzymes that break down starch into
sugar; this is the form bakers add to bread dough to help the
dough rise and create a good crust.
 Nondiastatic malt has no active enzymes and is used
primarily for flavor, mostly in beverages. It sometimes
contains sugar, coloring agents, and other additives.

37. Rabri: concentrated sweetened product
comprising several layers of clotted cream.
Sugar is added to milk reduced to 1/3 of its
original volume.
Ice-cream: frozen dairy product
consisting of whole milk, skim milk, cream,
butter, condensed milk products or dried milk
products.
NON-FERMENTED PRODUCTS

38. CREAM:
Cream is the high-fat component separated
from whole milk as a result of the creaming
process. It has a higher proportion of fat
droplets to milk than regular fluid milk; and
according to federal standards of identity,
cream must contain 18% milk fat or more.
Due to this high fat content of cream
compared to milk, some yellow, fat- soluble
pigments may be apparent.
NON-FERMENTED PRODUCTS

39. FERMENTED MILK PRODUCTS
Butter:
It id dairy product made fromm the fat & protien components of
milk or cream.
 fat content is generally about 80%.
 Made from sweet or sour cream.
 Butter may have a yellow color due to the fat-soluble animal
pigment, carotene, or an additive.

40.  Ghee: a type of clarified butter, is prepared by
simmering butter and removing the residue.
The texture, colour, and taste of ghee depend on
the quality of the butter and the duration of the
boiling.
 Buttermilk: was the liquid left behind after
churning butter out of cream. It is beneficial to
health as it contains probiotic microbes.
FERMENTED MILK PRODUCTS

41. FERMENTED MILK PRODUCTS
 Yogurt is a variety of curd. Whole, low fat, skim milks & even
cream can be used to make yogurt.
 In production of yogurt, a mixed culture of streptococcus
thermophilus, lactobacillus acidophilus is usually added to to the
pasteurised milk & incubated.
 Increase in folic acid concentration during
fermentation.

42. FERMENTED MILK PRODUCTS
Fermented milk is useful for a wide variety of
disorders like colitis, constipation, diarrhoea,
gastroenteritis, diabetes & hyper cholesteremia.
Shrikhand: fermented product made by
concentrating dahi by removing whey & to which
sugar,
flavor & condiments are added.

43.  Flavour
 Texture
 Type of milk
 Type of bacteria & mould
species used in ripening,
 Salts & seasoning added
 Manufacturing & processing
method..
FERMENTED MILK PRODUCTS
 Cheese is made up of casein. Varieties of cheese are differentiated
according to their :

44. REFERENCES
 Srilaksmi.B, Food Science, Third Edition, 2003, New Age
International Publisher, New Delhi.
 Vaclavik,V.A., Christian,E.W., Essentials of Food Science,
Third Edition, Springer.
 Journal of food science & technology.
 http://www.ifst.org/learninghome/.

45. AlfahadFarwa - Teacher College in jatoi (business.site)