CHAPTER 1. MILK HYGIENE.ppt from production to consumption

The chapter describes the hygiene of milk. The chapter contains both theoretical and practical concepts

1. CHAPTER 1. MILK HYGIENE
By Endrias Zewdu
Gebremedhin (DVM,
Dip, MSc, PhD, DVSc,
Professor of Veterinary
Public Health
1

2. CHAPTER CONTENTS
Objectives
Milk synthesis
Constituents of milk
Factors influencing composition of milk
Physico-chemical properties of milk
Criteria for raw fresh milk
Milk Quality Assessment
Standards of raw milk
Problems with milk
Tests on heat-treated milk
2

3. CHAPTER CONTENTS…
Sources of milkborne diseases
Contamination of milk
Drug residue test in food
Mastitis: Economic significance, effects on the
quality of milk and milk products
Sanitation in farm and in dairy processing
industries
Milk preservation: pasteurization, Sterilization,
upperisation, the lacto peroxidase-thiocianite
hydrogen peroxide system
3

4.  
MILK HYGIENE
Objectives
Provide consumers with wholesome milk
Safeguard the public from milk-borne zoonotic
diseases and residues
Advise dairymen, creameries and consumer on
the proper handling of milk and milk products
Reduce economic losses resulting from milk
spoilage
4

5. MILK SYNTHESIS
Milk, especially bovine milk, is an important source of essential
nutrients in human diet
Milk protein (MP) can provide essential amino acids (EAAs) and
has high nutritional value
 Amino acids (AAs) are the building blocks of protein synthesis;
they also suppress protein catabolism and serve as substrates for
gluconeogenesis
Most MPs are mammary-derived, synthesized within mammary
epithelial cells (MECs)
 Mammary-derived MPs consist of casein and whey proteins
Casein accounts for approximately 80% of the MPs in dairy
cows
5

6. MILK SYNTHESIS…
Mammary-derived MPs are synthesized using substrates extracted
from blood as free AAs (FAAs) and peptide-bound AAs (PBAAs).
Milk synthesis in the udder of a cow is a complex biological process
that Udder of cow: four separate compartments or quarters, each
with its own milk-producing tissue.
MP synthesis and secretion involve integrated steps such as FAA and
PBAA uptake, transcription and translation of MP genes, proteins
modification after translation, and finally, secretion of the proteins
into the alveolar lumen
Milk synthesis
uptake of nutrients-CHO, Proteins, Fat,
absorbed into the bloodstream and transported to the mammary
gland
serve as building blocks for milk production
6

7. MILK SYNTHESIS…
Alveoli in udder- responsible for milk synthesis
Alveoli are surrounded by tiny blood vessels, which
deliver the necessary nutrients and hormones required
for milk production.
The milk components are synthesized within the cells,
mainly by the endoplasmic reticulum (ER) and its
attached ribosomes.
The energy for the ER is supplied by the mitochondria.
 The components are then passed along to the Golgi
apparatus, which is responsible for their eventual
movement out of the cell in the form of vesicles
7

8. 8
Diagrams of the Udder Quarter, Alveolus, and Secretory Cell

9. MILK SYNTHESIS…
Milk synthesis is regulated by the hormone prolactin, which is
released from the pituitary gland in response to suckling or milking
stimulation
Prolactin acts on the mammary epithelial cells, stimulating them to
synthesize milk components.
Additionally, other hormones such as growth hormone, insulin, and
cortisol play roles in regulating milk synthesis.
The mammary epithelial cells take up nutrients from the blood,
including glucose, amino acids, and fatty acids and then converted
into milk.
Glucose is used as an energy source for milk synthesis, while amino
acids are utilized to produce milk proteins such as casein and whey
proteins.
 Fatty acids are incorporated into milk fat, which gives milk its
characteristic richness.
9

10. MILK SYNTHESIS…
The synthesized milk components are then transported
into the alveoli's lumens and subsequently into the milk
ducts, where they mix and form milk.
The milk is stored in the udder until it is released
through milking
Milk synthesis is influenced by
the cow's nutritional status, lactation stage, and
milking frequency
The composition of milk can vary depending on
factors like breed, diet, and stage of lactation.
10

11. MILK SYNTHESIS…
The release of milk is triggered by the hormone
oxytocin, which is released in response to
stimulation of the cow's udder, such as suckling
or milking.
Oxytocin causes the contraction of
myoepithelial cells, leading to the expulsion of
milk from the alveoli into the milk ducts
Milk quality is influenced by hygiene, cow
health, genetics, and nutrition.
11

12. 12
Constituents of Milk
speciesFat
%
Protein
%
Lactose
%
Human 4, 38 1, 23 6, 94
Cow 3,5- 4,53, 25 4, 7
Goat 4, 5 3, 3 4, 4
Ewe 7, 5 5, 6 4, 4
Camel 3, 1 4 5, 6

13. 13
Constituents of Milk
Milk
Total solids Water
Fat Solid not fat
(SNF)
True fat Associated substances
Carotene Cholestrol
Lactose
Fat
Protein

14. FACTORS INFLUENCING COMPOSITION OF MILK
1.Species: e.g. cow's milk, goat's milk, and sheep's milk have
different compositions.
2. Breed: different breeds of cows can yield milk with varying fat
and protein content.
3. Stage of lactation: The composition of milk changes throughout
the lactation period. In the early stages, milk contains higher levels
of proteins and minerals, while later stages may have higher fat
content.
4. Individual variations: age, diet, and overall health can impact
the composition of milk produced by an individual animal
5. Diet: The diet of the animal plays a crucial role in determining
milk composition. The type and quality of feed, as well as the
presence of specific nutrients, can affect the levels of proteins, fats,
carbohydrates, vitamins, and minerals in the milk.
14

15. FACTORS INFLUENCING COMPOSITION OF MILK…
6. Environmental factors: Environmental conditions, such as climate,
temperature, and geographical location, can indirectly influence
milk composition by affecting the availability and quality of the
animal's feed.
7. Management practices: How the animals are managed,
including their housing conditions, hygiene, milking practices, and
overall animal welfare, can have an impact on milk composition.
8.Genetic factors: Genetic selection and breeding programs can
be used to enhance specific traits in animals, including milk
composition. Selective breeding can lead to animals that produce
milk with desired characteristics, such as higher protein or fat
content.
9. Health and disease: Certain diseases or infections can alter the
composition of milk and may even render it unfit for consumption.
15

16. PHYSICO-CHEMICAL PROPERTIES OF MILK
Acidity & pH
 Density & specific gravity
 Colour
 Flavour
 Viscosity
Specific heat
 Electrical conductivity
 Oxidation-reduction potential
 Boiling point
 Freezing point
The physical and chemical
properties play a crucial role
in determining the quality,
processing, and utilization of
milk.
Viscosity: Milk exhibits a
certain degree of viscosity,
which refers to its resistance to
flow. Viscosity is influenced by
factors such as fat content,
temperature, and the presence
of proteins. Higher fat content
tends to increase viscosity.
16

17. IMPORTANCE OF PROPERTIES
Helps in detection of adulteration.
Helps in determining quality of milk.
Helps in processing of milk & milk products.
Helps in evaluating physical changes in milk &
milk products during processing
17

18. 1. PHYSICAL STATE OF MILK
In milk water is present as continuous phase in
which other constituents are either dissolved or
suspended.
Lactose and Portion of mineral salts form Solution.
Protein and Remainder of minerals form Colloidal
Fat forms Emulsion.
18

19. 2. ACIDITY OF MILK
Freshly drawn milk is amphoteric to litmus i.e. It turns red
litmus blue and vice versa.
 However milk shows a certain acidity as determined by
Titration with an alkali (NaoH) in presence of an
indicator (phenolphthalein)
 This acidity is known as titratable acidity (T.A.).
Natural or apparent acidity (N.A.)-due to presence of
casein, acid- phosphates, citrates etc. in milk.
The higher the SNF content of milk higher is the N.A. of
milk and vice versa.
T.A. of cow milk varies from 0.13-0.14 %.

19

20. 2. ACIDITY OF MILK…
Developed or Real acidity: due to lactic acid
formed in the milk as a result of bacterial action
on lactose in the milk.
Titrable acidity= N.A.+ developed acidity
20

21. 3. PH OF MILK
The pH of milk usually falls within the range of
6.4 to 6.8.
pH is a measure of acidity or alkalinity, and
variations outside this range can affect the
stability and shelf life of milk
Higher pH values indicate udder infection
(mastitis)
While lower pH values indicate bacterial
action.
21

22. 4.DENSITY AND SPECIFIC GRAVITY
 Density measurements can provide information about milk
adulteration or dilution.
D = mass/ volume
Sp.gr= density of substance/ density of water
The density or sp.gr. of milk may be determined by Pycnometer or
Hydrometer or Lactometer.
Milk is heavier than water.
Av. Sp.gr. of cow milk (60 F) = 1.028 to 1.030
The sp gr. of milk is lowered by addition of water
Fat/cream content reduces the specific gravity since fat is the lighter portion
SP.gr. Is increased by addition of skim milk or removal of fat.
22

23. 5. FREEZING POINT OF MILK
Milk freezes at temperature slightly lower than
water due to presence of soluble constituents.
Average freezing point of cow milk= 0.54 C
Lowering of freezing point indicates addition of
water.
23

24. 6. COLOUR OF MILK
The color of milk can vary slightly, ranging from white
to slightly yellowish, depending on factors such as
breed, diet, and the presence of certain pigments.
However, significant changes in color may indicate
quality issues.
Casein , fat globules and carotene.
Buffalo milk = white
Cow milk= light yellow
Skim milk = light bluish
Whey = greenish yellow
24

25. CRITERIA FOR FRESH RAW MILK
Free from pathogens and residues
Natural composition
Temperature is 10 degree
Specific gravity is between 1. 028 - 1. 030
pH 6. 7
Sensoric quality unchanged ( taste, odor, appearance,
consistency)
Total bacterial and cell count each 300,000 / ml of milk
25

26. MILK QUALITY ASSESSMENT
Reception testing
Organoleptic test: taste, smell, visual observation
and temperature
Cheap, quick and does not require any equipment
Test Performed in the Laboratory
1. Adulteration tests
Lactometer reading: combine the lactometer reading with the
fat test
Low fat but high density- indicate milk is skimmed
Low fat and low density indicate milk is adulterated- water
added
In the lab Conductivity test, Freezing point, and determination
of fat content
26

27. DETERMINING ITS FRESHNESS
Determination of pH
Titratable acidity
Methylene blue reduction test
Resazurin test
Alcohol test
Clot on boiling
quick and cheap
5 ml of milk flamed for 4 min
Sour and abnormal milk (mastitis) will not pass this
test
Reject if the milk clots
27

28. 2. Alcohol test
Sour, colostrum or mastitis milk will not pass
Mix equal amounts (2 ml) of milk and a 68% ethanol
solution
Milk that contains more than 0.21% acid will coagulate
when alcohol is added
3. Acidity test
Measures the lactic acid in the milk
If the acidity is higher than 0.19%, then the milk quality
is poor and cannot be processed
If the acidity is lower than normal (e.g. 0.10% lactic
acid) then the milk is of poor bacterial quality –
NaHCO3 or NaOH added
28

29. 5. Gerber test for fat
Used to determine the fat content of the milk
 10.94 ml. of milk at 20
o
C is added to a
butyrometer together with sulphuric acid and amyl
alcohol
Centrifuge and put the sample at 65
o
C water bath
Read after 3 minutes
The fat content from this reading should not be less
than 3%
 
29

30. STANDARDS OF RAW MILK
No water is allowed to be added
Antibiotic residue must not exceed specified level in
legislation
Residues shall not exceed permitted tolerance limits
Bacterial counts: ≤at 10
5
cfu/ml raw cow milk for heat
treatment i.e. drinking or flavoured milk
Bacterial counts: ≤at 4X10
5
cfu/ml for raw cow milk or
other milk products
Somatic cell count at or below 4X10
5
for heat treated
milk i.e. drinking
Somatic cell count at or below 5X10
5
for other milk
products
High counts indicate inflamed udders
30

31.  PROBLEMS WITH MILK
Blood (mastitis)
Leucocytes (increases in number in mastic cows)
Milk taint from certain medicines, feed (kale, turnip),
illness (mastitis), uncovered milk near smell
Milkstone – phosphate and albumen deposits when milk
heated over 72
o
C- problem in cleaning
Food poisoning due to raw milk reflects inherently unsafe
nature of production
Food poisoning following pasteurisation results from
failure of control which can be related to poor plant
design and maintenance and inadequate operator
training
31

32. DEFECTS ENCOUNTERED IN RAW MILK
32
Flavour defects cause
Rancid Fat hydrolysis, increased lipase
activity
Barny Poor ventilation
Bitter weeds
Wet dog Contamination with E. coli
Cheesy Increased activity of protelytic Mo.
sour acid development

33. SOURCES OF MILK-BORNE DISEASES
 
A. The cow
B. The milk handlers
C. The milk containers- contact surfaces
D. The milking and milk-handling environment
Milk borne Diseases :
Tuberculosis- Q fever
Brucellosis - Listeriosis
Salmonellosis -E. coli infection
Mycotoxicosis - S. aureus
Allergy, lactose intolerance
33

34. SOME OF THE MAIN REASONS WHY MILK IS AN IMPORTANT
TRANSMITTER OF DISEASES TO HUMAN ARE:
 
1. Milk is a relatively good medium for m/os to
grow
2. Milk is easily contaminated during its production.
3. Milk is delicate and easily spoiled if not handled
and maintained under hygienic conditions.
4. Milk is most likely to be consumed raw or without
treatment
5. Milk is usually part of the normal diet of the most
vulnerable groups of the population – infants, the
elderly, convalescents, etc.
34

35. CONTAMINATION OF MILK
Microbial and non-contamination of milk: two types of
potential hazards that can affect the quality and safety
of milk.
After secretion from udder, milk can be immediately
contaminated by spoilage bacteria and pathogens from
various sources, including
Animal faeces, FLIES
Soil
Air
Feed
Water
Bedding material
Animal hide
Infected udder
The exterior of udder and teats
Milk containers and
People
35

36. CONTAMINATION OF MILK…
Common types of microbial contaminants in milk include
Escherichia coli (E. coli), Salmonella, Listeria
monocytogenes, and various spoilage bacteria.
Consuming milk contaminated with these
microorganisms can lead to foodborne illnesses and
pose a risk to human health
Non-microbial contamination:
Refers to the presence of unwanted substances in milk that
are not microorganisms.
These contaminants can originate from various sources, such as
environmental pollution, improper storage, or inadequate
cleaning of milk processing equipment
36

37. BACTERIA
LAB= Lactic acid bacteria
Gram -ve Gram +e
LAB
None spore
formers
spore
formersColifrms
Citrobacter
Serratia
Proteus
Escherichia
Klebisella
Hafenia
Micrococcus
Brochotrix
Bacillus
Clostridia
Lactobacillus
Streptococcus/
lactococcus
Leuconstoc
Pedicoccus
Bacteria
37

38. CONTAMINATION OF MILK…
E.g. of non-microbial milk contamination
Pesticides, antibiotics, heavy metals, mycotoxins, and cleaning
agents.
These substances can contaminate milk during production,
transportation, or processing, and their presence can pose health
risks if consumed in significant quantities.
To ensure the safety and quality of milk:
 Strict hygiene practices
 Proper sanitation of equipment
 Adherence to regulatory standards are essential
Regular testing and monitoring of milk for microbial and non-
microbial contaminants are crucial steps in maintaining the
integrity of milk and protecting consumer health.
38

39. DRUG RESIDUAL TEST IN FOOD
This tests are typically performed by regulatory bodies,
food safety agencies, or quality control laboratories to
ensure compliance with food safety standards
This test is conducted to ensure the safety and quality of
milk products for human consumption
Enzyme-linked immunosorbent assay (ELISA). ELISA is a
sensitive and specific technique that uses antibodies to
detect and quantify the presence of drugs or their
metabolites in a sample.
The milk sample is mixed with specific antibodies that
bind to the targeted drug or its metabolite.
39

40. DRUG RESIDUAL TEST IN FOOD …
 If the drug is present in the sample, it will bind to the antibodies,
forming an antigen-antibody complex.
This complex can be detected and measured using colorimetric or
fluorescent signals.
Liquid chromatography-mass spectrometry (LC-MS) and gas
chromatography-mass spectrometry (GC-MS)
These methods offer high sensitivity and specificity and are
capable of identifying a wide range of drugs and their
metabolites
Common drugs of concern in milk include antibiotics, such as
penicillin and tetracycline, and veterinary drugs, such as
antiparasitic agents
For milk to be acceptable for consumers the level should be
below the acceptable limits established by regulatory agencies
40

41. MASTITIS: ECONOMIC SIGNIFICANCE, EFFECTS
ON THE QUALITY OF MILK AND MILK PRODUCTS.
 Mastitis is inflammation of the mammary gland and udder tissue
characterized by physical, chemical and microbiological changes in milk and
by pathological changes in the udder
It destroys milk synthesizing cells and tissue -permanently
Mastitis is recognized as one of the most costly diseases affecting dairy cows,
worldwide.
Mastitis is the most important reason for the culling of cows and a major cause
of economic loss in the dairy industry.
Two main forms: clinical and sub-clinical mastitis
Every year on average 15-20% of cows are affected in major milk producing
areas of Ethiopia
Less attention is given towards control of mastitis in Ethiopia
41

42. ECONOMIC SIGNIFICANCE
Reduction in the level of marketable milk (estimates have shown a
30% reduction in productivity per affected quarter & a 15%
reduction in production per cow lactation)
Reduction in (perceived or actual) output quality (milk), discarded
milk
Waste or higher use of inputs (labor, feed, drugs, vet service, lab,
Resource cost associated with the disease prevention and control
Human health costs associated with zoonoses or disease control
Negative animal welfare impacts associated with disease
Trade restrictions
Culling of animals at unacceptable age (loss of animals and
replacements are expensive
Fatality
42

43. EFFECT OF MASTITIS ON MILK QUALITY AND COMPOSITION
43
Increases somatic cell count and polymorph
nuclear neutrophils
Decreased lactose, casein and fat production
Increasing blood components like Na, K, Cl,
bicarbonate, IgG, and serum albumin
Electrical potential disrupted
Bacteria, blood cells and enzymes (proteolysis)
Lipolysis and globule breakdown (off flavor)

44. 44

45. EFFECT OF MASTITIS ON MILK QUALITY
M
A
S
T
I
T
I
S
Milk
composition
P
R
O
P
E
R
T
Y
Protein
Fat
Acidity
Heat stability
Sourness
Shelflife
Cheese
Butter

46. SANITATION IN FARM AND IN DAIRY
PROCESSING INDUSTRIES
Introduction
Milk provides an excellent media for the growth of
microbes, so the residue form it can affect the keeping
quality of the milk
Thus detergents and sanitizers are used for this
purposes
Cleaning and sanitation are complementary process
46

47. WHY CLEANING AND SANITATION
Cleaning and sanitation of food establishments are
important for the following reasons:


To prevent food poisoning resulting from cross
contamination between food contact surfaces and food.


To minimize food wastage due to food
contamination.


To ensure cleanliness of premises at all times and
create a more pleasant work environment.
47

48.  Cleaning- cleaning or washing of dairy equipment’s is removal
of soil (milk/milk residue/foreign matter) from the surface of
equipment
Sanitization- it is destruction of all pathogenic and almost all
nonpathogenic microorganisms from the surface of the
equipment. Done by heat or chemicals
Detergent- substances used for cleaning or washing compound
 Sanitizer – substances capable for destroying all pathogenic
and almost all non-pathogenic microbes
Detergents:
Alkali detergents- sodium bicarbonate, sodium hydroxide,
Acid detergents- 1% nitric acid, 7% phosphoric acid,
tartaric acid, gluconic acid
Sanitizers: chlorine, iodine, quaternary ammonium compounds
48

49. 49
Levels of “CLEAN”
Cleaning: Removal of Visible physical dirt and stains
Disinfection: Removal of harmful bacteria / microbes
Sanitation: Process in which most or nearly all micro organisms
(whether or not pathogenic)
Sterilization: Total Germ Kill live (including spores)

50. WHY ARE CLEANING AND SANITIZING
IMPORTANT?

Cleaning and sanitizing are important to food safety
as many food poisoning cases are associated with
inadequate and ineffective sanitation.
Generally, surfaces of equipment, food preparation
tables and utensils that come into direct contact with
food should be washed, sanitized and air-dried.
Sanitation is one of the most important aspects of
operating any food processing facility.
Poor sanitation can have an adverse effect on
product safety and can result in poor product quality.
50

51. Milk preservation: pasteurization,
Sterilization, upperisation, the lacto
peroxidase-thiocianite hydrogen
peroxide system
51

52. OBJECTIVES
 to safeguard the public health i.e to
prevent milk-borne diseases e.g Brucellosis and
Tuberculosis.
 to prolong the shelf life of milk and milk
products.
 to minimise economic losses resulting from
milk spoilage.

53. METHODS
3 methods of pasteurisation
(a) Low temperature long time (LTLT) technique,
(b) High temperature short time (HTST) technique.
(c) ultra pasteurization: 137.8
0
C for at least 2 sec

54. PASTEURISATION
(a) Low temperature long time (LTLT) technique,
milk is heated at 63
0
C and held at such temperature
at least for 30 minutes and cooled to 15
0
C.
(b) High temperature short time (HTST) technique,
milk is heated at 72
0
C and held at this temperature
for 40 seconds or less and immediately cooled it to
15
0
C.
(c)Ultra pasteurization: 137.8
0
C for at least 2 sec

55. UPERISATION
In addition to the above methods, milk could also be heated by
uperisation technique to 150
0
C by direct heat for fractions of a
second

56. ADVANTAGES OF UPERISATION
Prolongs the shelf life of milk
Removes unpleasant flavour
Homogenises the fat
Reduces milk acidity
 Destroys micro-organisms efficiently.

57. PASTEURISATION MAY BE SUPPLEMENTED BY
1. Refrigeration
2. Addition of preservatives such as
boric acid, benzoic acid, salycilic
acid, and hydrogen peroxide.

58. FACTORS INFLUENCING PASTEURISATION
Temperature
Holding time
Bacterial load
Duration of heat application
Proper functioning of the pasteuriser

59. ADVANTAGES OF PASTEURISATION

Reduces bacterial load
Kills pathogenic and vegetative micro –organisms
Prolongs the shelf life of milk

60. MICROORGANSIMS RESISTING PASTEURISATION

Enteroccocus
 Streptococcus themophilus,
Lactobacillus lactis
Lactobacillus bulgaricus
 Bacillus cerus
Bacillus subtlis
 Bacillus coagulans
 Clostridia.

61. DISADVANTAGES OF PASTEURISATION
Some consumers oppose the
pasteurisation of milk:
Alters the natural taste
Denatures protein
Reduces the lycine, essential fatty acid,
and vitamin content of milk
Alters milk lactose

62. TESTS ON HEAT-TREATED/PASTEURIZED MILK
Phosphatase test
Phosphatase is present in raw milk
 Destruction shows that the milk has been adequately
heat-treated
Perioxidase test
Used to detect overheating of high temperature
short time pasteurisation
 Peroxidase is destroyed after 15 sec at 78
o
C
therefore the enzyme should be present in
pasteurised milk
62

63. PHOSPHATASE TEST
Principle
 Raw milk contains the enzyme phosphatase, which
could be destroyed by heat. Its absence in heated milk
suggests proper heat treatment of milk.
The test can indicate faulty processing and
contamination by untreated milk at concentrations of 1
in 500
There are 2 types of phosphatase (enzyme)
(a) acidic and
(b) alkaline phosphatase

64. Acidic phosphatase being heat
stable, is destroyed at 90
0
C, while
alkaline phosphatase is denatured at 72
0

C.
We test for the presence of alkaline
Phosphatase, to detect effective
pasteurisation.

65. PASTEURISATION MAY BE SUPPLEMENTED BY
Refrigeration
Packing milk in micro-organism free container
Addition of preservatives (illegal, not allowed)
o Boric acid
o Benzoic acid
o salycilic acid
o Hydrogen peroxide
o Potassium nitrate

66. LACTOPEROXIDASE /THIOCYANATE/HYDROGEN- PEROXIDE
SYSTEM (LP SYSTEM) OF MILK
Alternative method for preserving milk
Indigenous antibacterial systems with very low dose use of
chemicals
Three components of LP-system
1. Lactoperoxidase enzyme
●Heat stable, found in mammalian issue, saliva, milk
●Very high concentration in milk
2. Thiocyanate (SCN
-
)
●Some thiocyane is present in milk although the level is
variable i.e., 1-15 mg/l (5 ppm on average)
66

67. LACTOPEROXIDASE /THIOCYANATE/HYDROGEN- PEROXIDE SYSTEM (LP
SYSTEM) OF MILK …
3. Hydrogen peroxide (H2O2)
Present in milk is very small concentration
The antibacterial effect of the LP-system is proportional
to the thiocyanate concentration in the milk
The activation of the lactoperoxidase has a bacteriostatic
effect on the raw milk and effectively extends the shelf
life of raw milk for 7–8 hours under ambient
temperatures of around 30°C or longer at lower
temperatures.
This allows adequate time for the milk to be transported
from the collection point to a processing centre without
refrigeration
67

68. LACTOPEROXIDASE /THIOCYANATE/HYDROGEN- PEROXIDE SYSTEM (LP SYSTEM) OF
MILK …
The velocity of this reaction is temperature dependent, i.e. more
rapid at higher temperatures. Pasteurisation of the milk will ensure
a complete removal of any residual concentrations of the active
oxidation products.
Due to the mainly bacteriostatic effect of the system, it is not
possible to disguise poor quality milk, which originally contained a
high bacterial population, by applying this method
The activation of the lactoperoxidase system should be carried out
within 2-3 hours from the time of milking
Effectiveness of LP-s depends on three factors: storage
temperatures of milk, bacterial cell density & type of organism
●LP-s persists only for limited time-period which decreases as the
ambient temperature increases
68

69. LACTOPEROXIDASE /THIOCYANATE/HYDROGEN- PEROXIDE SYSTEM (LP SYSTEM) OF
MILK …
●LP-s relevant to low temperature storage due to the
growth of Pseudomonas spp. & Listeria
monocytogenes
●The efficacy is low at high bacterial concentrations
Antimicrobial activity of LP-s has been demonstrated
against a wide range of microorganisms, e.g., bacteria,
HIV-1 virus, moulds, yeasts, mycoplasma & protozoa
Depending upon the bacterial species or even the strain
of the microorganism the effect can be bacteriostatic or
bactericidal
LAB: sometimes self-inhibitory, Catalase +ve are not
69

70. Health Issues Associates with the use of LP-s
The levels of H2O2 introduced into the milk via
sodium percarbonate is very low and not of
concern
As there is no change to the enzyme
concentrations naturally present in milk, this
component is not considered of toxicological
significance
Thiocyanate interferes with iodine metabolism
and uptake by the thyroid, especially in Iodine
deficient subjects hence a potential goitrogenic
substance
70

71. INTENDED UTILIZATION OF THE METHOD
Intended Utilization of the Method
The method should primarily be used to prevent undue
bacterial multiplication in raw milk during collection and
transportation to the dairy processing plant
This method should only be used in situations when
technical, economical and/or practical reasons do not
allow the use of cooling facilities for maintaining the
quality of raw milk.
Use of the LP-system in areas which currently lack an
adequate infrastructure for collection of liquid milk,
would ensure the production of milk as a safe and
wholesome food, which otherwise would be virtually
impossible.
71

72. The method should not be used by the individual
milk producer but at a suitable collecting
point/centre. These centres must be equipped
with proper facilities for cleaning and sanitizing
the vessels used to hold and transport milk.
Use of LP-s is a reliable & economical method of
preserving raw milk as compared to
refrigeration in small-scale dairy enterprises,
coupled with good hygiene and sanitation.
72

73. PEROXIDASE TEST
 Used to detect overheating of high temperature
short time pasteurisation
 Peroxidase is destroyed after 15 sec at 78
o
C therefore
the enzyme should be present in pasteurised milk
The test is performed to find out, whether milk has been
Heated at 85
0
C and above.
Method
Pour 5 ml milk and 0.5 ml of the reagent ( phenol) into test
tube, mix this thoroughly and put it aside.

74. INTERPRETATION

Red brown color suggests positive
i.e. the milk has been heated at 85
0
C.

If the milk retains its white color it
indicates that the milk has not been heated
at 85
0
C.

75. TURBIDITY TEST (ASCHAFFENBURG TEST)
The phosphatase and peroxidase test do not
differentiate between pasteurised and
sterilised milk, but the Aschafenburg test
will ascertain this

76. METHOD
Put 4 grams of ammonium sulphate into 50 ml flask
Pour 20 ml milk to it
Shake for minutes and set it aside for 5 minutes
Filter the solution and retain it in a test tube
Put 5 ml of the filtrate in another test tube and heat it in
water bath at 100
0
C for 5 minutes.
Cool and examine for the presence of turbidity.

77. INTERPRETATION

Turbidity present - the milk is sterile
Turbidity absent -the milk is not sterile