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1. COMPOSITION OF MILK

2. WHAT IS MILK
 The lacteal secretion, practically free from colostrum,
obtained by the complete milking of one or more healthy
animals.

3. COMPONENTS OF MILK
Milk
Water Total solids
Fat Solids-not-fat
Protein Lactose Minerals Vitamins Enzymes

4. MILK COMPOSITION FROM DIFFERENT SPECIES
Nutrient
(%)
Cow Buffalo Goat Human
Total solids 13.0 16.5 12.3 12.2
Fat 4.0 6.7 4.5 3.8
Protein 3.4 4.5 2.9 1.0
Lactose 4.8 4.8 4.1 7.0
Ash 0.7 0.8 0.8 0.2
 Total solids (TS) = SNF + Fat
Solids-not-fat (SNF)

5. ABNORMAL MILK
Colostrum Mastiitc milk Normal milk
Lactose is less than
normal
Low lactose Lactose is around 4.9%
Casein : WP ratio is
disturbed
Low casein, Casein:
WP ratio is less
Csein:WP ratio is
around 80:20
-
Increase chloride
(> 0.15%)
014 - 0.15%
pH ~ 6.8 pH > 6.8 pH ~ 6.8
Fat is high
Total protein is high
Minerals – high
High amount of
following enzymes
 Catalase
 N-acetyl-β-D-
glucosaminidase,
 Arylesterase
Normal level of
enzymes and other
components
Immunoglobulins ~7% -
Immunoglobulins ~
0.7%

6. MILK - STANDARDS
 Toned milk – 3%, 8.5%
 Double toned milk – 1.5%, 9%
 Skimmed milk - > 0.5%, 8.7%
 Standardized – 4.5%, 8.5%
 Full Cream milk - 6%, 9%
 Recombined Milk - 3%, 8.5%

7. CHEMICAL TESTING OF MILK

8. Chemical parameters for
consideration
Acidity of milk
Clot-on-boiling (COB) test
Alcohol test
Alcohol-alizarine test
Methylene Blue Reduction
(MBR)Test
Antibiotic residues
Platform test

9. Measurement of acidity of milk
• Natural acidity is due to
– Casein, albumin, citrate, phosphates and CO2
• Developed acidity – due to
bacterial growth – lactic acid
• Can be measured by titrating
milk against standard NaOH
using phenolphthalein
indicator
• Lactic acid reacts with NaOH
Acidity = 9 NV/W
 Expressed as % lactic acid

10. Clot-On-Boiling (C.O.B) Test
• Test is generally performed to assess the
suitability of milk for heat processing and also
give an indication of the keeping quality of
milk.
• It provides a rapid method to determine the
developed acidity as the milk with high
developed acidity (more than 0.24% lactic
acid) gets coagulated when heated to boiling
temperature.

11. Alcohol Test
• Test is used for rapid assessment of stability of milk to
processing, particularly for condensing and
sterilization.
• Useful as an indication of the mineral balance of milk
and not so much as an index of developed acidity.
• The test aids in detecting abnormal milk, such as
colostrum, milk from animals in late lactation, milk
from animals suffering from mastitis and milk in which
the mineral balance has been disturbed.
 Ethanol: 68 % by weight or 75% by volume
 5 ml of milk + 5 ml alcohol – check for flakes

12. Alizarin-Alcohol Test
• Based on same principal as alcohol test and the
incorporation of alizarin helps to indicate the
approximate percentage of acidity.
 Alizarin solution: 0.2% in ethanol (68 %)
 5 ml milk + 5 ml of reagent & observe colour and flakes
Parameter Normal milk
Slightly acid
Milk
Acid milk Alkaline Milk
pH 6.6 – 6.7 6.4 – 6.6 6.3 or lower 6.8 or higher
Colour Red brown
Yellowish-
brown
Yellowish Lilac
Appearance
of milk
No
coagulation
no lumps
No coagulation Coagulation*
No
coagulation **

13. Methylene Blue Reduction (M.B.R) Test
• Indirectly estimates the number of bacteria in milk in
terms of time interval required, after starting
incubation, for a dye – milk mixture with a
characteristic blue color to become white.
• Different MBR times permit grouping of samples into
classes
• Method depends on the ability of bacteria in milk, when incubation is
started, to grow and to utilize oxygen dissolved in the mixture, which in
turns lowers the oxidation-reduction potential of the mixture.
• Reduction time is inversely related to the initial
bacterial content of the sample. This test is of
paramount importance in relation to clean milk
production as it indicates the sanitary and
keeping quality of milk during production.

14. Methylene Blue Reduction (M.B.R) Test
MBRT (h) Grade
5 and above Very good
3 and 4 Good
1 and 2 Fair
Half Poor

15. Fat estimation in milk
• Gerber method - Butyrometer
 This is a quick, routine method in common use
and gives results within accuracy of  0.10%
 Fat in milk exist in the form of small spherical
droplets surrounded by a membrane - milk fat
globule membrane.
 Necessary to destroy this membrane and liberate
the fat in liquid form so that it can be measured
volumetrically.

16. Fat estimation in milk
• Gerber method
 Achieved by treating milk with sulphuric acid of
known specific gravity, which dissolves milk
proteins and carbohydrates and releases fat.
 Released fat is separated from the digested
material by adding small amount of isoamyl
alcohol which acts as surfactant.
 Mixture is then centrifuged at 1100 rpm for 4
min and the volume of separated fat is then
read on the graduated stem of the butyrometer
at 65°C.

17. Apparatus for Gerber method
Milk Pipette
Gerber Butyrometer
Gerber centrifuge
Water-bath for butyrometer (65C)

18. Determination of SNF in milk
• Usually checked by Lactometer – a type of density
hydrometer
• Specific gravity of milk is around 1.028 – 1.032
• SNF→ being heavier than water cause increase in sp.gr.
• Fat → being lighter than water cause decrease in sp.gr.
• Removing fat (with small amount of SNF) as cream
→sp.gr. of milk increases.
• Skim milk is heavier than the whole milk
• A milk naturally low in fat have the lower sp.gr. & conversely one
rich in fat have the higher sp.gr. This is because, in normal milk as
the fat increase the SNF also increase simultaneously. The overall
effect is increase in sp. gr. of milk.
• Jersey milk is heavier than HF. milk & buffalo milk is heavier than
cow milk.

19. Determination of SNF (solids-not-fat)
using lactometer
8/19/2022

20. Electronic Milk testing equipments
 Milko-testerTM
 Milko-scan
8/19/2022