This document summarizes the analysis of milk. It begins by defining milk and describing its typical composition, including higher fat content in buffalo milk versus cow milk. It then discusses various types of milk like standardized, whole, reduced-fat, low-fat, and skimmed milk. The document also covers milk contamination, pasteurization, long-life and UHT processed milk, evaporated and condensed milk. It provides methods to analyze milk properties like specific gravity, pH, total solids, fat content, chloride content, and titratable acidity. Finally, it discusses detecting adulterants in milk and bacteriological examination including viable bacterial count and methylene blue reduction tests.

1. Analysis of milk
Presented
by
Y.Narayudu

2. What is milk ?
• Normal mammary gland secretion of female
mammals
• It is the first food for the baby mammaline
Ca.caseinate
RIBOFLAVIN
Carotene&xanthophyl
• Freezing point – 00 C(water) / -0.550C(solids)

3. Composition of milk
Buffalo milk : high fat content (7.44%)
Cow milk : low fat content ( 3.66%)

4. TYPES OF MILK
o Standardized milk: buffalo milk & skimmed milk
( fat -4.5% & SNF is 8.5%)
o Whole milk: 3.25% milk fat & 8.25% milk solids
(50% of its calories 4m fat)
o Reduced-fat milk (2%): This milk contains 2% milk fat
(35% of its calories)
o Low-fat milk (1%): 23% of its calories from fat

5. o Skimmed milk/non-fat milk: NMT 0.5% milk fat 5% of its
calories from fat. Skimmed milk has about half the
calories of whole milk.
630C for 30min
milk 0
72 C For 15sec
o Pasteurized :
kill bacteria(not spores)
o Pasteurized milk will keep fresh for 2-3 days in a fridge
o Unpasteurized - raw or untreated milk
o It is recommended that babies, young children, the
elderly, pregnant women and anyone with an impaired
immune system should avoid drinking unpasteurized
milk.

6. o Long - life - milk pasteurized & homogenized and then
kept at a high temp for destroy bacteria.
odd burnt caramel flavour
stored for 1 week
o UHT( ultra-heat treatment) milk heated at high temp
(1320C / 2700F)
Stored for upto 3 months

7. o Dried Milk: in powdered form.
o Evaporated : homogenized milk with
considerably reduced water content
o Condensed milk :simply evaporated milk to
which sugar has been added to thicken and
sweeten it. It is mainly used for making
desserts and sweets.

8. Cup of milk
146 calories
49% Fat
30% carbhydrates
21% protein

9. IS IT MILK IS CONTAMINATED….?

10. Contamination of milk
THE NATIONAL NEWS(11-1-2012)& BBC:
“68% of Indian milk contaminated’’
diluted with water
sweeteners
Fat
se volume
non-edible solids
glucose and
skimmed milk powder

11. o Addition of water not only reduces the nutritional
value of milk but contaminated water may also
pose health risks
o The presence of detergent "indicates lack of
hygiene and sanitation in the milk handling”

12. Method of analysis of milk

13. Preparation of sample
o
Warm the sample to 37 0 – 40 0 C by transferring it to the
beaker & keep it in a water bath maintained at 400 - 450C
o
Stir slowly for proper homogenisation. Mix sample
thoroughly by pouring back into the bottle, mixing to
dislodge any residual fat sticking to the sides and pour it
back in the beaker.
o
Allow the sample to come to room temperature
(26 0 - 28 0 C) and withdraw immediately for analysis.

14. SPECIFICGRAVITY
o LACTOMETER
o 1.025-1.035 (250C-350C)
o After 12hr of milking rise
0.0013

15. DETERMINATION OF PH
o PH Meter
o Calibrate the PH Meter
o Avg . PH
6.6
o Due to lactic acid

16. Determination of total solid:
o take a weight of crucible.
o weigh 5 g of milk in a crucible
o put a crucible in a water bath until dryness.
o after complete dryness put the crucible in an oven, and
weigh after cooling.
o determination the percent of total solid.
%Of total solid = (wt of crucible +sample) after drying – wt
of crucible/ wt of sample * 100

17. RICHMOND’S Formula For Total Solids :
T=0.25D+1.22F+0.72
For cow milk 0.66
Where,
D = Density
F = % Fat

18. DETERMINATION OF CHLORIDE CONTENT
10 ml milk + 40 ml water
add 10 drops of pot.chromate
Titrate with 0.1 N AgN03
Brick red ppt
1 ml of o.1 N AgN03 equivalent to 3.55mg of Cl-
INDICATIVE OF DISEASED STATE OF ANIMAL

19. TITRABLE ACIDITY
10 ml milk + 1 ml phnolpthalein indicator
Titrate with 0.1N NaOH
1 ml 0.1 N NaOH ≈ 0.009 g of lactic acid

20. Determination of Fat in Milk
Gerber Method:
Principle:
o milk +H2S04 + iso-amyl
alcohol
o permitting dissoln of the
protein and release of fat.
o The tubes are centrifuged
and the fat rising into the
calibrated part of the tube
is measured as percentage
of the fat content of the
milk sample

21. Procedure:
o 10 ml of H2S04 into a butyrometer tube & Mix the milk sample
o Add 1 ml of Amyl alcohol,close with a lock stopper
o shake until homogeneous soln.Keep in a water
bath for 5 min at 65o C
o centrifuge for 4 min. at 1100 rpm.
o Remove the butyrometer tubes and place in water bath for 5
min.at 650C.
o Read the percentage of fat

22. Werner Schmidt Method(by Acid Digestion Method):
PRINCIPLE:
o Milk proteins are digested with conc. HCl
o Liberated fat is extracted with alcohol, ethyl ether &
petroleum ether
o Ethers are evaporated
o Residue left behind is weighed to calculate the fat
content.

23. 10 g milk+10 ml conc.HCl
heat on a Bunsen burner
stir with a glass rod until the contents turn dark brown
cool to room temp
Mojonnier fat extraction flask
10 ml of C2H50H+ 25 ml of ethyl ether
Shake vigorously for 1 min
25 ml of petroleum ether
Shake vigorously for 1 min
Centrifuge Mojonnier flask at about 600 rpm

24. Decant the ether soln
Repeat extraction
Evaporate the solvent
Dry the fat in oven
Weigh

25. Calculation:
100 (W1 - W2)
Fat, percent w/w ---------------------W3
Where
• W1 = Wt in g of contents in the flask before removal of fat.
• W2 = Wt in g of contents in the flask after removal of fat
• W3 = Wt in g of material taken for the test.

26. Detection of Adulterants in Milk

27. Detection of Cane Sugar in Milk
Modified Seliwanoff Method:
PRINCIPLE:
Fructose + resorcinol in HCl
procedure
Procedure:
std for 10 min
milk + conc. HCl
water bath for exactly 1 min
red colour
filter
1 ml filtered milk serum &
5 ml modified resorcinol - HCl reagent
Withdraw the tube &observe the colour
red colour

28. Test for QAC (Detergents)
o To a centrifuge tube add 1 ml milk, 5 ml water, 1 ml EOSIN
soln & 0.2 ml buffer and shake hard for 10 sec.
o Centrifuge for 5 min at 3200 rpm.
o If QAC is present the bottom layer assumes a red or pink
colour.
o Samples containing 1 mg / kg of QAC show a faint pink
o If the colour is deep pink or red, the amt of QAC can be
approx. determined by titration with a std anionic
detergent soln

29. Detection of added Urea in Milk
o 5 ml of milk is mixed with 5 ml of 1.6 % of
p –Dimethyl amino benzaldehyde (DMAB) is
added Distinct yellow colour observed in milk
containing added urea.
o The control (normal milk) shows a slight yellow
colour due to presence of natural urea.
o:

30. Estimation of Urea in Milk
Prepn of standard Curve:
o Pipette 5 ml std solns into 25 ml T.T Add 5 ml
DMAB soln to each.
o Prepare reagent blank of 5 ml buffer and 5 ml
DMAB soln. Shake tubes thoroughly and let
stand for 10min.
o Read a@420 nm

31. Preparation of sample:
o 10 ml of milk sample add 10 ml of Trichloro
acetic acid (TCA) to ppt the proteins and
filtered.
o 5 ml of filtrate + 5 ml of DMAB
o The optical density of the yellow colour is
measured @ 420 nm.
o From standard curve the amount of urea in
milk is calculated.
70 mg per 100 ml (700 ppm)

32. Detection of preservatives

33. Hehner’s Test (HCHO):
2 ml milk in T.T
2 ml of 90 % H2SO4 traces of FeCl3
purple color ring at the junction
Formaldehyde

34. Test for presence of Salicylic acid:
50ml milk + 5 ml of dil.HCl + 50 ml ether
Wash ether layer with water
evaporate ether
1 drop of 0.5 % (v/v) FeCl3
Violet colour

35. Test for presence of H2O2
Milk + conc.HCl
Mix well
drop of HCHO soln
600C
place starch-Iodine paper into soln
oxidesation of iodine
BLUE COLOR

37. Bacteriological Examination of Milk
Normal flora of milk:
oEnterococcus faecalis
oStreptoccus lactus
oLactobacillus sp.
o Candida albicans (yogurt)

38. Determination of viable bacterial count :
The pour plate method:
After preparation of 10 fold serial dilution from
the milk sample with ringer solution

39. Viable Bacterial Count
Using 10 fold serial dilution method
1 ml milk
Milk sample
1 ml
1
1 ml
2
3
9 ml Saline
1/10 x 1/10
1/10
Melted NA
1 ml
1
1/100 x 1/10
1/100
1/1000
1 ml
2
1 ml
3

40. Viable Bacterial Count
Results:
Y
Dilution
factor
No. of colonies per plate
1
2
3
X
X.y
10
x1
X1.y1
102
x2
X2.y2
x3
X3.y3
103
No. of cells per 1 ml =
X1.y1 + X2.y2 + X3.y3
3

41. Results:
o Permissible number of bacterial flora in
pasteurized milk is 5 x 104 cfu/ml
o Permissible number of bacterial flora in long
life milk is 10 cfu/ml

42. Methylene Blue Reduction Test:
determine quality of the milk
o
o
Increasing the number of bacterial flora
will reduce the colour of methylene blue
more rapidly due to increasing consumption
of oxygen.
i.e: The speed of reduction of methylene
blue colour is directly proportional to the
number of bacteria present in milk sample.

43. Results:
The shorter the decolorization time, the higher
the number of bacterial flora present in milk, and
the poor quality of milk
Decolorization time
30 min – 2 hrs
2 – 6 hrs
6 – 8 hrs
Over 8 hrs
Result
Poor quality
fair quality
good quality
excellent quality

44. Test for coliforms:
o
Done by inoculation of MacConkey’s broth with
0.1 ml of milk sample.
o
Examine for the production of acid detected by
changing the color of the medium from purple to
yellow.