The document provides guidelines for sampling milk and milk products including cream, paneer, cheese, khoa, ghee, butter, ice cream, and condensed milk. Some key points discussed include: - Samples should be representative of the entire batch and taken after proper mixing to ensure uniformity. - Different techniques are described for mixing and sampling from individual containers, bulk tanks, and transport vehicles depending on the product. - Precautions like temperature controls and aseptic techniques should be followed to prevent contamination or deterioration of samples.

1. Binod Kumar Bharti
Assistant Professor cum Jr. Scientist
Department of Dairy Chemistry
Sanjay Gandhi Institute of Dairy Technology (BASU) Patna

2. 1. Introduction
2. General requirements while sampling
3. Sampling of Milk
4. Sampling of Cream
5. Sampling of Paneer/Cheese/Chhana
6. Sampling of khoa
7. Sampling of Ghee
8. Sampling of Butter
9. Sampling of Ice Cream
10. Sampling of condensed milk
11. Sampling of Powder

3. ● Proper sampling of milk and milk products is the first step in performing an
accurate chemical analysis of its constituents.
● All errors in chemical and microbiological analysis begins with the sampling
procedure.
● Sampling of milk and milk products is a specific job and shall be done by an
experienced person who is familiar with the techniques and is well acquainted
with the knowledge of the subject.
● Sampling may be required for chemical and bacteriological testing. All
precautions shall be taken to prevent contamination and adulteration.
● It is not possible to lay down a single sampling procedure which will be
applicable in all the cases.
● The method of sampling will vary according to the purpose for which the
sample is collected and the tests which are to be carried out.
● The sample should be taken in random a manner as possible to give each
container or package an equal chance of being selected.

4. ● For chemical examination, the sampling equipment like plunger, sample
bottle, rubber stopper shall be clean and dry.
● For bacteriological examination, all equipments including plunger, sample
bottles and rubber stoppers shall be sterile and the samples shall be collected
under aseptic conditions.
● If subsequent analysis is to be of some value, it is very important that sample
should be a true representative of the bulk.
● Milk fat is of lower density than the other constituents of milk, it has
tendency to rise to the surface.
● Therefore, thorough mixing of milk with a proper instrument which will
reach the entire depth of the liquid is essential to ensure that a representative
samples of the entire batch.

5. ● A sample is the small portion of a product representing the entire batch or lot
of samples.
● The composite sample is the quantity secured by mixing together
proportional parts of different lots of a product.
● There are maximum accuracy in analytical value if the sampling is done
carefully.
● In small batches, it should be possible to accomplish mixing by pouring the
entire quantity of milk from one container to another container, three or four
times.
● Larger batches of milk samples shall be thoroughly agitated by a hand stirrer
or by mechanical process.
● Milk churns easily at temperature between 26.5 to 29.5°C and agitation near
this temperature shall be avoided.

6. ● Sample shall be drawn by an experienced person in a protected
place not exposed to damp, air, bright light, dust, soot or smoke
particles, rain etc.
● The sample temperature while sampling should be between 0 to
15C. If sample is to be transported, the sample temperature should be
maintained between 0-7C (for ice cream - 15C)
● Precautions shall be taken to protect the samples, the material being
samples, the sampling instruments and containers for sample from
adventitious contamination and adulteration.
● The sampling instruments and sample containers shall be clean, dry
and shall not impart any foreign odour, or flavour.

7. ● The sampling appliances used shall be of stainless steel (SS) or of suitable
material and shall be light in weight for the operator to be able to move
them rapidly through the product. All the surfaces of sampling appliances
shall be rounded.
● The sample containers shall be of such size that sufficient head space is
allowed for expansion at the top. At the same time, this space should not be
too large as air exerts detrimental action.
● Each container shall be sealed air tight after filling and marked with full
details of sampling or code number, name and address of manufacturer and
other important consignment.
● Plunger
● Sampling bottle
● Dipper

8. ● The samples shall be sent to the examining laboratory as soon as
possible, and it shall be analysed without delay.
● If not possible, the sample(s) shall be stored in a refrigerated
temperature 0 to 5C, where this is not possible, then adequate
precautions shall be taken to prevent deterioration and exposure to
high temperature and light.
● In some cases, preservative may be added to prevent deterioration
and it does not interfere with the subsequent analysis.
● The preservative added shall be indicated on the label of sample
botles. According to FSSAI (2015), the preservative used in the case
of sample of milk, in liquid form commonly known as “formalin” i.e.
Formalin containing about 40 per cent of formaldehyde in aqueous
solution in proportion of 0.4 ml (two drops) for 100 ml or 100 grams.

9. Milk
● The sample collected for chemical analysis should be representative
of the entire batch of milk that is being sampled.
● Milk fat is of lower density than the other constituents of milk, so it
tends to rise to the surface.
● Through mixing of milk with a proper instrument which will reach
the entire depth of the liquid is essential.
● Milk churns easily at 26.5 to 29.5C and agitation near this
temperature shall be avoided.
● The samples can be preserved with formalin (0.1ml (two drops) for
25 ml of milk), or potassium dichromate (0.06 g/100 ml, for
instrumental methods), or mercuric chloride (0.5g/250 ml milk,
cryoscopic examination) solution.

10. ● Pour the milk from one container to another, three or four times. Where this
is not practicable, mix thoroughly with a plunger.
● In mixing the milk, the plunger shall be allowed to fall to the bottom of the
container and brought to the top of the milk as rapidly as possible not less than
10 times.
● The position of the plunger shall also be moved from place to place to ensure
that the whole of the milk at the bottom of the vessel is thoroughly agitated and
mixed with the upper layer.
● Any milk fat adhering to the neck and under the shoulder of the can shall be
well mixed with the remain of the milk. After thorough mixing, a sample shall
be drawn immediately.

11. ● The sample shall be taken after pouring the contents of the containers into a
vat and mixing it. When this is not possible, a composite sample is taken from
the containers after milk has been agitated and mixed.
The following steps are followed:-
● First, the milk shall be distributed as equally as possible among a number of
containers. The cans shall not be filled, but the same quantity shall be placed in
each.
● After mixing the contents of each can thoroughly, an equal volume of milk
shall be taken from each. These portions shall be placed in another vessel,
thoroughly mixed as described in case of individual container and a sample
then taken.
● A composite sample may be obtained by taking the same proportion of the
milk therein from each container in a consignment after thorough mixing,
collecting this in another vessel and taking a sample as described in case of
individual container.

12. ● The method of sampling of milk from storage tanks/rail/ road tankers is
largely governed by storage/transport conditions.
● In all cases, the milk in the tank and tanker shall be thoroughly mixed by
large plunger, a mechanical agitator; the uniformity of the samples being
determined, when necessary, by mixing till such time as complete agreement is
obtained between samples taken at the manhole and at the outlet cock in respect
of fat and total milk solids.
● When a plunger is used for mixing the milk in rail/road milk tankers, a
satisfactory method is to insert the plunger in the man-hole, the operator sitting
or standing on top of the tanker. The plunger is thrust forward and pulled back,
thrust downwards and pulled back and thrust backwards and pulled back. The
cycle of this operations should be repeated for at least 15 minutes.
● After proper mixing of the milk, the sample should taken from the tank,
removed through the stopcock in the tank door, or from a valve on the
discharge line from the tank when it is being emptied.

13. ● Suppliers of milk are often paid for milk on the basis of milk fat test.
● The determination of fat contents of the suppliers‘ daily deliveries is
laborious and expensive. Therefore, composite samples of the suppliers‘
milk are taken over a period and then tested. After thorough mixing,
proportionate amounts of the suppliers‘ daily delivery are collected and
placed into the patron‘s composite sample bottle.
● The total volume of the individual composite sample shall be not less than
175 ml.
● The bottle containing the composite milk sample shall be tightly stoppered
to prevent evaporation and kept in a freeze, away from light, till required for
analysis.
● The sample shall be analyzed on the same day as the last portion of milk
is transferred to the composite sample bottle.

14. ● Warm the milk samples in the bottle to about 40°C in a water bath and
mix thoroughly.
● Cool it to 26° - 28°C.
● Leave aside the samples for about 4-5 minutes after mixing to allow air
bubbles to rise and escape.
● After that, mix the sample by inverting the bottle 3-4 times and start
analysis.

15. Sampling from Individual, Several, Bulk Containers
● The sampling procedure followed for milk like in individual,
several or bulk containers can be applied to cream.
● When samples of cream is thin and in small containers, it shall be
mixed by plunging not less than 10 times.
● It is essential that whole cream should be thoroughly agitated and to
mixed. For thick cream, plunger can be used for proper mixing.
● To avoid whipping and churning, the disc of the plunger shall not be
brought above the surface of the cream.

16. ● When cream is thin and in small containers, it shall be mixed by plunging
atleast ten times.
● The position of the plunger shall be moved from place to place to ensure
that the whole of the cream at the bottom of the vessel has been thoroughly
agitated and mixed with the upper layer.
● To avoid whipping and churning, the disc of the plunger shall not be
brought above the surface of the cream.
● When cream is thick or in bulk containers, it shall be mixed by plunging
as same for thin cream.
● When the cream is sour, the material shall be warmed so as to attain a
temperature between 30° and 40°C and, while cooling it to room
temperature, the container shaken gently or the contents stirred. Keep the
contents covered as much as possible.
● In all cases the sample of cream shall be taken immediately after mixing.

17. One of the following methods are employed during sampling-
1. Sampling by cutting a sector-Using a knife with a sharp blade, two
random cuts are made radially proceeding from the centre of the
cheese/paneer towards the edge.
2. Sampling by means of a trier- The cheese trier is driven obliquely into the
surface of the paneer or cheese towards the centre once or several times at a
point at least 10 to 20 cm from the edge of the cheese.
3. However, when the cheese is delivered in drums, or other larger
containers, sampling may be carried out by driving the trier obliquely
through the content of the container from the top to bottom. This method is
suited for sampling of processed cheese.

18. ● Samples shall be prepared for chemical analysis by passing them
quickly through a suitable grater, by grinding them quickly in a
mortar and returning them to the sample container or by cutting them
into small pieces with a sharp knife in the container.
● Sampling by cutting
Use knife with a pointed blade
● Circular base
Make two cuts radiating from the centre of the cheese, when cheese is
circular in shape, after removing the inedible portion sample should be
minimum 150 gm.
● Rectangular base
Make cuts parallel to the sides. After removing the inedible portion sample
should be minimum 150 gm.

19. ● The sampling of khoa follows the procedure used for sampling
cheese/paneer/chhana, except that a clean dry stainless steel knife with sharp
pointed blade is used to cut khoa for sampling.

20. Bulk Units
The number of containers to be selected for sampling shall depend upon the lot size.
A random sampling procedure can be adopted for uniform quality of ghee as given
below:
Number of containers in the lot Number of containers to be selected
1 1
2-40 2
41-110 3
111-300 5
301-600 7
601 and above 10
If there is a possibility of wide variation among the different lots, e.g. in the
consignment from an individual producer, every unit shall be sampled. A composite
sample is prepared by taking equal amount of ghee from each of the container
selected.

21. ● For determination of moisture and organoleptic test sample is mixed
without heating in the container itself until homogeneous stage.
● For sensory evaluation, a little quantity of ghee is taken on back
palm of one hand and is lightly rubbed with the help of the other
hand.
● During this process, the aromatic constituents released due to
friction and body heat are inhaled. In addition or alternatively, a few
drops of melted ghee are put on the tongue for taste.
● After the determination of moisture, sample is heated in a water
bath to a temp. not higher than 50C till completely melted.
● It is filtered and clear and it is used for general analysis.

22. Bulk Units
If the butter is supplied in bulk units like boxes, a random sampling procedure shall
be followed as given below.
Number of units in the lot No. of units to be selected
1 1
2-9 2
10-49 3
50-99 4
100-199 5
Over 200 5 for the first 200 + 1 for each additional
200 units or by a fraction thereof.

23. ● The sample is warmed to a temperature not exceeding
39C or at the lowest possible temperature in an oven or
water-bath until by vigorous shakings a homogenous fluid
emulsion is obtained.
● For butter fat analysis, a portion of emulsified butter is
heated to 50 to 60C until the fat separates.
● The fat layer is filtered through a dried filter paper above
solidification point of fat by using hot water funnel.
● Clear filtrate free from water is used after mixing for
analysis of butter.

24. Bulk Units
If the product is supplied in bulk units, the number of units to be selected for
sampling shall normally be as follows:
Total no. of units No. of units to be selected
1 1
2 to 5 2
6 to 20 3
21 to 60 4
61 to 100 5
over 100 5 + one for each additional 100 units.
When there is a possibility of wide variations between different units, every units
shall be sampled.

25. ● The samples shall be stored at a temperature (not higher than -15°C).
During transit the samples shall be maintained at a temperature not
exceeding -15°C.
● Sample size of ice-cream shall not be less than 100 g.
● If necessary several packages of smaller size shall be taken to make up the
required size of sample.
● In multilayered ice-cream, the sample shall be such as to contain the same
proportion of each layer as is present in the original ice-cream.
● Different layers shall not be separated at the time of sampling and a
complete sample of all layers shall be placed in the sample jar.
● For the purpose of melting, the frozen sample may be kept at room
temperature or, if required, in water bath at a temperature not exceeding
45ºC for not more than 15 minutes. Thoroughly mix the Ice-Cream samples
before removal of the test portion.

26. Bulk Units
If the consignment is declared to consist of different batches of manufacture, the
batches shall be marked separately and the groups of containers in each batch shall
constitute separate lots. The containers from the lot shall be chosen at random and to
ensure the randomness of selection, a random number table as agreed to between the
purchaser and the vendors shall be used.
Lot size No. of containers to be selected
50 - 300 6
301 - 500 12
501 - 1000 15
1000 - and above 21
The sample containers selected shall be divided at random into three equal sets and
labeled with all the particulars of sampling.

27. ● On storage of condensed milk, separation of the constituents such as fat,
lactose may occur.
● It is necessary to mix the contents of the container prior to analyses in the
following manner:
● Heat the container in a water bath at about 40°C until the sample has
nearly reached this temperature. Open the container at the edge of the lid.
● Re-incorporate all the material adhering to the lid into the container.
● Mix the contents thoroughly by stirring with a spoon or spatula, in such a
way that the top layers as well as contents of the lower corners are moved
and mixed.
● Repeat the stirring before drawing the sample for testing various
parameters.