The document provides a comprehensive overview of milk processing, detailing the steps from receiving and testing raw milk to packaging and distribution. Key processes include pasteurization, homogenization, and quality control measures, emphasizing the importance of maintaining milk's quality and safety during handling. It discusses various methods for milk cooling, filtration, and storage designed to prevent contamination and ensure the product is safe for consumption.

1. Unit 7: Processing of raw milk.
7.1 Receiving, weighing and sampling of milk
7.2 Platform and routine tests of milk
7.3 Straining and filtration of milk in brief
7.4 Milk cooling methods and their importance
7.5 Milk Pasteurization, Milk homogenization & emulsification and their importance
7.6 Heating system of milk
7.7 Concept of toning and standardization of milk in brief
7.8 Milk packaging, distribution and storage of milk at dairy processing unit
Milk Processing
Milk processing is activities related to handling or modification of milk into different
products from the farm to processing plant. Milk should be collected as quickly as possible
before any contamination and physical-chemical changes, then, it should be transported to
the milk plant hygienically as soon as possible and it must be processed, pasteurized,
homogenized, packaged & distributed to the consumer’s hand before they get up in the
morning. The main objective of milk processing is maintained the milk and milk product’s
quality by different treatments or methods of milk
Processing. Processing of liquid milk includes the following methods:
1. Receiving
(a) Unloading (b) Grading (c) Sampling (d) Weighing (e) Plat form tests
2. Collection, cooling and transportation
3. Straining, filtration, clarification, and bactofugation
4. Toning and standardization
5. Emulsification
6. Homogenization
7. Pasteurization
8. Sterilization
9. Packaging and distribution
10. Storage of milk and products
1. Receiving milk
When milk is received at the milk plant, it should be at 50C or below. Milk should be clean,
sweet, of pleasant flavor, free from off-flavors and reasonably free from extraneous material.
Contamination with antibiotics pesticides and other chemicals or metals is highly
undesirable. No abnormal milk should be accepted. Milk receiving process included
following:

2. (a)Unloading: The motor, truck carrying the filled milk cans is backed up to the unloading
platform. The milk cans are then unloaded manually. If a milk tanker is being used, it is first
properly positioned and unloads the milk.
(b) Grading: It refers to classification of milk on the basis of quality, for price fixing
purposes. It is well known that the quality of the finished products depend on that of the raw
material used. The principle of grading is based on organoleptic test, such as those for smell
test, appearance, touch, acidity, sediment etc. These are included under plat form tests. The
plat form tests includes all those tests which are performed to check the quality of the
incoming milk on the receiving plat form, so as to make a quick decision regarding its
acceptance/ rejection. The various plat form test are as follows:
 Smell of the milk
 Appearance of the milk
 Temperature of the milk
 Sediment test
 Acidity test and pH
 MBR test
 COB test
 Lactometer reading
 Fat% estimation
(c) Sampling: - A sample is a part of any thing represented as evidence of the quality of the
whole amount. The method of sampling depends upon the material involved and the purpose
of the sample. The sample of milk to be used as part of the composite is taken either with a
sampling tube or with a small dipper.
(d). Weighing: - In dairy farm, milk volume is directly measured by using measuring rod or
measuring stick that is very common at collection center also. The milk-in-cans dumped into
the weigh tank, either manually or mechanically.
Quality control tests: The sample should be tested in the quality control laboratory for final
acceptance/rejection. Plate form tests are performed regularly for giving quick decision of
acceptance or rejection of milk. It includes acidity, fat, SNF, COB, sediment tests.
The common quality control tests are as follows:
 Acidity test: Applied as a platform test to determine final acceptance/rejection of
milk.
 Ethanol (alcohol) test: Applied as a platform test to determine the heat-stability and
pH of milk.
 COB (clot on boiling) test: Applied as a platform test to determine the heat-stability
of milk.
 MBR (Methylene Blue Reduction) test: Applied as a platform test to determine the
extent of bacterial contamination and growth in milk.
 DMC (Direct microscopic count): Applied as a laboratory test to identify the types
of microorganisms present in milk.
 SPC (Standard plate count): Applied as a laboratory test to determine the extent of
bacterial contamination and growth in milk.
 Lactometer reading: Applied as a platform test to detect adulteration of milk with
water.

3.  Freezing point of milk: - Applied as a laboratory test to detect adulteration of milk
with water.
 Fat and /or SNF test: Applied as a laboratory test to make payment for milk received.
2. Collection, Cooling and Transportation of milk
Collection of milk
In almost all developed and developing countries milk production is confined to rural areas
whereas demand is in urban oriented nature. Hence the milk has to be collected from
production points of milk shed areas to processing & distribution of milk in cities areas. The
common systems for collection of milk in given as Milk is collected by 3 methods i.e.
Cooperatives, contractor and individual basis.
Cooling of milk:
Milk produced even under very best conditions contains some microorganisms, their
numbers increases during subsequent handling. Milk microorganisms grow best between 20
-40°C. Milk must be cooled to 5°c or below and also held at that temperature till processed
as soon as possible in order to check the growth of the organisms present and maintain the
keeping quality of milk.
Methods of cooling: -
1. Can-immersion method: In this method tank is made with concrete floor or stainless
steel material, which is filled with chilled water at low temperature or tap water and ice block
mixture. Milk with can is emerged into tank for chilling purpose. After short duration milk
is taken out for transportation to collection center or further processing.
2. Tubular cooler: In this method, milk is passing through coil-pipe lines for chilling
purpose and collected in a container placed at lower level of tank. It is just like an autoclave
having a chamber with coiled or pipelines. The coils or pipelines are distributed inside the
tank having chilled water at lower temperature. The milk passes through the pipelines & get
chilled which is collected in lower surface container.
3. Surface cooler methods: In this method milk is distributed over the outer surface of the
cooling tubes from the top by means of a distributor pipe or trough and flows down in a
continuous thin stream. Plates are tubular or spherical in shaped placed vertically. The
cooling medium, mostly chilled water is circulated in the opposite direction through the
space between the plates. The chilled or cooled milk is received below in a receiving trough
from where it is discharged by a pump.
4. Bulk tank cooler method: Properly designed bulk milk tank coolers, which is run by a
mechanical refrigeration system. Tank is made up of stainless steel with proper sized and
shape depending upon the quality of milk, which cool the milk rapidly to a low temperature
(5°C or below) and automatically maintain this temperature during the storage period of milk
and milk products
Transportation of milk: - In Nepal, milk has to be regularly collected and transported twice
a day (morning & evening). A mode of transportation depends upon the carrying load, the
distance of collection and local conditions. Means of transportation in our country are head
load, bicycle, rickshaw, bullock-cart, pack animal, three wheeler & milk van. In dairy
developed countries the milk is transported by buses, road tanker, railway tank, aircrafts etc.

4. 3. Straining, Filtration, Clarification and Bactofugation
Foreign materials such as dust, dirt, feeds, bedding, manure, dandruff, hairs, flies and many
other substances may be find in milk because of careless handling of milk at the dairy farm.
This occurs mainly at the time of milking. Straining, filtration, clarification and
bactofugation are essential to save the milk from these materials.
Straining
It is the procedure of removing some of the larger particles of foreign materials. The strainer
may be constructed like a funnel with straining cloth or pad. The larger particles such as
straw, hairs, insects, gross dirt etc. are removed. Microorganisms are so smaller that it easily
passes through strainer without any resistant.
Filtration
Filters possess pores much smaller than the ordinary strainer, cloth or metal. Milk-filtration
devices,which are provided with closely woven cotton cloths, have been used. These filters
are very fine and provide a much more efficient filtering capacity. They are found to be
effective in removing visible sediment from milk but do not filter out the leucocytes,
epithelial cells, cell fragments or microorganisms unless these are trapped on the large
particles which make up the visible sediment.
There are two types of filtration.
1. Cold milk filtration: In this method filtration is done at lower temperature. But at low
temperature milk is more viscous so rate of filtration is slow.
2. Hot milk filtration: In this method filtration is done at higher temperature of milk. At
high temperature milk is less viscous so filtration rate is fast.
Clarification
Clarification consists of using centrifugal means of removing sediment, solids, cells etc.
from fluid milk. In general appearance and construction, clarifiers are quite similar to
centrifugal cream separators. Clarifier is the most effective, practical device which is
available for improving the quality of milk by removing foreign material most of the dirt,
filth, and cell debris present in milk is of higher specific gravity than the milk. The efficiency
in removing insoluble dirt is very high.
Bactofugation
The centrifuge that also removes bacteria with centrifugal force is called bactofugation.
Machine is called bactofuge and having speed more than (4-5 times) than the normal clarifier
i.e. 20,000 rpm. At this speed the bacterial colonies are also get separated along with
sediments. So, if milk is subjected through bactofuge, about 99% of bacterial count is
reduced. It is a process of removing 99 percent of the bacteria in milk by centrifugal force.
It is mostly used for lab and research purpose for quality assurance.
4. Toning and standardization of milk
Toning: Toned milk refers to the milk obtained by the addition of water and skim milk to
the whole milk. In practice whole buffalo milk is mixed with reconstituted spray dried skim
milk for its production. Toned milk should contain a min of3% fat and 8.5% SNF.
Standardization of milk refers to the adjustment (raising or lowering) of milk constitutes to

5. desired value, so as to conform to the legal or other requirements prescribed. The
standardization can be done by partial skimming of fat in the milk with a cream separator,
or by admixture with fresh or reconstituted skim milk in proper ratio. The standardized milk
for liquid consumption should contain a minimum of 3.5 percent fat and 8.5 percent solid-
not-fat throughout the country.
5. Emulsification
Emulsification acts on the fat globule, after emulsification of milk, Fat globules are equally
distributed in container but do not reduce its size. In general there are two types of machines
used for the emulsification of milk and cream called emulsifier, has the outer appearance of
a cream separator.
6. Homogenization
The process of making an emulsion of milk fat and milk liquid by mechanical treatment is
termed “homogenization”. It makes the mixture of homogenous milk by reducing size of fat
globules. The homogenizations consist in the subdivision of the fat globules into smaller
globules. This process increases the viscosity so that milk with a somewhat lower fat content
appears as viscous and slightly richer milk. The machines used for this purpose are known
as homogenizer.
7. Pasteurization
Pasteurization refers to the heating every particles of milk or milk products to at least 145°
F (63°C) for 30 minutes, or to at least 161°F (72°C) for 15 seconds or any other temperature-
time combination which is equally efficient. Pasteurization is the heating of raw milk to
destroy the pathogenic or disease producing organism which may be present in milk.
The purposes of pasteurization are as follows:
1. To render milk safe for human consumption by destruction of cent percent pathogenic
micro-organisms.
2. To improve the keeping quality of milk by destruction of almost all spoilage type of
microorganisms (85-99%).
3. To improve keeping quality of milk and milk products.
Advantages
1. This process destroys common disease producing bacteria such as of tuberculosis, typhoid,
brucellosis etc.
2. Keeping quality of milk should be improved.
3. Inactivates the undesirable enzymes that produce off flavor like phosphatase enzyme.
Disadvantages
1. It reduces the cream line or cream volume.
2. Pasteurized milk does not clot with rennet enzymes.
3. It fails to destroy bacterial toxins in milk.
4. It may be used to make low-quality milk.

6. 5. Careless pasteurization gives false sense of security.
Methods of pasteurization: - The time temperature relationship has led to the use two
different methods of pasteurization.
1. L.T.L.T. method (long time low temperature): - In this methods of pasteurization, milk
is heated to 63°C for 30 minutes.
2. H.T.S.T (High temperature short- time) methods: - In this methods milk is heated to 71°C
for 15 seconds and immediately cooled to 5°C or below. The entire process is continuous
and automatic and is electrically controlled.
8. Sterilization
This denotes a process of heating of milk to such an extent that all the microorganisms
including their spores are completely destroyed. Sterilized milk may be defined as milk
which has been heated to a temperature of 100°C or above for such lengths of time that it
remains fit for human consumption for at least 7 days at room temperatures. Usually the milk
is sterilized at 108-111°C (225-2300F) for 25-30 minutes.
9. Packaging and distribution of milk
Packaging
Packaging means placing products into a protective wrapper, box or container for transport
or storage. Packaging is the technique of using the most appropriate containers and
components to protects, carry, identify of any products. It constitutes a vital link between the
manufacturer and eventual consumer for the safe delivery of the product through the various
stages of manufacture, storage, transport, distribution and marketing,
Packaging materials: These includes paper and paper-based products (coated or lined),
glass, tin-plate, aluminum foil, timber (wood), plastics and laminates.
Types of packaging:
Bulk packaging: It is done in Can or any contamination free tank. It is done for distribution
of milk in hostel, hotel, and hospital and dispensary unit.
Small packaging: Packaging is done in small bottle and poly pack pouches. It is done for
distribution of milk for home consumption. It is of two types i.e. Multi and single service
container.
Multiservice container: Different types and different sized of bottles are used for multi
service packaging. In this case same bottles are using several times for packaging i.e.250,
500, 1000 ml bottle.
Distribution
Distribution of milk is the last or final stage of the market milk industry. Others are
preparatory to placing the product into the hands of the consumer. The quality of the product
alone will not assure its wide distribution, which should be planned intelligently.
Methods of distribution:
Door to door delivery: It is applicable for small scale production unit because sales man
has to visit door to door of consumers. It is time and labour consuming method. Milk

7. producers’ or distributors’ carry small quantity of milk for distribution in small localities
with regular delivery of milk and periodically payment of distributed quantity of milk.
Booth system: It is more suitable for populated areas like market and cities. Most of the
dairy developed countries are using this system of distribution of milk like Denmark, Canada
etc. In this system booth is fixed to different localities from where milk is distributed
regularly.
Bulk supply unit: It is applicable for large scale production unit. In this system large
quantity of chilled, contamination free and sealed container milk is distributed to the hostel,
hotel, hospital and army unit.
Bulk dispensing unit:
In this system a separate big refrigerated room is prepared where chilling facilities are
provided properly. Large quantity of milk (1000-10000 liter) is kept under refrigeration
system from where it is distributed to the consumers through pipelines or consumers have to
purchase the required quantity of milk from the supply unit.
10. Storage of milk and milk products
Storage
In storage process, storage tanks are used in milk plants for the storage of raw, pasteurized,
or processed products, often in very large volumes. Because of the longer periods of holding,
storage tanks are among the most important items of equipment.
Purpose of storage
1. To maintain milk at a low temperature so as to prevent any reduction in quality
2. To facilitate enough raw milk supply
3. To allow for continuous operation during processing and bottling.
4. To facilitates standardization of the milk.