I would like to express my sincere gratitude to my
Chemistry mentor Miss Deepika Arora for their
vital support, guidance and encouragement without
which this project would not have come forth
from my side.
Special thanks of mine goes
to my colleagues who helped me a lot in completing
the project by giving interesting ideas, thoughts &
made this project easy and accurate. I wish to
thanks my parents for their undivided support &
interest who inspired me & encouraged me to go
my own way, without which I would be unable to
complete my project. And at last by no means
the least I would thank to God who made all the
VALUE OF MILK AS FOOD
Milk is a complete diet as it contains proteins,
carbohydrates, minerals, fats, vitamins and water in it.
Casein is the major protein constituent of present in the
milk and is a mixed phosphor-protein.
Casein has isoelectric pH of about 4.7 and can be easily
separated around this pH. It readily dissolves in dilute
acids and alkalis.
Casein is present in milk as calcium-caseinate in the form
of micelles. These micelles have negative charge. On
adding acids to milk the negative charges are neutralized.
AIM To study the quantity of Casein in different
samples of milk.
Milk is the whit fluid produced by the female of warm-blooded
animals for feeding her young ones. Animals that produce milk
directly gives birth to their offspring are called mammals.
In mammals the blood is pumped from the heart to the mammary
glands. The mammary glands are able to separate different
substances from the blood and combine them to make milk.
Milk has been called as natures most perfect and complete food. It
provides all the nutrients, which are required by the human babies
and other young mammals need for the growth and development.
Value of Milk as Food Cows milk contains about 87% of water and 13% of solids. These
solids contain nutrients of milk.
Nutrients of milk
Our body needs five kinds of nutrients daily for our good health,
growth, development, and replacement of worn out tissues. These
nutrients are required by our body to get energy to perform various
metabolic activities in daily life. These nutrients are:
These are the major source 0f energy for our body. Carbohydrates
are also called Polyhydroxyl aldehyde or Polyhydroxyl ketone.
Carbohydrates content of milk is mainly lactose of milk sugar. In
addition to provide energy, lactose helps the body to absorb
minerals, calcium, and phosphorus in milk. Our bones and teeth are
largely consisting of these minerals. Lactose also gives sweetness
Like carbohydrates fats also provides energy. They also supply
certain fatty acids that our body must have. Fat give milk its rich
flavor. Milk fat contains vitamins and several other substances.
One of these substances is carotene which our body converts into
vitamin-A. Milk fat appears as tiny globules.
They help the body to grow and remain healthy. Calcium and
phosphorus is the most important mineral of milk. In fact, milk is
the chief food source of calcium. Other minerals in milk include
potassium, odium, sulphur and small amount of aluminium,
copper, iron, iodine, manganese and zinc.
Like minerals help the body and maintain it, they also supply
energy. The protein contains all required amino acids for building
blood and tissue. Only egg protein and the proteins in some meat
have higher food value than milk proteins content of milk.
These are essential for growth maintaining tissue and prevention
of such diseases night blindness, beriberi, scurvy and rickets due to
deficiency of vitamin-A, vitamin-B, vitamin-C, and vitamin- D. Milk
provides more vitamins and in larger amount then most of the
other natural foods. Milk is an excellent source of vitamin-A and B2
and a good source of vitamin-B1. Other vitamins include C, K, E, B6,
B12 and Niacin. Milk also has vitamin-D the quantity is very low. In
some countries, diaries add extra vitamin to milk.
All mammals contain the same nutrients but these nutrients are
not at all identical in kind or in quantity. Compared with cows
milk, for example, the milk from a water buffalo has 3 times as
much as protein but three quarters the amount of sugar. Human
milk has fewer proteins and minerals than cows milk but contains
1.5 times more sugar.
In almost every country with dairy industry, whole milk is sold, as
food must meet certain standards most countries insist that whole
milk should contain at least 3.0% milk fat and up to 8.5% non fat
milk solid. Some require a higher percentage of about 3.5% milk
fat, 5.0% lactose, 3.5% proteins and 0.7% minerals. The percentage
differs between individual cow breeds. The quantity and
composition of milk also depends on what a cow feed and how the
animal is cared.
Milk is a complete diet as it contains in its Minerals,
Vitamins Proteins, Carbohydrates, Fats And Water. Average
composition of milk from different sources is given below:
Source of Milk
COW 87.1 0.7 3.9 3.9 4.9
HUMAN 87.4 0.2 4.0 4.0 4.9
GOAT 87.0 0.7 4.2 4.2 4.8
SHEEP 82.6 0.9 5.5 6.5 4.5
Caesin is a major protein constituent in milk & is a mixed
phosphor-protein. Casein has isoelectric pH of about 4.7 and
can be easily separated around this isoelectric pH. It readily
dissolves in dilute acids and alkalies. Casein is present in milk
as calcium caseinate in the form of micelles.
> Beakers (250 ml)
> Glass rod
> Weight box
> Filtration flask
> Buchner funnel
> Test tubes
> Porcelain dish
> Different samples of milk
> 1 % acetic acid solution
> Ammonium sulphate solution
THEORY Natural milk is an opaque white fluid Secreted by the
mammary glands of Female mammal . The main
constituents of natural milk are Protein, Carbohydrate,
Mineral Vitamins, Fats and Water and is a complete
balanced diet. Fresh milk is sweetish in taste. However ,
when it is kept for long time at a temperature of 5 degree it
become sour because of bacteria present in air. These bacteria
convert lactose of milk into lactic acid which is sour in
taste. In acidic condition casein of milk starts separating
out as a precipitate. When the acidity in milk is sufficient
and temperature is around 36 degree, it forms semi-solid
mass, called curd. Casein is present in milk as calcium
caseinate in the form of micelles. These micelles have
negative charge and on adding acid to milk, the negative
charges are neutralized.
Casein (/kes.n/ or /kesin/, from Latin caseus,
"cheese") is the name for a family of related phosphoproteins
(S1, S2, , ). These proteins are commonly found in
mammalian milk, making up 80% of the proteins in cow
milk and between 20% and 45% of the proteins in human
milk. Casein has a wide variety of uses, from being a major
component of cheese, to use as a food additive, to a binder for
safety matches. As a food source, casein supplies amino
acids, carbohydrates, and the two inorganic elements
calcium and phosphorus.
Casein contains a fairly high number of proline residues,
which do not interact. There are also no disulfide bridges. As
a result, it has relatively little tertiary structure. It is
relatively hydrophobic, making it poorly soluble in water. It
is found in milk as a suspension of particles called "casein
micelles" which show only limited resemblance with
surfactant-type micellae in a sense that the hydrophilic
parts reside at the surface and they are spherical. However,
in sharp contrast to surfactant micelles, the interior of a
casein micelle is highly hydrated. The caseins in the
micelles are held together by calcium ions and hydrophobic
interactions. Any of several molecular models could account
for the special conformation of casein in the micelles. One of
them proposes the micellar nucleus is formed by several
submicelles, the periphery consisting of microvellosities of
-casein. Anoher model suggests the nucleus is formed by
casein-interlinked fibrils. Finally, the most recent model.
proposes a double link among the caseins for gelling to take
place. All three models consider micelles as colloidal
particles formed by casein aggregates wrapped up in soluble
The isoelectric point of casein is 4.6. Since milk's pH is 6.6,
casein has a negative charge in milk. The purified protein is