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CHEMISTRY
INVESTIGATORY
PROJECT
Name :
Class :
Roll No:
Year : 2014-2015
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Certificate
This is to certify that Keshav Jain of
Class XII-G, in the academic year 2014-
2015, has completed the project
To determine the amount of casein
present in different samples of milk.
under my guidance and supervisionand to my complete satisfaction.
______
Signature
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Acknowledgement
I express my sincere gratitude to Mrs.
Madhu Mahajan and Mrs. Anita
Sharma (Chemistry teachers) for theirvaluable guidance, and for giving useful
suggestions and relevant ideas that
facilitated an easy and early
completion of this project.
I also express my deep gratitude to our
lab assistants, who were instrumental
in this regard by providing all thenecessary materials required in this
project.
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IndexContents
Certificate
Acknowledgement
Aim
Description
Requirements
Procedure
Observation
Inference
Bibliography
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Aim
To determine the amount of
casein present in differentmilk samples.
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Description
Casein is the main protein constituent of milk.
It constitutes about 80% of the total protein
in cows milk and about 3% of its weight.
Proteins precipitate when milk is moderately
acidified. Casein is sparingly soluble in water,
but dissolves completely in alkalis or strong
acids. It is a complete protein, meaning that itcontains all the essential amino acids, which
the body cannot manufacture on its own.
When dried, it is a white, amorphous powder
without any taste and odour. It is a mixedphosphoprotein and occurs in milk as a
calcium salt (calcium caseinate) in the form of
micelles. The micelles have a negative charge.
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When an acid is added to the milk, the
negative charge is neutralized.
Calcium caseinate + acetic acid casein (s)
+ calcium acetate (aq)
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Requirements
Apparatus and Chemicals
250 ml beakersFunnel
Glass rod
Chemical balances
Test tubes
Filtration flask
Bunsen burner
Different samples of milk
1% acetic acid solution
Saturated ammonium sulphate solution
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Procedure
Take 20cc of cows milk in a clean, dry
beaker and add 20 mL of saturated
ammonium sulphate solution with
constant stirring. Fat and casein will
precipitate out.
Filter the solution and transfer the
precipitate into another beaker.
Add 30 mL of water to the precipitate.
Only casein dissolves in water, forming a
milky solution and leaving all the fat
undissolved.
Heat the milky solution to about 40C andadd 1% acetic acid solution drop wise,
when casein gets precipitated.
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Filter the precipitate, wash with water
and let the precipitate dry.
Weigh the dry solid mass in a previously
weighed watch glass.
Repeat the experiment with other
samples of milk.
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Observation table
Volume of milk taken in each case = 20 ml.
Name of the milk Weight of casein % of casein
Cow milk 0.68 g 3.4
Buffalo milk 0.84 g 4.2
Goat milk 0.66 g 3.3
Sheep milk 1.10 g 5.5
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Inference
Different milk samples
contain differentpercentages of casein.
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Bibliography
NCERT Class 12 Chemistry
Comprehensive PracticalChemistry
www.sciencebuddies.org
www.wikipedia.org
http://www.wikipedia.org/http://www.wikipedia.org/http://www.wikipedia.org/