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Components in Milk and Isolation of Milk Protein (Casein)

Paper Type: Free Essay Subject: Chemistry
Wordcount: 1963 words Published: 30th Nov 2017

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1.1 Introduction

1.2 Objective

1.3 Materials used

1.4 Methodology

1.5 Result

1.6 Discussion

1.7 Conclution



Milk is a complex biological fluid with high amount of proteins, lipid and minerals. Milk plays a major role in a healthy, balanced diet throughout lifetime. Milk having Proteins, Vitamins, carbohydrates and other minerals.Caseins, lactalbumins, and lactoglobulins are some proteins in milk. Milk from domesticated ruminants, primarily cow, sheep, goat, camel and buffalo, are major sources of dietary calcium and, in countries where commercially available milk is fortified, of dietary vitamin D (Clemens et al., 2014).

Casein is a sort of protein found in dairy items, for example, milk, yogurt, chocolate, ice-cream and foods. Casein protein, whether it originates from sustenance or from a supplement, could be a valuable addition to diet with a few benefits. Casin helps to digest food fast ,it can take 7h to digest (Samuels, 2014)

Milk holds 3.3% total protein. Milk proteins hold each of the 9 essencial amino acids needed by humans. Milk proteins are blended in the mammary organ, however 60% of the amino acids used to manufacture the proteins are from the cow’s eating diet. (Milkfacts.info, 2014)

The total protein part of milk is made out of various particular proteins. The essential gathering of milk protein is casein. the distinctive caseins are different atoms but are comparable in structure. All different proteins are found in milk. (Walter and Hurley, 2014)

Caseins got proper amino acid composition that is critical for development and improvement of the nursing youngs. (Walter and Hurley, 2014)

A protein is an unbranched polymer in which the monomer units are amino acids. All the more particularly a protein is a peptide less than 50 amino acids are available. Proteins arranged into two: fibrous and globular.fibrous proteins are proteins which peptide chains are organized in long strands or sheets. Globular proteins will be proteins that have a tendency to overlap again on themselves into compact spheroidal shaped. Globular proteins don’t form inter molecular between protein units and are all the more effectively solubalized in water . Because that they hold all the amino acids key for building blood and tissue, and can manage life and normal growth . Milk holds three proteins that are caseins, lactalbumins, and lactoglobulins (spurlock,2014)

1.2 Objective

To Understand and isolation the components which are present in milk and isolation of milk protein (Casein).

1.3 Materials used

Albumin solution

Solid ammonium sulphate


Sulphur salicylic acid

Trichloroacetic acid

Lead acetate solution

1% Acetic acid

Milk powder

Filter cloth


Test tubes



Bunsen burner

Test tube holder

Electric balance

Watch glass

1.4 Methodology

Protein precipitation

Precipitation by salt

Half saturation with ammonium sulphate

To 3ml of albumin added equal volume of ammonium sulphate solution. Mixed and allowed to standed for 5min. filtered and performed the Biuret test with the filtrate

Full saturation with ammonium sulphate

To 3ml of albumin added solid ammonium sulphate with mixed until the solution is saturated and stand for 5min. filtered and performed the Biuret test with the filtrate.

Isoelectric precipitation

To 3ml of casein added 3 drops of bromocresol green indicator. Added 1% acetic acid drop by until a green color is obtained which indicates that the pH is closed to4.6

Precipitation by organic solvents

To 2ml of albumin was added with 4ml of ethanol. Mixed and let it stand. And observed the reaction

Precipitation by acidic agents

Albumin 1ml was added an equal volume of picric acid solution. Observed the3 formation of thick precipitate. repeated the test with trichloroacetic acid and sulphosalicylic acid.

Precipitation by heavy metal ions

To 1ml of albumin, added to 10 drops of lead acetate solution. Observed the formation of precipitate. Repeated the test with lead nitrate solution

Precipitation of heat and Acid

Took 10ml of albumin to the test tube, hold the test tube over a flame in slant position and boiled the upper part of the solution .A cloudy white precipitate will be observed in the heated portion. Added a few drops of 1% acetic acid . coagulation was take place and albumin is precipitated.

Isolation of casein from milk

Milk powder of 17.5g was taken into a beaker. 62.5ml of warmed water at 450C was boiled by using Bunsen burner and added into the beaker which is containing milk powder. The milk powder was well stirred. 10% of acetic acid was added drop wise into milk powder solution and stirred well until the solution changes from milky to pale yellow. Then the solution was filleted well and taken into a beaker, and 15ml of ethanol was added to the filtered casein, it was kept for 10 minutes. After 10 minutes the casein with ethanol was filtered and dried well by using filter paper and tissue papers. The well dried casein was weighted and weight was recorded

1.5 Results




Ppt by Heat/acid

When heating there was a ppt form after adding acetic acid the ppt diffused.

There fore these methods can be used for the ppt protein

Ppt by heavy metal ions

White ppt was formed when lead nintrate was added

By the addition of heavy metals protein can be ppt

Ppt by acidic agents

A thick ppt was formed

Positive,there fore via this method protein can be ppt

Ppt by organic solvents

White ppt was formed

Positive, then using organic solvent protein can be ppt

Full saturation with NH4SO4

White ppt formed


1.6 Discussion

The casein isolation, Kept temperature 45 degrees for avoid excess heat and dilute acetic acid was added as drop by drop. It is important that the heating not be excessive because this conditions hydrolyze the lactose into its components, glucose and galactose before its isolation

Adding of Calcium carbonate to the original beaker containing the liquid, neutralized the excess acetic acid and precipitated the initially soluble protein, albumin. This step ensures the liquid contains only the lactose and albumin was poured away from the lactose(Chemistry.mcmaster.ca, 2014)

Casein is not properly dry

All of the calculations were done

1.7 Conclution

Obtained casein after isolation; 12.25g

%yield = (12.25/17)x100

= 72%

Caseins have an appropriate amino composition, it’s important for the growth of young.This protein in dairy animals.so many pepole allergic to milk, but trully they allergic to the components that milk contains: the casein and the lactose. Evacuation of these items especially the casein permits people with hypersensitivities to endure milk. The information is totally useful for peoples who can`t eat immoderately milk (Leonce, 2014)


Chemistry.mcmaster, (2014) Chem2O06 – 1997/98 – Experiment 11.[Online]. 2014. Available at: http://www.chemistry.mcmaster.ca/~chem2o6/labmanual/expt11/2o6exp11.html. (Accessed: 15 July 2014).

Clemens, R., Hernell, O, and Michaelsen, K. (2014) Milk and Milk Products in Human Nutrition.[Online]. 2014. Nestlenutrition-institute.org. Available at: http://www.nestlenutrition-institute.org/Resources/Library/Free/workshop/BookNNIW67/Pages/booknniw67.aspx. (Accessed: 14 July 2014).

Leonce, D. (2014) Biochemistry Practicals.[Online]. 2014. Academia.edu. Available at: http://www.academia.edu/3491493/Biochemistry_Practicals. (Accessed: 15 July 2014).

Milkfacts.info, (2014) Milk Protein | MilkFacts.info.[Online]. 2014. Available at: http://www.milkfacts.info/Milk Composition/Protein.htm. (Accessed: 14 July 2014).

Samuels, M. (2014) Casein Protein Benefits | LIVESTRONG.COM.[Online]. 2014. LIVESTRONG.COM. Available at: http://www.livestrong.com/article/86604-casein-protein-benefits/. (Accessed: 14 July 2014).

Spurlock, d. (2014) Isolation and Identification of Casein From Milk Course Notes. [Online]. 2014. Homepages.ius.edu. Available at: http://homepages.ius.edu/dspurloc/c122/casein.htm. (Accessed: 14 July 2014).

Walter, L. and Hurley, (2014) Milk Composition – Proteins. [Online]. 2014. Ansci.illinois.edu. Available at: http://ansci.illinois.edu/static/ansc438/Milkcompsynth/milkcomp_protein.html. (Accessed: 14 July 2014).



Higher National Diploma in Biotechnology



Module Name

Protein precipitation and casein from milk

Module Number


Name of Candidate


Submission Date

15 July 2014

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