CHEMISTRY PROJECT

Qualitative &Qualitative & QuantitativeQuantitative

Analysis of MilkAnalysis of Milk

Mohit TomerSTD.XII-A

ACKNOWLEDGEMENT

I am really grateful to the chemistry department of our school, our teachers, Mrs. Bharti maam for the successful completion of this project

(Mohit Tomer)XII – A

CERTIFICATE OF ORIGINALITY

This is to certify that Mohit Tomer is a bonafide student of class XII – A, Cambridge School, Greater Noida and the following project is of his own compilation.

Signature

INTRODUCTION

A good project is the one that has creative ability, is based on scientific thoughts, is not biased, and is for the service of mankind.

These days we drink milk everyday but how many of us do really know what it is? Therefore, the project ‘ANALYSIS OF MILK’ enables us to analyze the various contents of milk.

Milk is a white opaque fluid secreted by mammary glands of females, and has a high food value due to the presence of the various constituents etc, (which are discussed in this project)

We hear everyday about the quality of milk. But what is the quality of the milk?

The quality of milk is characterized by its acidity. As we store the milk, its acidity gradually increases because of formation of lactic acid from milk sugar under the influence of ‘lactic acid bacteria’ from air. The acid precipitates the proteins of milk and, thus causes setting of milk. Generally, setting of milk is by heating it and then allowing it to stand undisturbed for some time but, it can also be observed without the above process, when its acidity is considerably high.

QUALITATIVE ANALYSIS

I. CARBOHYDRATES

General Information: Carbohydrates are one of the important components of food. These are the compounds of carbon, hydrogen and oxygen with general formula CxH2yOy.

Chemically, a carbohydrate is either a polyhydroxy aldehyde (e.g. Glucose), a polyhydroxy ketone (e.g. Fructose) or a substance, which on hydrolysis yields at least one of these polyhydroxy compounds. Carbohydrates have been divided into three classes namely:1. Monosaccharides, e.g. glucose, fructose, etc.2. Disaccharides, e.g. sucrose, lactose, etc.3. Polysaccharides, e.g. starch, cellulose, etc.

Some of the foods such as rice, potato, bread, cereals, fruits and milk etc. contain carbohydrates.

TEST FOR CARBOHYDRATES

Apparatus: Beakers, test tubes, burner and stirring rod

Chemicals: Milk, Benedict’s solution, Fehling’s solution A, Fehling’s

Solution B, dilute hydrochloric acid

Experiment Observation Inference1. Take 1 ml of milk in a

clean and dry test tube. Add 0.5 ml of HCl and warm. Add Fehling’s solution A

A red precipitate is observed.

Carbohydrates are present.

and warm. Then, add Fehling’s solution B and again warm.

2. Take 1 ml of milk in a clean and dry test tube and add 0.5 ml of Benedict’s solution and boil for 2 minutes.

Yellow or red precipitates are observed.

Carbohydrates are present.

Result: Carbohydrates are present in Milk.

II. PROTEINS

General Information: Proteins are nitrogenous substances, which occur in the protoplasm of all animal and plant cells. They are mainly required for building up tissues and in regeneration of cells. They are very complex compounds, containing carbon, hydrogen, nitrogen, oxygen, sulphur and

phosphorous. The chemical behaviour of proteins is due to the amino acids in the protein molecules.

Proteins, like polysaccharides, are all polymeric substances. All proteins, when subjected to treatment with strong acids, depolymerise into their monomeric components, all of which are L-amino acids of the following general formula:

The symbol R represents an organic radical, which may range from an H-atom to a large aliphatic or aromatic group.

Muscles, skin, hair, nails, blood, milk, eggs, beans, peas and pulses contain a high percentage of proteins.

TEST FOR PROTEINS

Apparatus: Beakers, test tubes, china dish, burner and stirring rod

Chemicals: Milk, hydrochloric acid, copper sulphate solution,

Ammonium hydroxide solution, acetic acid, concentrated nitric acid and 40% sodium hydroxide solution

Experiment Observation Inference1. Biuret test: Take 1 ml

of milk in a clean and dry test tube. Add 0.5 ml of CuSO4 solution and a few drops of NH4OH.

2. Take 1 ml of milk in a clean and dry test tube and add 0.5 ml of HCl or CH3COOH.

3.1 Take 3 ml of milk in a clean and dry test tube. Add 2 drops of conc. HNO3 along the sides of the tube and boil.

3.2 Cool the test tube and add excess of 40% NaOH or NH4OH to make the

Violet colour appears.

Protein separates as a precipitate.

A white ppt. is formed which changes to yellow

Yellow colour changes to orange

Protein is present.

Protein is present.

Protein is present.

Protein is present.

solution alkaline.

Result: Proteins are present in Milk.

III. FATS

General Information: Fats are triglyceride esters of fatty acids. They act as a primary reserve source for the living organisms and also protect them from physical shocks.

Glycerides of unsaturated fatty acids like oleic acid (C17H33COOH) are termed unsaturated fats. Similarly, glycerides of saturated fatty acids like stearic acid (C17H31COOH) are called saturated fats. These are excellent fuels. Fats protect delicate tissues and some of them are important sources of necessary vitamins.

Animals, fed on fat-free diet over an extended period, were found to suffer from skin eruption. The chief sources of fats are vanaspati ghee, milk, butter etc.

TEST FOR FATS

Apparatus: Beakers, test tubes, filter paper, burner and stirring rod

Chemicals: Milk

Experiment Observation InferenceCentrifuge the milk and get the fat. Take it on the filter paper and crush it.

Oily spot is observed.

Fat is present.

Result: Fats are present in Milk.

IV. PHOSPHATES

General Information: Phosphorous is a microelement, derived from the mineral salts, present chiefly in vegetables and milk. It is chiefly required to build the body tissues and phosphates and essential components of fluids, which regulate cellular activity.

TEST FOR PHOSPHATES

Apparatus: Beakers, test tubes, china dish, burner and stirring rod

Chemicals: Milk, concentrated nitric acid and ammonium molybdate

Solution

Experiment Observation InferenceTake 0.5 ml of milk in a china dish. To it, add 2 ml of conc. HNO3 and ammonium molybdate solution in excess and heat.

Canary yellow precipitate is observed.

Phosphate is present.

Result: Phosphates are present in Milk.

V. WATER

General Information: the specific gravity or relative density of milk lies in the range of 1.025 to 1.036. Pure milk does not contain any nitrates but when the mineral water is added to milk, nitrates are formed in milk and hence water contains some nitrates.

TEST FOR WATER

Apparatus: Beakers, test tubes

Chemicals: Milk, diphenylamine reagent solution

Experiment Observation InferenceTake 5 ml of diphenylamine solution in a test tube and pour the milk sample along the sides of the test tube.

A blue ring is formed.

Water is present in the sample.

Result: Water is present in Milk.

QUANTIATIVE ANALYSIS

I. DETERMINATION OF ACIDITY OF MILK

Apparatus: Beakers, conical flask, burette, pipette and burette stand

with clamp

Chemicals: Milk, distilled water, alcoholic solution of phenolphthalein

and 0.1 N NaOH solution.

Procedure:1. Pipette out 10 ml of the milk sample into a conical

flask. To it, add 20 ml distilled water and add 3 to 4 drops of alcoholic solution of phenolphthalein. Shake the mixture thoroughly.

2. Fill a burette with 0.1 N NaOH solution. Titrate the milk solution, shaking all the time, until a permanent faint pink colour appears.

3. Calculate how many millilitres of the alkali solution were used to neutralize the 10 millilitres of milk solution. Then determine the millilitres required for neutralizing 100ml of the sample. This will be the acidity of the milk in degrees on

the Turner scales.

Observations:Concentration of NaOHVolume of milk taken = 10mlVolume of water added to the milk = 20ml

S.No.

Initial Reading (ml)

Final Reading

(ml)

Volume of NaOH

consumed1.2.3.

0.010.020.0

8.218.228.2

8.28.28.2

Calculations:

10ml of milk is neutralized by 8.2 ml of NaOH100ml of milk is neutralized by (8.2/10) x 100

= 82ml NaOH

Result: Acidity of Milk is found to be 82 degrees on the Turner Scale.

II. DETERMINATION OF THE QUANTITY OF MILK SUGAR

Apparatus: Beakers, test tubes, funnel, filter paper and burner

Chemicals: Milk, 10% acetic acid

Procedure:1. Take 20ml of fresh milk and weigh it.2. To it, add 10% acetic acid to precipitate all the

proteins and filter the solution. Filtrate contains sugar.

3. Evaporate the filtrate and take the weight of the residue. Residue is milk sugar.

Observations:

Weight of 20ml of Milk = 18.7gWeight of the residue (milk sugar) = 0.27gPercentage of sugar in Milk = (0.27/18.7) x 100

= 1.44%

Result: The percentage of the milk sugar present in the sample is 1.44%

RESULT

Hence, these simple tests give a complete description of milk.

The qualitative analysis of milk clearly indicates the presence of carbohydrates, proteins, fats, starch and microelements (phosphates) in the milk.

The quantitative analysis of milk gives us an idea of the acidity of milk. Also the quantity of milk sugar present in milk is calculated.