Experiments of Chemistry of Milk

EXPERIMENT - 1
Objective
Identification of Glassware/apparatus used in Dairy Chemistry Laboratory.
Apparatus
Test tube, Beaker, Measuring Cylinder, Conical Flask, Volumetric Flask, Funnel, Pipette, Glass Rod, Spatula, Dropper, Aluminium Dish, Silica Crucible, Test Tube Stand, Burette, Burette Stand, Gerber Milk Butyrometer, Lactometer, Stalagnometer, Ostwal Viscometer, Specific Gravity Bottle.
(a) Test Tube
It is used for holding small amount of chemical for conducting chemical reaction.
(b) Measuring Cylinder
It is used for measuring different quantities of chemical/reagents.
(c) Beaker
It is used for holding, storage and for preparation of chemicals and is also used for heating and boiling purpose.
(d) Conical Flask
It is used for holding/preparation and storage of chemicals and reagents.
(e) Volumetric Flask
This is used for preparation of segments where exact/definite volume of reagents required.
(f) Funnel
It is used for transferring of chemical reagents.
(g) Glass Rod
It is used for mixing of differet reagents of solid chemicals.
(i) Spatula
This is used for transfering small quantity/quantities of solid chemicals.
(j) Dropper
It is used for dispersing liquid reagents drop by drop.
(k) Aluminium Dish
It is used where moisture is to be removed from the samples.
(l) Silica Crucible
It is used for determining the ash content of milk and milk products.
(m) Test Tube Stand
It is used for holding the the test tube.
(n) Burette Stand
It is used to hold the burette.
(o) Gerber Milk Butyrometer
It is used for the analysis of fat in milk samples.
(p) Lactometer
It is used for the calculation of total solid and density of milk.
(p) Stalagnometer
It is used to calculate surface tension in milk.
(r) Specific Gravity Bottle
It is used for calculation of specific gravity of milk.
(s) Ostwald Viscometer
It is used for calculation of viscosity in milk.

EXPERIMENT - 2

Objective
Identification of commonly used instrument in Dairy Chemistry Laboratory.
Apparatus
Gerber Centrifuge, Soxhlet Apparatus, Dessicator, Weighing Balance, Water Distillation Unit, Muffle Furnace, Spectro Photometer, pH Meter, Hot Air Oven, Kjeldahl Digestion Unit, Water Bath, Kjeldahl Distillation Unit.
(a) Gerber Centrifuge
It is used for centrifugation of gerber butyrometer for estimation of fat.
(b) Soxhlet Apparatus
It is used for determination of fat.
(c) Dessicator
This instrument is used for cooling the samples under air tight conditions.
(d) Weighing Balance
It is used for weighing of samples, reagents, etc.
(e) Water Distillation Unit
This instrument is used for preparation of distilled water.
(f) Muffle Furnace
It is used for estimation od ash content in milk and milk products.
(g) pH Meter
It is used to measure pH accurately.
(h) Water Bath
It is used for indirect heating of samples of chemical reagents.
(i) Spectro Photometer
This instrument is used for taking optical density of biological solution.
(k) Hot Air Oven
It is used for determination of toatal solid and moisture content of the dairy products.
(l) Kjeldahl Digestion Unit
This instrument is used for estimation od protein in milk and its product.

EXPERIMENT - 3

Objective
To determine the pH of milk using pH metre.
Introduction/Principle
pH may be defined as the negative logarithm of H ion concentration. pH below 7 indicates acidic side of pH scale, pH above 7 indicates alkaline side of pH scale whereas pH 7 is the netral pH. Normal pH of milk varies from 6.6 to 6.8 pH above 6.8 indicates alkaline condition of milk which might be due to over neutralization of milk or milk have been derived from mustitic animal. pH below 6.6 indicates an increase in acidity of milk which might be due to the increased growth of microoraganism in milk.
Matreials Required
pH Meter, Beaker, Wash Bottle, Milk Sample.
Procedure
1. Take 50 ml of milk in a beaker and adjust the temperature to 20 degree Celcius.
2. Switch on the pH meter.
3. Dip the electrode of the pH meter into the sample.
4. Note the pH reading from the display of the pH meter.
Observation
pH of the given milk sample is 6.80.
Result
pH of the given sample of milk is 6.80.

EXPERIMENT - 4
Objective
To determine the titratable acidity of milk.
Apparatus Required
Burette, Pipette, Beaker, Flask.
Chemicals Required
0.1N NaOH Solution, Phenolphathelene Indicator, Milk Sample.
Theory
Titration is the process of obtaining the end point of an unknown solution of a chemical substance which is placed in burette and allowed to fall drop-by-drop on conical flask containing known solution with acid/basic indicator in it. With noting down of 3-4 readings we come to a approximate reading of acidity/basicity of unknown solution. There are two types of acidity in milk:
(a) Natural Acidity
(b) Developed Acidity
The summation of natural acidity and titratable acidity is known as Titratable acidity of given milk sample. Natural acidity due to constituents like caseim, aluminium citrate, phosphate and carbon dioxide. Fresh milk when drawn from udder is neutral to litmus. After keeping the fresh milk at room temperature for sometimes lactose is broken down by micro-oraganisms in lactic acid. This acidity is called developed acidity.
Reaction
CH3CH(OH)COOH + NaOH --> CH3CH(OH)COONa + H2O
Procedure
1. Milk sample is pipetted in 100 ml of conical flask.
2. 3-5 drops of phenophthalein indicator is added to it.
3. Then slowly add 0.1N NaOH from the burette until the colour changes to faint pink.
4. Note the volume of 0.1N NaOH required for titration.
Observation
Volume of milk taken = 10 ml.
Volume of 0.1N NaOH required for titration = 3.9 ml.
Calculation
1000 ml of 1N NaOH = 90 grams of lactic acid.
1 ml of NaOH = 0.009 grams of lactic acid.
V ml of NaOH = 0.009 x N
10 ml of milk contain= 0.009 x N x 3.9.
100 ml of milk contain = 0.009/10 x 100 x 3.9.
Total acidity of milk sample = 0.351.
Result
The titratable acidity for the given sample of milk is 0.0351% lactic acid.

EXPERIMENT - 05

Object
Clot on Boiling Test [COB Test].
Introduction
Milk with highly developed acidity clots on boiling. A positive COB Test indicates the formation of curd or flakes on curdling in case of normal milk. A COB positive milk should be rejected and such milk are unsuitable for processing as they will clot upon heat treatment.
Materials Required
Milk samples test tube, test tube holder, water bath.
Procedure
1. Take 5 ml of milk in a clean  test tube.
2. Place the test tube in the boiling water bath for 5 minutes.
3. Remove the test tube and observe clotting on the sides and bottom of test tube.
Observation
For sample A, COB =
For sample B, COB =
Result
The given sample of milk (sample A) in COB ____ and sample B's COB _____.

EXPERIMENT - 06
Object
Alcohol Test
Introduction
Alcohol test determines the suseptibility of milk to coagulation due to developed acidity or due to salt imbalance caused due to developed acidity. A positive alcohol test indicates formation of flakes or curd waheras normal milk shows no curdling. Alcohol test is especially important for the manufacturing of milk for sterilization process. It also detects abnormal milk such as colestrum or milk with high salt content.
Material
Petri Dish, Test Tube, Pipette, 68% Ethyl Alcohol.
Procedure
1. Take 5 ml of milk in a petri plate or test tube.
2. Add an equal amount of 68% ethyl alcohol.
3. Mix well and observe for flakes, curd or clot.
Observation
For sample A, Alcohol Test =
For sample B, Alcohol Test =
Result
For the given sample of milk (sample A) Alcohol Test is ____ and for sample B Alcohol Test is _____.

EXPERIMENT - 07
Objective
Determination of total solids in milk by ( this contains content, please leave a space of hlaf-line )
Introduction
A known weight of milk sample in dried to constant weight of milk sample is dried to constant weight in an oven and the less of weight is equal to the moisture content in the milk.
Materials Required
Aluminium flat bottom dish with lid, weighing balance, steam bath, hot air oven, dessicator, milk samples.
Procedure

1. Weigh a clean dry and empty aluminium dish with lid.
2. Pipette about 5 ml milk into the dish and weigh again with its lid on.
3. Place the dish uncovered on a boiling water bath till the liquid portion dries off.
4. Wipe the base of aluminium dish and place the aluminium dish with its lid in the hot air oven maintained at 100 (plus minus, please denote the sign) 5 degree Celcius for about 4-5 hours.
5. Transfer it to the dessication, cool and weight.

Observation
Weight of empty dish (w) =
Weight of aluminium dish + milk before drying (w1) =
Weight of aluminium dish + milk after drying (w2) =
Calculation
Total solid percentage = (w2 - w/w1 - w)100.
Moisture Percentage = 100 - TS%
Result
The total solid in the given milk sample is

EXPERIMENT - 08
Objective
Determination od ash content in milk.
Introduction
Salt content of milk is often expressed in terms of ash content and is obtained as non-combustible matter in milk. Heating of milk at higher temperature decomposes organic matter and soluble organic salts are left behind in the form of ash. The term salt refers to all chemical elements excluding hydrogen ion and hydroxyl ion that are present as ion or in equillibrium with ions.
Material Required
Milk samples, silica crucibles, dessicator, muffle furnace, hot plate,
Procedure

1. Weigh an empty silica crucible.
2. Weigh 5 gram of milk into the pre weighed crucible and weigh again.
3. Evaporate the sample to dryness by placing it on hot plate.
4. Plate the crucible in a muffle furnace maintained at 550 degreee Celcius for 4-5 hours.
5. Place the crucibles in dessicator and let it cool down.
6. Take the weigh of cooled crucible.

Observation
Weight of emptycrucible (w) =
Weight of milk sample + crucible (w1) =
Weight of milk sample + crucible after ashing (w2) =
Calculation
Ash percentage by weight = (w2 - w/w1 - w)100 =
Result
Ash content of given sample of milk is

EXPERIMENT - 09
Objective
Determination of protein content in milk by Pyne's Method (Formal Titration).
Introduction
The protein content in milk can be estimated rapidly by means of formal titration. Formaldehyde in excess readily combined with free i.e., unprotonated amino groups of amino acids to give methylol derivatives. this reaction causes an isoelectric amino acids to lose a proton from the +NH3 groups of zwitter ion form. The proton that is librated can be titrated within alkali and multiplied by Pyne's constant (x 1.7) to give protein content of milk sample. Addition of potassium oxalates before titrating helps to eliminate all calcium as insoluble calcium oxalates from calcium caseinate complex.
[ Please, leave 2 lines to write down the reaction ]
Materials Required
Conical flask, Potassium oxilate (salt), milk sample.
Procedure

1. Take 10 ml of milk into a 100 ml of conical flask.
2. Add 1 ml of phenopthalein indicator solution and mix well.
3. Add 0.4 ml saturated potassium oxalate, mix well and then leave aside for about 2 minutes.
4. Titrate the milk to faint pink colour by using standard 0.1N NaOH solution from two burette.
5. After the end point is reached add 2 ml of neutral formaldehyde solution.
6. Titrate again 0.1N NaOH to end point (faint pink colour).
7. Record the volume of NaOH required for second titration only.

Observation
Volume of 0.1N NaOH used for second titration (V) = 2.6 ml.
Calculation
Percentage Protein = 1.7 x V = 4.42%
Result
The protein content in the given milk sample by Pyne's method is 4.42%.

Experiment 12