नमस्कार विद्यार्थी मित्रांनो Detection of commonly used adulterants in milk हे प्रॅक्टिकल Experiments to be performed - PART A मधील आहे. याचाच अर्थ तुम्हाला हे प्रॅक्टिकल Exam मध्ये Examiner ला Performe करून दाखवायचे आहे. म्हणूनच प्रॅक्टिकल Exam च्या दृष्टीने हे Experiment अतिशय महत्त्वाचे आहे. या ब्लॉग मध्ये आपण Practical Book मधील या Experiment Number - 13 ची उत्तरे पाहणारं आहोत. ही उत्तरे काळजीपूर्वक वाचून आपल्या Practical Book मध्ये लिहा किंवा तुमच्या कॉलेजमधील संबंधित विषय शिक्षकांची मदत घ्या.
13. Detection of commonly used adulterants in milk.
The most common adulterants found in milk are urea, insecticides, NaHCO3, vegetable oil, sucrose, starch, etc.
Aim :- To detect the presence of excess water added to the milk by using a lactometer.
Requirements :- Lactometer, measuring cylinders (500 ml capacity), thermometer and milk samples (minimum 3, preferably raw milk, of same animal source cow/buffalo)
Theory :- Animal husbandry plays a major supporting role in the rural economy. Milk collection centers and cooperative societies, play an integral role in delivering the milk from the cowsheds to the customers.
Addition of water to milk can be a big problem. Hence the water content of the milk is checked at many levels, before it reaches the customer. Pure milk has a specific gravity of 1-032; addition of water to it reduces this value. FAO (Food and Agriculture Organization of the United Nations) suggested that the standard specific gravity of milk ranges between 1.026 to 1.032 g/ml.
Principle :- Use of lactometer is a most widely used method for detection of specific gravity of milk. A lactometer is a hydrometer with a limited scale (close to the range of the specific gravity of milk). Lactometer works on the principle of fluid displacement.
A lactometer is an instrument sensitive to temperature, hence, the temperature of the milk sample must always be noted along with the reading of the lactometer. Temperature calibration must be either added or subtracted from the reading on the lactometer, to get the final specific gravity of the milk sample.
Figure :-
 |
| Fig. Experimental set up |
Procedure :-
1) Prepare three measuring cylinders (500 ml capacity) and label them 1,2,and 3.
2) Pour milk samples gently, in each measuring cylinder.
3) Let the lactometer sink gently in the milk sample.
4) Read and record the last lactometer degree reading (°L) just above the surface of milk.
5) Note down the temperature of each milk sample by using the thermometer.
6) If the temperature of milk is different from that of the calibration temperature of the lactometer (20°C), then calculate temperature correction.
7) For every 10°C above the calibration temperature, odd 0.2 °L to the actual lactometer reading.
8) For every 10°C below the calibration temperature, subtract 0.2 °L. from the actual lactometer reading.
Observation table and Calculation :-
| Sample | Milk temperature | Lactometer reading | Correction | Final reading |
|---|---|---|---|---|
| E.g. 1 | 17 °C | 30.6 °L | -0.6 °L | 30.0 °L |
| E.g. 2 | 23 °C | 30.6 °L | +0.6 °L | 29.4 °L |
| Sample 1 | 21 °C | 31.6 °L | +0.4 °L | 31.2 °L |
| Sample 2 | 17 °C | 29.1 °L | -0.6 °L | 29.7 °L |
| Sample 3 | 23 °C | 28.7 °L | +0.6 °L | 28.1 °L |
• For calculation of the specific gravity of the milk samples, we take the final reading from the above table and write 1.0 before it. (lactometer reading represents only the second and third decimal place).
| Sample | Final reading | Specific gravity of milk sample |
|---|---|---|
| E.g. 1 | 30.0 °L | 1.030 |
| E.g. 2 | 29.4 °L | 1.029 |
| Sample 1 | 31.2 °L | 1.031 |
| Sample 2 | 29.7 °L | 1.030 |
| Sample 3 | 28.1 °L | 1.028 |
Result :-
• Specific gravity of milk sample 1 is 1.031
• Specific gravity of milk sample 2 is 1.030
• Specific gravity of milk sample 3 is 1.028
Questions
1. What is the principle of fluid displacement?
Ans :- The principle of fluid displacement, based on Archimedes' principle, states that any body fully or partially immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the body. This buoyant force acts in the upward direction at the center of mass of the displaced fluid.
2. How can the specific gravity of milk be adjusted to acceptable limits after it has been adulterated with water?
Ans :- The specific gravity of milk, typically ranging from 1.028 to 1.033 kg/L at 15°C or 20°C, is influenced by its protein and fat content. Since the specific gravity of fat is 0.93 kg/L and the specific gravity of water is 1.0 kg/L, adjusting the specific gravity of milk after it has been adulterated with water involves correcting for these variations. This adjustment can be achieved by adding concentrated milk or cream to restore the milk's original specific gravity.
3. Which chemicals when added to milk, result into its adulteration?
Ans :- Chemicals that can adulterate milk include urea, insecticides, baking soda, vegetable oil, sucrose, and starch.
4. What are the other methods for detecting excess water, added to the milk?
Ans :- Other methods for detecting excess water in milk include:
1. Flow Test: Place a drop of milk on a slanted surface. Pure milk flows slowly and leaves a mark, while milk adulterated with water flows quickly and leaves no mark.
2. Iodine Test: Add a few drops of iodine solution to the milk. Watered-down milk often shows a different color reaction compared to pure milk, indicating dilution.
Multiple Choice Questions
1. The specific gravity of pure milk is...g/ml.
a. 1.032
b. 2.432
c. 0.123
d. 0.982
Ans :- a. 1.032
2. The instrument used for detection of specific gravity in milk is...
a. Spirometer
b. Galvanometer
c. Lactometer
d. Altometer
Ans :- c. Lactometer
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