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Determination of Melting Point of Fats and Oils

In this determination of melting point of fats and oils post we briefly summarise about: principle, reagents requirements, melting point of oil and fat procedure, result, application and limitations of melting point of fats and oils.

Determination of Melting Point of Fats and Oils

Melting point of fat is and melting point of oil is ranges between 22 and 40°C. The composition of fatty acids determines the melting point. Oils and fats are chiefly mixtures of triglycerides. They do not exhibit either a definite or sharp melting point.

Therefore the melting point of oil and fat does not imply the same characteristics that it does with pure crystalline substances. Fats pass through a stage of gradual softening before they become completely liquid. The melting point is therefore defined by the specific conditions of the method by which it is determined.

Melting Point Of Oil and Fat

Melting point of oil and fat or any other compound is the temperature at which the oil or fat softens or becomes sufficiently fluid to slip or run as melting point of oil and fat determined by the open tube capillary slip method.

Requirements

1. Apparatus

2. Melting point tubes

3. Thermometer

4. Beaker with a side tube heating

5. Heat source

Procedure

1. Melt the sample and filter it through a filter paper to remove any impurities and last traces of moisture. Make sure that the sample is absolutely dry and Mix the sample thoroughly to analysis of melting point of oil and fat.

2. Introduce a capillary tube into the molten sample, so that a column of the sample, about 10 mm long, is sucked into the tube.

3. Dip at least 3 clean capillary tubes in the completely liquid sample so that the sample rises about 10 mm high in tubes.

4. Chill the sample at once by holding the ends of the tubes that contain the sample against a piece of ice until the fat solidifies. Place the tube in a small beaker and hold it in a refrigerator at 4°C to 10°C for 16 hours.

5. Remove the tube from the refrigerator and attach with a rubber band to the thermometer bulb, so that the lower end of the capillary tube and the thermometer bulb are at the same level.

6. Suspend the thermometer in 600 mL beaker of clear distilled water. The bottom of thermometer is immersed in the water to the immersion mark.

7. Take water at 10°C in the ‘Thiele’ tube and immerse the thermometer with the capillary tube containing the sample of fat.

8. Gradually increase the temperature by heating at the side-tube of the Thiel Tube at the rate of 2°C per min, till the temperature reaches 25°C, and thereafter at the rate of 0.5°C per minutes Note the temperature of the water when the sample column begins to rise in the capillary tube.

9. Report the average of two such separate determinations as the melting point of oil and fat, provided that the readings do not differ by more than 0.5°C. 

Further Readings

Reference

  1. https://www.aocs.org/attain-lab-services/methods/methods
  2. https://static1.buchi.com/sites/default/files/Slip_Melting_Point_Palm_Stearin.pdf