total fat analysis in milk using the gerber method

Object Required

milk,sulfuric acid,amyl alcohol

Principle

the Gerber Method is a primary and historic chemical test to determine the fat content of milk and other substances.Fat is the most important constituent of milk as it is used as a basis for fixing the purchase and sale price of milk. It helps to detect adulteration like watering and skimming of milk. Gerber’s method commonly used in Europe and in India.

Theory

Dr. N Gerber of Zurich Switzerland invented this method in the year 1892-1895. In this test H2SO4 is used to increase specific gravity of milk serum which makes greater difference between milk serum and fat globules. It also destroys stickiness of milk by dissolving all the SNF. The free fat globules rise to the surface by subsequent application of centrifugal force to this mixture and heat produced due to mixing of acid and milk, causing melting of fat. It facilitates the fat particles to come to the surface freely.

The specific gravity of fat is 0.9 and that of acid milk mixtures is 1.43. This situation promotes complete separation of fat when proper centrifugal force is applied.

Due to application of centrifugal force lighter substances (Butter fat) are thrown towards centre and rest of serum portion that is heavier is thrown towards the pheriphen.

Addition of amyl alcohol helps for separation of fat from the milk acid mixture and also prevents the charging of fat and sugar by the H2SO4.

Conclusion

1. Put the clean and dry butyrometer in a butyrometer stand (Camlab part no. 1162195) with open mouth upwards. 2. Run 10 ml of sulphuric acid with the tilt measure in the butyrometer. 3. Pipette out 10.75 ml of milk sample gently by the side of butyrometer, whose temperature is about 15-21 degrees C. 4. Pour 1 ml. of amyl alcohol with tilt measure. 5. Stopper the butyrometer with the help of lock stopper using regulating pin/guiding pin. 6. The tube is well (mixed) shaken till mahogany red colour is obtained. Keep the butyrometer in hot water bath till it attains 15-21 degrees C and the butyrometer are placed in the centrifuge at 1100 rpm for 4 minutes. 7. Take out the butyrometer in an upright position with the stopper end down wards. 8. Keep the butyrometer in hot water bath at (65 degrees C) for some time. 9. Note the reading. Reading should be taken from bottom of the fat column to lower border of meniscus on the scale.

Published Date

28 Feb, 2018