Q. Evaluate percentage Fat Content in Milk?

The fat content in milk can be determined through various procedures as:

Direct determination of fat by extraction with ether - Adam's coil method

• Separation of fat by acid/ alkali treatment and its subsequent removal by ether-Werner-Schimdt and Gottleib method

• Separation of fat by chemical means followed by centrifugation - Gerber method

The main principle behind the fat determination is  protein precipitation, which is further dissolved in acid to free fat globules. In some methods, amyl alcohol is also added to produce difference in the surface tension of fat globules and the supporting liquid, thus causing the aggregation and separation of fat.

As Gerber method gives fast results, thus, it is used in the dairy plants as a platform test for checking the quality of milk. In this test, fat is dissolved in hot amyl alcohol and its separation from heavy acid solution is affected by subjecting the mixture to centrifuging. In Gerber method, 10 ml of conc. H2SO4 is added into the gerber tube. 1 ml of amyl alcohol is added in this tube. 10.94 ml of the milk sample is added and the tube is stoppered. The tube is then inverted twice or thrice and shaken briskly to mix the ingredients. The tube is then centrifuged for 3 min at 1000 rpm to get the reading of fat in the stem of the tube.