Determination of Casein Content in Different Milk
Samples
Aim
To determine and compare the percentage of casein protein in different milk samples by acid
precipitation method.
Principle
Casein in milk precipitates at its isoelectric pH (~4.6). Acidifying milk with acetic acid causes curd
formation which is filtered, dried and weighed to calculate casein percentage.
Apparatus
Beakers, conical flasks, measuring cylinders, pH paper, filter paper, funnel, oven, balance, glass
rod.
Chemicals
Milk samples (cow, buffalo, goat, toned, skimmed), acetic acid, distilled water.
Procedure
1. Measure 10 g of milk sample.
2. Warm slightly and add acetic acid dropwise until curd forms (pH 4.6).
3. Filter the precipitated casein.
4. Wash with distilled water.
5. Dry the precipitate to constant weight.
6. Weigh and calculate percentage casein.
Observation Table (Format)
Sample | Mass of Milk (g) | Mass of Casein (g) | % Casein
Cow | 10 | 0.32 | 3.20%
Buffalo | 10 | 0.42 | 4.20%
Goat | 10 | 0.36 | 3.60%
Toned | 10 | 0.20 | 2.00%
Skimmed | 10 | 0.15 | 1.50%
Conclusion
Buffalo milk contains the highest casein content while toned and skimmed milk have lower
percentages due to processing.
