Skim milk is prepared by the removal of some of the fat from whole milk. This skim milk is found to contain 90.5% water, 3.5% protein, 5.1% carbohydrate, 0.1% fat and 0.8% ash. If the original milk contained 4.5% fat, Calculate its composition assuming that fat only was removed to make the skim milk and that there are no losses in processing.

Correct Answer: Fat = 4.5%, Water = 86.5%, protein = 3.3%, carbohydrate = 4.9%, ash = 0.8%
Basis: 100 kg of skim milk. This contains, therefore, 0.1kg of fat. Let the fat which was removed from it to make skim milk be x kg. Total original fat = (x + 0.1) kg Total original mass = (100 + x) kg and as it is shown that the original fat content was 4.5% so, (x+0.1)/(100+x) = 0.045 where = x+0.1 = 0.045(100+x) x = 4.6 kg So the composition of the whole milk is then fat = 4.5%, water = 90.5/104.6 = 86.5%, protein = 3.5/104.6 = 3.3%, carbohydrate = 5.1/104.6 = 4.9% and ash = 0.8%.