From a nutritive point of view, the important components of milk are the fats, proteids and sugar, but especially in the nourishment of the young the value of lime and phosphoric acid must be remembered. The mean composition of the most important milks, as determined by recent analyses, is given below:
| Water. Per cent. | Sugar. Per cent. | Proteids. Per cent. | Fat. Per cent. | Ash. Per cent. | |
|---|---|---|---|---|---|
| Cow | 86.90 | 4.80 | 3.60 | 4.00 | 0.70 |
| Human | 88.75 | 6.00 | 1.50 | 3.45 | 0.30 |
| Goat | 85.70 | 4.45 | 4.30 | 4.75 | 0.80 |
| Ass | 89.50 | 6.25 | 2.00 | 1.75 | 0.50 |
| Mare | 90.75 | 5.70 | 2.00 | 1.20 | 0.35 |
| Sheep | 80.80 | 4.90 | 6.55 | 6.85 | 0.90 |
The mean composition of milk, as given by Watts and König, is given in the following tables:
| Watts. | ||||||
|---|---|---|---|---|---|---|
| Water. | Solids. | Proteids. | Fats. | Sugar. | Mineral Salts. | |
| Woman | 87.65 | 12.35 | 3.07 | 3.91 | 5.01 | 0.17 |
| Ass | 90.70 | 9.30 | 1.70 | 1.55 | 5.80 | 0.50 |
| Cow | 86.56 | 13.44 | 4.08 | 4.03 | 4.60 | 0.73 |
| Goat | 86.76 | 13.24 | 4.23 | 4.48 | 3.91 | 0.62 |
| Sheep | 83.31 | 16.69 | 5.73 | 6.05 | 3.96 | 0.68 |
| Mare | 82.84 | 17.16 | 1.64 | 6.87 | 8.65 | |
| König. | |||||
|---|---|---|---|---|---|
| Water. | Fat. | Casein and albumin. | Milk Sugar. | Ash. | |
| Woman | 87.41 | 3.78 | 2.29 | 6.21 | 0.31 |
| Mare | 90.78 | 1.21 | 1.99 | 5.67 | 0.35 |
| Ass | 89.64 | 1.63 | 2.22 | 5.99 | 0.51 |
| Cow | 87.17 | 3.69 | 3.55 | 4.88 | 0.71 |
The average composition of 120,540 samples of cow milk, as determined by analysis, extending over a period of eleven years, was found by Vieth to be as follows:[402]
| Per cent. | |
| Total solids | 12.9 |
| Solids not fat | 8.8 |
| Fat | 4.1 |
The quantity of solids and fat in milk is less after longer than after shorter periods between milkings.
The quantity of solids and fat in cow milk is less in the spring than in the autumn.
The chief organic acid naturally present in milk is citric, which exists probably in combination with lime.