Another method of separating artificial coloring matter has been proposed by Martin.[512]
A method of determining the relative amount of butter color has been worked out by Babcock.[513]
EXAMINATION OF CHEESE.
510. Composition Of Cheese.—Pure cheese is made from whole milk by precipitating the casein with rennet. The precipitated casein carries down also the fat of the milk and a little lactose and whey remain incorporated with the cheesy mass. The ingredients of cheese are therefore those of the whole milk less the greater part of the whey, id est, milk sugar, lactalbumin, globulin, soluble mineral matters and water. In the conversion of the crude precipitate noted above into the cheese of commerce, it is subjected to a ripening process which is chiefly conditioned by bacterial action. It is not possible here to enter into a discussion of methods of isolating and identifying the bacteria which promote or retard the ripening process.[514] As a rule, about a month is required for the curing process, before the cheeses are ready for boxing and shipment. The most important changes during ripening take place in the proteid matter, which is so altered as to become more palatable and more digestible as a result of the bacterial activity.
The percentage composition of the principal cheeses of commerce are shown in the following table:[515]
| Water, Per cent. | Casein, Per cent. | Fat, Per cent. | Sugar, Per cent. | Ash, Per cent. | |
|---|---|---|---|---|---|
| Cheddar | 34.38 | 26.38 | 32.71 | 2.95 | 3.58 |
| Cheshire | 32.59 | 32.51 | 26.06 | 4.53 | 4.31 |
| Stilton | 30.35 | 28.85 | 35.39 | 1.59 | 3.83 |
| Brie | 50.35 | 17.18 | 25.12 | 1.94 | 5.41 |
| Neufchatel | 44.47 | 14.60 | 33.70 | 4.24 | 2.99 |
| Roquefort | 31.20 | 27.63 | 33.16 | 2.00 | 6.01 |
| Edam | 36.28 | 24.06 | 30.26 | 4.60 | 4.90 |
| Swiss | 35.80 | 24.44 | 37.40 | 2.36 | |
| Full cream, | 38.60 | 25.35 | 30.25 | 2.03 | 4.07 |
| (mean of 143 analyses) |
It is evident that the composition of the cheese will vary with the milk from which it is made and the manipulation to which it is subjected. A good American green cheese made from milk of the composition noted below will have the composition which is appended.[516]
Table Showing Mean Composition of
Milk and Cheese Made Therefrom.
| Milk. | Cheese. | |||
|---|---|---|---|---|
| Per | cent. | water | 87.38 | 36.70 |
| ” | ” | fat | 3.73 | 34.18 |
| ” | ” | proteids | 3.13 | 23.44 |
| ” | ” | sugar, ash etc. | 5.76 | 5.68 |
From the above it is seen that in full milk cheese the ratio of fat to casein is 1.46: 1, and to solids not fat 1.17: 1. This is a point of some importance in judging the purity of a cheese. When the full milk of a mixed herd is used the percentage of fat in a cheese will always be considerably higher than that of casein.