CHEESE AND Cheese is the curd of milk, including princi pally the casein and fat, coagulated, cooked, drained and pressed into solid form. Nearly all cheese is made from cows' milk, and origi nally it was a product of the farm. Now by far the greater portion is made in factories especially fitted for the purpose. The standard factory-made American cheese is practically identical with the English cheddar cheese, and is often so called.
In the manufacture of cheese a milk rich in fat is preferred, the cheese being nearly all fat and casein. By artificial souring of the milk coagulation is produced, so that the whey or watery part may be separated from the curd. The curd is the raw material operated on; the casein is a proteid substance that may be com pared to lean meat, and is coagulated by acid. It is that part of the curd that remains when the fat, sugar and ash are extracted. The first process of manufacture is to heat the milk (preferably sweet milk) to about 84° F. It is then tested with rennet for ripeness. A gradu ated cup provided with a fine hole in the bot tom is filled with milk and a little rennet added. Rennet, in its commercial form, is a preserved extract from the fourth stomach of a calf. Being of a peptic character it tends to coagulate the milk, and if the milk in the cup coagulates in from 17 to 20 seconds it is sufficiently ripe for treatment. Enough rennet • is then added to the supply of milk to coagulate the whole in 25 or 30 minutes. The proportions vary with conditions, but about four ounces of rennet extract to 100 gallons of milk is perhaps an average quantity. When the milk is coagulated the solid portion or curd in tit( i vat is separated from the watery portion, by allowing the latter to drain off. This waste usually becomes food for pigs. Gang knives are then brought into use to cut the curd into cubes of a third of an inch or more, the knives being set a little less than half an inch apart and passed through the curd horizontally and perpendicularly. Af ter cutting, the curd is gently agitated to pre vent settling. This allows the curd to shrink and tends to expel a portion of the whey. The stirring may be done with a curd-rake, but factories more commonly employ what is termed an automatic curd-agitator, which is attached to the vat and driven by steam power.
The mass of curd is next heated very slowly to about 92° F. This cooking process may con tinue several hours, lasting until the operator finds that the curd will string about a quarter to a third of an inch on a hot iron. The whey is then drawn off. The curd is next turned and piled, to rid it of the excess of moisture. When deemed sufficiently solid it is ground and salted. The grinding may be done in one of several kinds of mills, a common form having two cylinders with teeth rotating toward each other, which operation picks the curd to pieces.
After grinding, the curd—or cheese, as it may now be called — is dipped and put into hoops to give it form for pressing. Common sizes of hoops are 14% X 10 and 13% X 6 inches. An iron bandage or rim is placed about the hoop to give it solidity, and a cloth wrapped about it to keep the cheese together and secure cleanliness. Pressure is then ap plied, at first lightly, and then increased, the cheese being usually turned over during the operation. The pressure is maintained for 16 to 18 hours, after which the cheese is ready to be cured.
Curing-rooms are built both above and be low ground, the latter being preferred as being easier to maintain at a cool temperature. High temperature is very deleterious to cheese, di minishing its value by melting and leaking of fat, while the texture and flavor are also impaired. A temperature below F. should always be maintained in the curing-room, and 40° is better. Ventilation must be provided, and the usual arrangement is an upright draft pipe, run high enough to catch the wind, and with a vane at the top to turn the mouth of the funnel to the wind. The process called ripening takes place in the curing-room, deter mining the particular flavor of the cheese. The ripening is caused by bacteria, as is proven by making cheese from sterilized milk, in which case it retains the flavor of new-made cheese for a very long period. Dairy bacteriologists are endeavoring to isolate the different species of cheese bacteria, that they may be cultured and incorporated with the milk in starting the cheese-making. In this way the maker would be certain of securing a particular flavor for his cheese, whereas now it is a matter largely of chance as to what bacteria predominate.