EXPERIMENT 48: SEPARATION OF CURD AND WHEY—Again heat the contents of the test tube of Experiment 47, turn the mixture into a cheese-cloth, and press the cloth until the mixture is dry. Examine the material left in the cloth. How does it differ from ordinary cheese in color and texture? In cheese making what names are given to the solids and liquids of clotted milk?
Cheese is prepared for the market in a way somewhat similar to that shown in Experiments 47 and 48, except that it is colored, salted, pressed into shape, and allowed to ripen. While ripening, changes take place in the ingredients of cheese which develop characteristic flavors and make the cheese firm.
There are two general classes of cheese,—hard cheese and soft cheese. A hard cheese commonly known as "American Cream Cheese" is generally used in this country.
ACTION OF RENNIN IN DIGESTING MILK.—The rennet or junket used to clot the casein of the milk is obtained from the digestive juices of the stomach of a calf. An enzyme called rennin exists in the gastric juice of the human stomach also. When milk is digested, it is first clotted by the enzyme in the stomach.
EXPERIMENT 49: EFFECT OF ACID ON MILK.—Add a few drops of vinegar to warm milk in a test tube. What is the result? What substance in the milk has been curdled by the acid?
To what substance in milk is its sweet taste due? Into what has this substance changed when milk sours? What causes the change in this material (see Care of Milk)? Knowing the effect of acid on milk, explain the clotted condition of sour milk.
JUNKET "CUSTARD"
1 quart milk 1/4 cupful sugar 1 teaspoonful vanilla 1 tablespoonful liquid rennet or 1 junket tablet Powdered cinnamon or nutmeg
Heat the milk in a double boiler until it is lukewarm only; do not heat it to scalding temperature. Test milk for lukewarm, i.e. body temperature, by letting a drop fall on the wrist. If the milk "feels like the wrist"—neither warmer nor colder—it is lukewarm in temperature. If a junket tablet is used, crush it. Add the sugar, vanilla, and rennet or junket, and stir until dissolved. Pour into a glass dish and stand in a warm place until it thickens. Then set the Junket "Custard" in a cool place. When cold, sprinkle with a little cinnamon or nutmeg, and serve with cream.