EFFECT OF THE SALT AND
ICE MIXTURE ON TEMPERATURE
Make a brine one part salt to ten parts of water by weight. With part of this fill the can of a hand freezer two thirds full just as though it were an ice cream mix which you were going to freeze. Record the temperature of this brine.
Trial 1. Using a mixture of one pound of salt to 10 lbs. of crushed ice, try freezing the brine in the freezer can. Turn 10 minutes, keeping the freezer can well covered with the ice and salt mixture. Open and record the temperature of the brine in the can.
Trial 2. Empty the freezer can and tub and refill the can with more of the brine used in Trial 1. Be sure to have it the same temperature. Using a salt and ice mixture of the same proportions, pack the tub again and in addition add enough cold water so that it starts to run from the overflow hole in the tub. Turn the freezer 10 minutes, recording the temperature of the brine flowing from the overflow hole every 2 minutes. Be sure to keep the ice-salt-water mixture in the tub well mixed by punching with a stick such as a sawed-off broom handle. Again record the temperature of the brine in the can. Why does it differ from what it was in Trial 1?
Trial 3. Repeat Trial 2, except use a mixture of salt and ice one to six instead of one to 10. Record results.
Trial 4. Repeat Trial 3 but do not mix the ice, salt, and water in the tub. Explain the difference in the results obtained in Trials 3 and 4.
Tabulate and report all the data which you have recorded.
EXERCISE IV REPORT
CLASSIFICATION OF ICE CREAM
In the absence of the adoption of any uniform standard classification of ice cream, the following classification in use by the authors is given. It is simple, yet comprehensive, and is arranged according to fundamental differences in composition. This seems to be the most logical basis for classifying ice cream and is very satisfactory from a laboratory standpoint. Exercises and representative formulas will be given for each of these classes.
I. Plain or uncooked ice cream, often known as Philadelphia ice cream, is made from cream, sugar, and flavoring, with or without condensed milk or some stabilizer. It may be subdivided as follows:
1. Plain—Flavors such as Vanilla, Chocolate, Caramel, Coffee, Mint, etc.
2. Fruit—Flavored with fresh or canned fruits such as Peach, Pineapple, Strawberry, Cherry, etc.
3. Nut—Flavored with such nuts as Walnut, Almond, Filbert, Chestnut, Pistachio, etc.
4. Bisque—Flavored with Marshmallows, Macaroons, Sponge Cake, Nabisco Wafers, Grape-nuts, etc.
II. Cooked ice cream, often known as French or Neapolitan ice cream, is made from cream, sugar, flavoring, and eggs. As custards they sometimes contain flour or cornstarch. The following subdivisions are recognized:
1. Parfaits or French—Flavors such as Vanilla, Chocolate, etc., are most common, but various fruits are sometimes used.
2. Puddings—These are highly flavored with various dried and candied fruits, nuts, and spices. Examples are Nesselrode, Roman, and English Plum.
3. Custards—These contain flour, cornstarch, tapioca, or other similar ingredients, and are almost always flavored with vanilla.
III. Sherbets and Ices are made from water or milk, sugar, often egg albumen and a stabilizer, and flavored with fruit juices or other natural flavoring. The most prominent classes are the following:
1. Ices—Made from water, sugar and some natural flavoring without eggs or a stabilizer. This may include granites and frappés. Granites are frozen with little agitation, while frappés are only semi-frozen to a slushy consistency.
2. Water Sherbets—are made the same as ices with the addition of egg whites and sometimes a stabilizer. If the whole egg is used, they are sometimes called souffles.
3. Punches—are ices or water sherbets flavored with liquors or highly flavored with fruit juices and spices.
4. Milk Sherbets—Made from skimmed or whole milk, sugar, and egg whites, with or without a stabilizer and flavored with some natural flavoring.
5. Lacto—Made from skimmed or whole sour milk instead of sweet milk but in other respects they resemble milk sherbets.
IV. Mousse is a rich cream, sweetened and whipped to a stiff froth, flavored and frozen in moulds or cans.
In the laboratories at the New York state agricultural college 20% cream is used in making all plain or uncooked ice creams. Therefore in the following exercises and formulas a 20% cream is used as a base in most cases. This, however, may be reduced to 18% or 16% if it is thought desirable.
It must be remembered that the formulas given are for laboratory use and are not especially recommended as ideal formulas for commercial use. Many of them have given good results in commercial plants but there are so many variations and combinations possible that no single formula or group of formulas can be given as ideal for all commercial plants.
If the use of condensed milk is desired eight pounds of whole condensed milk may be substituted for the same amount of cream with excellent results in any of the formulas given for plain ice cream. Most commercial plants use condensed milk to give the ice cream more body and better standing quality.
THE USE OF STABILIZERS
A stabilizer of some kind is generally admitted to be necessary in commercial ice cream. The three most commonly used are gelatin, ice cream powders and gum tragacanth.
Gelatin may be prepared in any of the three following ways, using either milk or water for dissolving it. However, if milk is used, one of the first two methods should be used, so as to avoid any cooked flavor from boiled milk.
1. Using one pint to one quart of water or milk to each two ounces of gelatin, soak the gelatin in the cold liquid for fifteen to thirty minutes. Then heat the mixture up to a temperature of 160 degrees to 170 degrees F. and add to the cream with rapid agitation.
2. The same as number one, except heat the mixture only to a temperature of 125 degrees to 130 degrees F. for a sufficient time to thoroughly dissolve all of the gelatin.
3. Heat the necessary amount of water to boiling, dump the gelatin into it and stir till dissolved. Then add to the cream with rapid stirring.
Ice cream powders should be used according to the directions given with them.
Gum tragacanth stock is made in the following manner. Place the dry gum in cold water, using one ounce of gum to four pounds of water. Heat slowly and uniformly over a low flame or better in a double boiler to a temperature of about 110 degrees F. Hold at this temperature for several hours or until the dry gum has absorbed all the water it will hold. It does not go into true solution in water but will absorb about fifty times its own weight of the water. Strain through a coarse strainer and cool. It is then ready for immediate use. Sometimes enough is made at one time to last for several days, in which case it is best to add sufficient sugar to keep it from spoiling.