This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
Fat. The flavor of the ice cream is influenced by the ingredients that go into it. They should be free of foreign odors and flavors. Ambrose states that "increase in butter fat gives the richness of flavor that can be obtained in no other way."
Williams and Campbell conducted experiments in ice-cream making in which the fat content was varied: creams were made with 12, 15, and 18 per cent fat, the other constituents remaining the same, and the method of making being kept uniform in each experiment. Purchasers were allowed to sample the three ice creams on the first day and on the following day could purchase their choice. The records showed that 80 per cent of the purchasers favored the ice cream containing 18 per cent fat, 10.4 per cent favored the ice cream containing 15 per cent fat, and 7.6 per cent of the purchasers favored the ice cream containing 12 per cent fat.
Salt. Salt may be added to ice cream, and for some persons the flavor is thereby improved. It is so easy to add too much that it is often better to omit it. A good proportion to use is about 1/2 teaspoon of salt per gallon of mixture.
Acidity. Acidity of the cream affects the flavor. The acidity of milk and cream increases with age. An acidity of 0.30 per cent produces an apparent sour taste; that usually preferred for ice cream is from 0.16 to 0.20 per cent.
Sugar. Williams and Campbell in experiments with ice cream, conducted like those just referred to with the fat, but in which the percentage of sugar varied, found that 61.4, 28.4, and 10.2 per cent of the purchasers showed a preference for the 19, 16, and 13 per cent sugar, respectively. This gives a total of 90 per cent favoring the ice cream with 16 or more per cent of sugar.
Serum solids not fat. Similar experiments with serum solids not fat showed that 55.6, 25, and 18.6 per cent of the purchasers favored the ice cream containing 12, 9, and 6 per cent of serum solids, respectively.
In regard to gelatin, 63.2, 13.8, and 23 per cent of the purchasers favored the ice cream containing 1, 0.5, and 0 per cent of gelatin, respectively.
Fisher states that the serum solids do not affect the flavor until a content of 12 per cent and beyond is reached. To obtain this amount of serum solids, condensed-milk or dry-milk products must be used. With 12 per cent or greater a condensed-milk flavor is imparted to the ice cream. Fisher also states that butter fat improves the flavor slowly.
Sandy ice cream. When too great an amount of condensed milk is added, there is danger of the lactose crystallizing at the low temperatures in the holding room. When the lactose crystallizes, a sandy or gritty texture is imparted to the ice cream. Such ice cream is called sandy. Leighton and Peter have reported that lactose does not usually give sandiness to the ice cream unless the concentration of serum solids is high, i.e., about 12 per cent or more. The lactose may crystallize in the ice cream when the percentage of lactose is 6 per cent or more.
Flavoring. Flavoring is added to the ice cream. Too little flavoring to blend with the cream and sugar gives a flat taste; too much makes the flavoring the only ingredient evident to the taste. Dahle states that "Nothing is to be gained by the use of cheap flavors." Crushed fruit, fruit juices, and nuts are also used to flavor ice cream.