By Mary F. Henry
Success in sugar cookery, as in all other cookery, requires intelligent work and to work intelligently means that one must understand the nature of the materials used, the changes that occur during the process of cooking, and the conditions that bring about desirable, and prevent undesirable, changes. The behavior of sugar under different conditions largely determines the quality of the product.
While there are many different kinds of sugar, those of interest to the housekeeper are of two classes: in the one group are the familiar granulated cane or beet sugar, maple sugar, and brown sugar; in the other is glucose, commonly known in the form of a clear, sticky sirup. Corn sirup consists of a mixture of glucose with dextrines and other substances. Molasses contains large amounts of cane sugar. These two classes of sugar differ greatly in characteristics. Sugars belonging to the first class are very sweet and crystallize in large crystals, with which all are familiar; glucose is less sweet, and either crystallizes less easily in much finer crystals or remains as a heavy sirup of creamy consistency. In certain kinds of candy, this creamy texture is one of the requisites. The fact that in the process of cooking it is possible to change a part of the crystalline sugar into glucose with its finer texture is one of the chief factors in making candy. The whole problem of preventing the formation of the undesirable granules, or crystals, is simply to convert some of the crystalline sugar to glucose and to avoid conditions that may cause candy to grain.
* Keeping Christmas. Cornell Reading-Course for the Farm Home, Bull. 97.
While the simple boiling of sugar brings about to some extent this desired change of crystalline sugar to glucose, the addition of a little acid, such as cream-of-tartar, greatly hastens the process. It is possible to get the same result by substituting glucose for a part of the sugar in the first place.
Overcooking, that is, cooking beyond the correct temperature, causes graining, for glucose contains more water than does crystalline sugar, and overcooking drives off the water and forces the glucose to go back to sugar.
A crystal of sugar falling into the solution may cause the whole mass to crystallize. Hence care must be taken not to allow crystals to be carried up to the side of the pan and fall back into the mixture. Washing down these crystals carefully with a swab prevents trouble from this source.
Stirring the mixture while it is cooking may cause crystallization, especially in the case of fondant, which contains only sugar and water. When milk is used, it is necessary to stir the mixture occasionally to prevent its sticking to the pan. There is not the danger, however, of graining in this case, for milk and cream both tend to prevent crystallization. Stirring the mixture while it is hot or cooling it too suddenly may cause crystallization.
Another problem is one that concerns the length of time for cooking sugar mixtures. It is well known that when sugar is heated with water a sirup is formed. If the heating process is continued, water is driven off as steam, and the sirup becomes thicker, or more concentrated. As the concentration increases, the temperature rises.
The stage of concentration to which the solution is to be boiled depends on the kind of product that is to be made. The terms thread, soft ball, hard ball, crack, hard crack, and caramel are used to distinguish the different stages. While the ordinary method used by amateurs for testing candy consists in dropping a little of the solution into cold water, more uniform and accurate results may be obtained by the use of a thermometer. A glass thermometer may be bought at a drug store for about $1.25. In using a thermometer, care should be taken that the bulb is entirely covered by the sirup and that it does not reach the bottom of the kettle; if the bulb is exposed to the air or touches the metal of the pan, the registered temperature is lower in the one case and higher in the other than is the actual temperature of the sirup.
In the absence of a thermometer, however, the test already mentioned, dropping a little of the boiling sirup into cold water, may be used with comparatively good results. The following table gives the different stages of concentration, the corresponding temperatures, and the tests that may be used to determine the condition of the sirup. The temperatures refer to a sirup made from cane sugar. When glucose or corn sirup is used in part, the same consistencies are reached at lower temperatures.
230° F. 110° C.
Sirup forms a thread when dropped from a spoon
236° F. 113° C.
Sirup forms a soft ball when dropped into cold water
Hard ball . . ..
252° F. 122° C.
Sirup forms a hard ball when dropped into cold water
270° F. 132° C.
Sirup becomes brittle when dropped into cold water
293° F. 145° C.
Sirup becomes very brittle when dropped into cold water
310°+ F. 154°+ C.
Sirup changes color and becomes very hard and brittle when cool
Wooden spoons are preferable to metal ones, for wood does not conduct heat as does metal. Moreover, the sirup does not tend to stick to wood as much as to metal.