This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
The "cold-water" test. In the "cold-water" test, one can tell, from the firmness or hardness of a portion of the sirup which has been dropped into cold water, whether the sirup has reached a concentration required for the type of candy desired. The degree of firmness in the cold-water test is designated by different descriptive terms, such as soft ball, medium ball, hard ball, and brittle. It should be remembered that there is no definite stage between a soft ball and a medium one, but as the concentration of the solution gradually increases, the firmness of the sirup tested in cold water increases. One factor that causes variations in this test is the fact that the colder the water in which the sirup is tested the firmer the tested portion. Another cause for variation is that the portion being tested is not always left long enough to become cooled.
Yet with long practise the cold-water test can be used with great precision to denote the stage of cookery of a sirup. It is the different interpretations of what constitutes a soft or medium ball that makes this test a more difficult one to use. The number of terms used by different persons to suggest the same stage of cookery is illustrated by the following. In looking over a large number of recipes for a candy contest, it was interesting to find that of 600 recipes nearly 200 had exactly the same proportion of sugar, corn sirup, water, and egg white. But the directions for making the cold-water test in these 200 recipes varied. Here are some of the terms used to describe the portion of sirup tested in the cold water: Soft ball, medium soft ball, medium firm ball, firm ball, hard ball, solid ball, real hard, very hard, hardens, threads, soft crack, cracks, crackles, cracks and hops, hairs, spins hairs, strings, snaps, breaks, and brittle.
Stages of cookery. In part the descriptions of stages of cookery of sugar sirups are from "Terminology Used in Food Preparation." A sucrose solution that has reached a concentration indicated by a temperature of 110° to 112°C. does not form a ball when a portion of the sirup is tested in ice water, but spins a two-inch thread when dropped from a fork or spoon.
At a temperature of 113° to 115°C. a soft ball is formed when a portion of the sirup is tested in ice water. This ball is easily molded in the water, but does not retain its shape at room temperature. Sirup cooked to this stage is used for fondant, fudge, and penuchi.
At a temperature of 118°C. a firmer ball is obtained. At 122°C. the ball is still harder and less readily molded in the water. At 122°C. the ball retains its shape at room temperature. Sirups for caramels are cooked to 118° to 122°C. Temperatures of 118° to 123°C. are used for sucrose sirups that are to be poured over beaten egg white.
The sirup at temperatures of 121° to 130°C. forms an increasingly harder ball, which holds its shape, yet is plastic, when a portion is dropped into ice water; it is used for popcorn balls, nougat, divinity, and some taffies. The sirup at temperatures of 132° to 143°, called the soft-crack stage, separates into threads which are hard but not brittle when dropped into ice water. It is used for butterscotch and taffies. Sirups cooked to 149° to 154°C, the hard-crack stage, separate into separate threads which are hard and brittle when dropped into cold water; used for brittles and glaces.
The length of the thread or hair that forms when a fork or spoon containing some of the sirup is lifted into the air may also be used to indicate the stage of cookery.
Effect upon stage of cookery of addition of corn sirup and other sugars to sucrose solutions. The addition of corn sirups and other sugars to sucrose solutions modifies the firmness of the portion tested at a definite temperature in cold water.
Commercial corn sirup is composed of dextrin, dextrose, maltose, water, and a small amount of ash. Frandsen, Rovner, and Luithly state that its composition is as follows:
Since the composition of corn sirups may vary slightly, this may result in different degrees of firmness when different corn sirups are used with sucrose solutions. The use of corn sirup with sucrose in taffy, brittles, or caramels, candies that do not require crystallization, produces a definite stage of hardness when determined by the cold-water test at a lower temperature than when sucrose is used alone. Dextrin is the ingredient of the corn sirup that brings about this result, for if dextrin is used alone with sucrose the temperature for a definite degree of hardness is still lower than when corn sirup is used. In some of the early references on sugar cookery the term glucose is used for corn sirup.
Table 11 shows the effect of different proportions of sugar upon the stage of hardness in sugar cookery. Miss Daniels has reported similar results in part.
Amt. of dextrin
Amt. of corn sirup
Amt. of sucrose
Amt. of dextrose
It can be seen from this table that the greater the proportion of corn sirup used the lower the temperature to which the sirup needs to be cooked for a definite stage of hardness.