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Technique Theory: Standard Wet-Sugar Cooking
Appears in
By Peter Greweling and Culinary Institute of America
Published 2007
Knowing the simple procedures of the standard wet-sugar cooking method—and having an understanding of the basic theory behind each of those procedures—is invaluable to the confectioner and will help him or her succeed consistently in sugar confectionery. Two simple goals are at the heart of sugar cooking: the sugar must first be dissolved, and then the desired amount of water must be removed. Each of the following steps helps to prevent recrystallization of the sugar.
- IN A POT OR CANDY KETTLE, COMBINE SUGAR WITH 20 PERCENT OR MORE WATER TO MAKE THE SUGAR THE TEXTURE OF WET SAND. The water in this procedure is the solvent: it is the substance into which the sugar dissolves. Without the water, the sugar could not go from a crystalline state to an amorphous, or noncrystalline, state. The precise amount of water used is not critical, provided it is sufficient to dissolve the sugar fully. Twenty percent is a satisfactory amount. At the boiling point, sugar solutions can dissolve approxim-ately 80 percent sugar. So, when the 20 percent solution is heated to boiling, it is certain that all of the sugar will dissolve. Using more water will not generally be harmful to the finished product, but, since the goal of sugar cooking is to remove the desired amount of water, the cooking time will be increased by using a greater percentage of water. (See Sugar Cooking.)
- PLACE THE POT ON THE HIGHEST POSSIBLE HEAT WITHOUT THE FLAME COMING UP THE SIDES. Sugar should always be cooked on the highest possible heat. There are two primary reasons for this: to minimize unwanted browning and to prevent crystallization. Sugar cooked to a high temperature, as when making hard candy, browns more when it is cooked slowly than when it is cooked quickly. The browning not only affects the candy’s color but also brings with it caramel flavor notes that are often not welcome. The more quickly the sugar reaches the terminal temperature, the less browning occurs. Cooking a sugar solution rapidly helps to prevent crystallization by putting more energy into the system, making the sugar solution less likely to revert to a crystalline state. These two factors are the reasons why, in confectionery shops, syrups are cooked in copper kettles on powerful candy stoves. The copper conducts heat extremely well, and the rounded bottom of the kettle provides a large surface area for heating, resulting in a fast cook. The stoves in confectionery shops are fitted to accept the kettles for the most efficient transfer of heat into the syrup.
- STIR CONSTANTLY WITH A WOODEN SPOON UNTIL THE SOLUTION COMES TO A BOIL. Stirring a syrup as it comes to a boil helps to ensure that the sugar crystals circulate throughout the syrup, dissolving quickly and completely. Any undissolved sugar crystals remaining in the solution act as seeds, or nuclei, forming more sugar crystals, which themselves then initiate further crystallization. Confectioners traditionally use wooden paddles or spoons for stirring, as metal conducts heat away from the solution, resulting in cool spots in the syrup that are more prone to crystallization.
- WHEN THE SOLUTION REACHES A BOIL, STOP STIRRING. Stirring—as beneficial as it is to the syrup during heating—becomes detrimental once the solution begins to boil. Stirring, or any other agitation, of a supersaturated solution can initiate crystallization by causing the sugar molecules to collide and bond together to form crystals. (See sugar crystallization diagrams.) The exception to this rule applies when the solution contains a dairy product or another type of ingredient that will burn if not stirred during cooking. In formulas containing such ingredients, allowances are made for this excess agitation in the form of extra doctoring agents.
- REMOVE IMPURITIES FROM THE TOP OF THE SOLUTION. When syrup first reaches a boil, gray foam often coalesces on the surface of the sugar. This foam can be caused by traces of mineral salts left in the sugar from the refining process or by any other impurities that may be present in the syrup. These impurities should be removed in order to improve the appearance of the finished product and to prevent the impurities from becoming seeds on which sugar crystals can form. The quantity of impurities in the sugar depends on the refining and storage of that sugar and may range from being virtually nonexistent to covering the entire top of the syrup.
ADD A DOCTORING AGENT TO THE SOLUTION. In confectionery, doctoring agents—also called “doctors”—are ingredients added to help prevent or control the crystallization of sugar. Three categories of doctoring agents are typically used in candy making: glucose syrups, acids, and invert sugar. While all of them help to control crystallization, each has its own characteristic effects on the final product.
- GLUCOSE SYRUPS. Glucose syrup is ubiquitous as a doctoring agent throughout confectionery. Glucose syrups with different dextrose equivalents (DEs) affect the finished product slightly differently with regard to texture, flavor release, and hygroscopicity. When using glucose syrup as a doctoring agent, add it after the solution reaches a boil, as it is easier for the sugar to fully dissolve in the water without the presence of the syrup. Low-DE syrups contribute to a chewy texture and less sweetness. Higher-DE syrups result in a shorter texture and greater levels of sweetness. (See Characteristics of Glucose Syrups.)
- ORGANIC ACIDS. Tartaric acid, cream of tartar, lemon juice, and vinegar are also commonly used as doctoring agents in sugar cooking. These ingredients work by inverting a portion of the sugar in the syrup. (See Inversion.) In addition to preventing crystallization, inversion makes the finished product softer, sweeter, shorter textured, more hygroscopic, and more prone to browning. Inversion is an ongoing process; as long as the sugar and acid are together in a fluid state, inversion will continue, resulting in a softer, stickier, and potentially browner finished product. In most cases these are qualities to be avoided. This is the reason some candy formulas specify the temperature at which to add the acid used as a doctoring agent.
- INVERT SUGAR. Invert sugar may be added to syrups directly. By adding invert sugar directly, rather than relying on acids to invert a portion of the sugar, the confectioner can get more consistent results that are not affected by variables such as the output of the stove, the strength of acids, or the hardness and pH of water. Regardless of whether invert sugar is a discrete ingredient or is created by inversion during cooking, it has the same tendency to increase sweetness, provide rapid flavor release, increase hygroscopicity, and contribute to potential Maillard browning. (See Maillard Reaction.)
- USING A MOISTENED PASTRY BRUSH, WASH DOWN THE SIDES OF THE SUGAR POT TO REMOVE ANY SUGAR RESIDUE. Repeat this step as often as necessary to keep the sides of the pot clean, but do not clean more often than necessary. Brushing the sides of the sugar pot with a wet brush removes the sugar crystals that are likely to form there and returns them to the solution. If such crystals are allowed to remain undissolved on the sides of the pot, they are likely to make their way back into the mixture after cooking, seeding it and initiating crystallization. Unless these crystals become part of the solution, they quickly become part of the problem! Remember that the goal when cooking sugar is to remove water from the syrup. Therefore it is counterproductive to wash the sides of the pot excessively, as this simply introduces more water that must again be removed. Clean the side of the pot only when there is sugar present on it.
- INSERT A THERMOMETER INTO THE SOLUTION AND COOK TO THE DESIRED TEMPERATURE. Alternatively, use a refractometer or a finger test to measure the concentration of sugar in the solution. Various methods exist for determining the percentage of water and sugar present in a cooking solution. The most common method is to use a thermometer and to cook the syrup to a predetermined temperature. At standard atmospheric conditions, sugar cooked to a given temperature will always contain the same percentage of dissolved solids. The following graph indicates the relationship between the temperature to which the sugar is cooked and the resulting dissolved-solids content. The thermometer is the most accessible, reliable method for determining the sugar density of a cooking mixture. Another highly accurate method is the use of a refractometer. Available in a variety of ranges, a refractometer quickly and accurately measures the density of a syrup without the fluctuations due to atmospheric pressure, altitude, and relative humidity that are inherent with a thermometer. Another time-honored method is to test the mixture using a bowl of ice water and one’s fingers. (See Stages of Sugar Cooking.) The finger test, while adequate for some purposes, and having enjoyed many years of use by confectioners, is subjective and dependent on the experience and skill of the confectioner. More consistent, accurate results are obtained by using either a thermometer or refractometer.
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