Answer: Stir the syrup with a spoon or a spatula. Stirring prevents the sugar crystals that start to form from growing too big. Stirring causes the sucrose molecules to be pushed into one another, forming crystal seeds throughout the syrup. The resulting crystals will be smaller when more of the crystal seeds are present, because the sucrose molecules can join any of a larger number of crystal seeds. If you want to make fudge, first heat the syrup to a temperature above the boiling point of water o C , and then pour it into a pan to make the syrup cool down faster.
The reason the syrup needs to cool quickly is that sucrose molecules do not have time to form enough intermolecular interactions to grow into large crystals. By contrast, if the syrup were to cool slowly, the sucrose molecules would have time to arrange themselves in larger crystals. After the syrup cools down to 50 o C, you can start stirring or scraping it. It is important to let the fudge cool down to 50 o C because if you stir during this cooling phase, crystal seeds will probably form too soon and, as a result, they may crystallize out of the solution, and the texture of the fudge would be grainy.
The syrup actually becomes supersaturated, similar to what happened to the syrup used to make rock candy—the syrup contains more sucrose molecules than can stay dissolved.
As you stir the fudge, many crystals form at once, and the stirring helps the sucrose molecules bind to one another and start forming small crystals. The main goal is to keep stirring continuously, which generates a larger number of small crystals. As the temperature decreases further, the sucrose molecules spread among the many crystal seeds and bind to any one of them, keeping the size of the crystals small.
This creates the rich, melt-in-the mouth texture typical of fudge. Some candies have no crystals at all. Examples of such candies include glass candy, gummies, and cotton candy. Glass candy is so-named because of its noncrystalline structure. But glass has a more general meaning: It is a solid with an amorphous structure, which is an irregular structure, with no pattern.
By contrast, a crystal is a solid with a highly ordered structure. For example, Fig. Figure 5. Comparison of the chemical structures of a an amorphous solid made of silicon dioxide — glass — and b a crystal of silicon dioxide — quartz.
To make glass candy, you cool the sugar syrup so rapidly that no crystals have time to form. The dissolved sucrose molecules start binding with each other, but in no particular order.
When this happens, the candy is amorphous, and it is an example of a glass. Gummies and marshmallows are produced similarly. In the case of gummies, gelatin is added to the sugar syrup to give it a rubbery consistency. Marshmallows also contain gelatin, but air is whipped into the mixture to expand it into a foam—a mixture composed of gas bubbles dispersed in a liquid. Cotton candy is produced a little differently because the process does not start with sugar syrup.
First, granulated sugar is heated in a cotton candy machine until it melts and the intermolecular forces between the sucrose molecules are broken. Having liquefied the sugar, the cotton candy machine then sprays the liquid through tiny nozzles so that it forms fine filaments of liquid that solidify immediately. This quick cooling of the liquid into open air does not allow the sucrose molecules to form crystals, and threads of glass are created instead.
These glass threads are so fine that they melt in your mouth, which is the wonderful experience of eating cotton candy.
Most candies are made from syrup yet their texture can vary substantially. Two factors play a key role: the length of time for crystals to grow, and the way the syrup is handled while it cools down. In the case of rock candy, the syrup is left for several days, which provides plenty of time for the formation of large crystals. In the case of fudge, because the syrup is stirred continuously, a large number of small crystals is formed.
When making glass candy, gummies, or marshmallows, the syrup is cooled down so quickly that no crystals can form at all. Making candies is actually chemistry in action.
You manipulate the size of sugar crystals—even if you cannot see them—to produce an array of textures. This skill has been developed over hundreds of years, before the science of candy-making was understood. But even then, this art form tells us something interesting about chemistry: It is not only the combination of ingredients that defines a product but also the way they are mixed together.
McGee, H. Tom Husband is a science writer and chemistry teacher in London, United Kingdom. Consumption of added sugar has significantly increased over the past 50 years, and this rise in consumption coincides with the rise of obesity, type 2 diabetes, and heart disease. So, is added sugar harmful? Careers Launch and grow your career with career services and resources.
Vanilla is often added to chocolate candies or other chocolate recipes because it complements and accents the flavor of chocolate. At this point, you have dissolved the crystal structure of the sugar. The sugar crystals are dissolved at this point in the process. But a single seed crystal of sugar clinging to the side of the pan might fall in and encourage recrystallization.
Most fudge recipes contain either corn syrup which contains glucose instead of the sucrose of table sugar or cream of tartar which breaks sucrose into glucose and fructose.
The different sugars tend to interfere with each other's crystallization and minimize the chance that the candy will crystallize too soon. They must be used in moderation, however -- too much and the fudge will remain a thick syrup forever!
The final stage is stirring the syrup when it is lukewarm to promote crystallization all at once throughout the candy. Disturbing stirring a very supersaturated solution causes many crystals to form at once. Because they compete with each other for the dissolved sugar, none can grow very large. The result is the proper creamy texture of fudge and the change in appearance from shiny supercooled liquid to dull a mass of very tiny crystals.
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