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Have you ever questioned how candy is made?
We know that the candies available in the market come in various shapes and textures: chewy like fudge, fluffy like marshmallows and cotton candy, tough like lollipops, and crunchy like stone candies and rock sweets. The technique to create these one-of-a-kind treats comply with a comparable chemical process.
What is candy made of?
The main ingredient to make most candies is sugar. Sugar is a general term to describe a class of molecules that includes carbohydrates such as glucose, sucrose, and fructose.
Intermolecular forces are indispensable in dictating the state of sugar, as they mediate as well as control the attraction among sucrose molecules. When sugar is mixed with water, a partial number of sucrose molecules break apart from one another. Here the sugar molecules are attracted to water molecules via intermolecular forces and the hydrogen bonds formed by the attraction between polar components.
How are candies made?
To make most sorts of candies, we usually start by dissolving sugar in boiling water. This forms a syrup, which we let cool down after taking it off the burner. Although it sounds simple, how we cool the syrup can make all the difference.
For instance, in the formation of rock candy, we let the syrup slowly cool down over many days until big sugar crystals form. However, in the formation of fudge, we continuously stir the syrup after an initial cooling period. This ensures that when the sugar crystals form, they stay small and stay in limited quantities. In the same way, sugar is spun to form sugar and glass candy in which we have to rapidly cool the syrup quickly to stay crystals from forming
The main difference between these different types of candies is whether sugar crystals form and if so, what size is the sugar crystals
There are two categories of candies that can be made from the crystallization process:
- Crystalline – candies which contain crystals in their finished form.
- Non-Crystalline – candies which do not contain crystals in their finished form.
So how do sugar crystals form, and what causes them to possess different sizes when the syrup is cooled down?
Each grain of sugar consists of small crystals made from an orderly arrangement of molecules called sucrose, which is a carbohydrate. Sugar is a disaccharide composed of glucose and fructose.
Fig: Formation of the sucrose molecule
Source: https://socratic.org/questions/explain-why-lactose-shows-mutarotation-but-sucrose-does-not
The sucrose molecules are arranged in a repeating pattern in a sugar crystal that extends across three dimensions. All of these sucrose molecules are attracted to one another by intermolecular forces. Intermolecular attractions are a sort of interaction that binds several molecules together and is comparatively weaker than the bonds between atoms in a molecule.
When sugar is added to water, a number of the sucrose molecules start separating from each other because they’re attracted to the water molecules, as shown in the image below.
Fig: Interaction between sucrose molecules and water molecules
Similar to the intermolecular forces present between sucrose molecules, water and sucrose also interact through intermolecular forces.
The dissolving process involves two steps. Firstly, the water molecules bind to sucrose molecules. Secondly, the water molecules pull the sucrose molecules away from the crystal and into the solution.
Generally, only a certain amount of solid particles can be dissolved in water at a given volume and temperature.No more of that solid will dissolve in water if we add more than the required amount. We say that the solution is saturated at this stage, and the extra solid simply falls to the bottom of the container.
Fig: Interaction between sucrose molecules and water molecules
As we continue adding more granulated sugar to the solution, the rate of dissolving decreases while the rate of crystallization increases. This continues till both rates acquire equilibrium in which the number of sucrose molecules leaving the crystals is the same as the number of sucrose molecules joining the crystals. This means that the sugar solution is now saturated. Similarly, molecules in supersaturated liquids will crystallize much quicker and easier as they are highly unstable in nature.
As a result, beyond that factor, if we add more sugar crystals, the process of dissolving will carry on, however, it’ll be accurately balanced by using the technique of recrystallization. Accordingly, the sugar crystals can no longer dissolve in water and the crystals and the solution are in equilibrium. This denotes that the size of the crystals stays the same, even though the sucrose molecules are continuously trading places among the solution and the crystals.
Some candies that we can make through the crystallization process include: Rock candy, Geode Candy, Fudge, Kendal Mint Cake
Some candies require no crystallization to take place. There are a few methods we apply to prevent crystallization from happening. Crystallization interfering agents can include adding more glucose, using brown sugar instead of white since brown sugar is more acidic, add fat, or add acids like vinegar or bicarbonate of soda or cream of tartar.
Some candies that require prevention of crystal formation include: Lollipops, Caramels, Toffee, Marshmallows.
To prevent crystal formation, you cool the sugar syrup so rapidly that no crystals have time to form. The dissolved molecules of sucrose tend to bind to each other randomly. When this happens, the candy is a noncrystalline solid.
Generally, the heating temperature of non-crystalline candies is higher than that of crystalline candies because they usually consist of a higher concentration of sucrose. As soon as non-crystalline candies have been cooked and cooled, they need to be ‘ripened’. This procedure includes storing the sweet to allow the moisture stage to rise slightly and redissolve any small crystals which have formed in the sugar solution which results in smooth candies.
Fig: Candy Stretching
Source:https://stcatharinesmuseumblog.com/2016/11/04/ask-alicia/
Once we have the syrup in place one can also let it cool into a “sugar dough” and stretch it according to the type of product we desire. This dough can be moulded into various shapes and designs that remain intact until consumed. This technique can be used to make rolled lollipops, design/image candies, peppermint canes, and anything else that one’s heart desires.
In conclusion, it’s the careful handling of the crystallization of sucrose that allows us to create such enormous varieties of candies. Who knew such simple, little candies might be so complicated?
Citations
Cover photo: https://www.rd.com/list/most-popular-candy-the-year-you-were-born/
- Media, C. (n.d.). candy science. Steam. https://www.steampoweredfamily.com/candy-science/
- Media, C. (n.d.). Chemistry Behind Candy Science. Steam. https://www.steampoweredfamily.com/candy-science/#:~:text=The%20Chemistry%20Behind%20Candy%20Science&text=The%20Sucrose%20molecule%20is%20a,sometimes%20a%20bit%20of%20fat. https://www.exploratorium.edu/cooking/candy/sugar.html
- T.B.C.C.A, c. (2015, October 24). Sugar Chemistry. Understanding Ingredients for the Canadian Baker. https://opentextbc.ca/ingredients/chapter/sugar-chemistry/#:~:text=Chemically%2C%20sugar%20consists%20of%20carbon,Monosaccharides%20or%20simple%20sugars
- Young, L. B. (2020, November 11). The chemistry behind sugar. reagent. https://www.reagent.co.uk/chemistry-behind-sugar/
