Chemistry of Sour Candy
Hopewell Valley Student Podcasting Network
Chemistry Connections
The Chemistry of Sour Candy
Episode #5
Welcome to Chemistry Connections, my name is Anna Zhao and I am your host for episode #5 called The Chemistry of Sour Candy. Today I will be discussing the chemistry behind turning regular sugar into hard candy and the chemistry behind citric acid.
Segment 1: Introduction to Candy
Hard candy is a product made predominantly from sugar and corn syrup that may be flavored or colored, and is characterized by a hard, brittle texture.
When we talk about candy making, one of the central ideas is crystallization. This is the process where sugar molecules arrange themselves into a well defined, repeating structure known as a crystal. The texture of the candy whether its smooth like caramel or crunchy like rock candy, depends on how the sugar crystals are formed.
Segment 2: The Chemistry Behind Sour Candy
At the heart of candy making is a simple ingredient we all know: sugar, or more specifically, sucrose. Now, lets zoom in and further look at the polarity of sucrose. Sucrose is a polar molecule, meaning it has distinct positive and negative ends.
The overal polarity depends on both the individual bond polarities, and the geometry of the molecule.
Electronegativity is the ability of an atom to attract shared electrons in a covalent bond. When two atoms in a molecule have different electronegativities, the electrons in the bond are not shared equally, resulting in a polar bond. The atoms in sucrose are Carbon with an electronegativity of 2.55, Hydrogen with an electronegativity of 2.20, and oxygen with an electrogetivity of 3.44.
Using these values, it is determined that C-H bonds have an electronegativity difference of 0.35 (smal diff), C-O have 0.89 (large diff considered polar), and O-H have a diff of 1.24 (very large diff considered very polar).
C-O bonds are polar because oxygen is more electronegative than carbon. This causes a partial neg charge on the oxygen atoms and a partial pos charge on the carbon atom. O-H bonds are even more polar due to the larger electronegativity difference between oxygen and H. This results in a partial negative charge on the oxygen atom and a partial pos charge on the hydrogen atom.
Sucrose is a three dimensional structure with hydroxyl (OH) groups extending in various directions. The asymmetry of the molecule means that the dipole moments of the bonds do not cancel each other out, making the molecule polar.
Knowing that sucrose is polar is important because it explains how and why sugar dissolves in water.
So what happens when you heat it up? When you heat a sugar and water solution. You’re not just dissolving sugar. You’re actually changing the crystal structure. By applying heat, we separate the highly bound sucrose crystals, allowing us to manipulate them in new ways. Basically, raising the temperature of the sugar solution increases the amount of sugar that can dissolve in water, creating what’s known as a supersaturated solution. As the solution cools, the sugar will start to recrystallize into a solid mass.
Terms like “softball” and “hardcrack” are often used by candy makers to describe the texture of the sugar solution when it’s heated to specific temperatures. For instance, at around 235°F to 245°F, you get what is known as the softball stage which is perfect for making softer candies like fudges and fondants. Heating it up to 300°F to 310°F is known as the hard crack stage which is needed for making hard candies like lollipops. The higher the temperature is, the harder the candy becomes because you’re reducing the water content.
As the sugar solution cools, the sugar molecules start to recrystallize. If you’re making, for example, rock candy, you should leave the mixture undisturbed to allow the sugar molecules to come together slowly and form large crystals. On the other hand, if you want a smoother texture or consistency, you need to agitate the mixture to prevent the formation of large crystals.
There are multiple ways to achieve this. Stirring is one way, while another way is adding invert sugars like corn syrup. Invert sugar is a mixture of glucose and fructose, which interfere with sucrose crystalization. These molecules combine with the sucrose in a way that disrupts the formation of the large crystals.
Another way is to add acids like lemon juice or cream of tartar to the candy mixture which convert some of the sucrose into invert sugar, achieving the same result.
As you can see, acids play a huge role in candy making. So we’re now going to shift focus onto citric acid how it is used to add sourness to sweet candy. Citric acid is a natural acid found in citrus fruits like lemons, limes, and oranges and is what gives their characteristic flavor.
Sourness is the taste our tongue detects from acidity. Specifically, it is the hydrogen ions H+ that are responsible for the taste.
When citric acid comes in contact with water (Like in our saliva), it dissociates. This means the citric acid molecule (C6H8O7) releases hydrogen ions. The hydrogen ions combine with water molecules to form hydronium ions h3o+. Our tongues have receptors for H3O+ and once they detect it, they send signals to our brain telling us we are tasting something sour.
So every time you eat sour candy, it’s essentially a mini chemistry experiment happening in your mouth!
Segment 3: Personal Connections
The main reason I chose this topic is that I love eating candy just like billions of people around the world. I’ve also grown up making candy at home , where I used to make tanghulu with my grandma which is like a chinese snack thats basically a fruit skewer dipped and coated in hardened sugar/candy, I’ve found that not only is candy making a fun activity, It’s a great way to learn about chemistry in a delicious, and tangible way. I’ve always been curious about the chemical properties and processes involved, especially how such simple ingredients can be transformed into such a wide variety of textures and flavors. I hope you enjoyed this topic and I hope that next time you enjoy a sweet treat, this makes you think more about the chemistry it took to make it, and the chemistry happening in your mouth!
Thank you for listening to this episode of Chemistry Connections. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.
Sources:
List your sources here. Make sure they are linked. Wikipedia cannot count for more than 50% of your sources.
https://www.youtube.com/watch?v=6MoBvV12C58&ab_channel=WIRED
https://en.wikipedia.org/wiki/Citric_acid
https://www.youtube.com/watch?v=KXs_axKuPvE&ab_channel=RandyMakesCandy
Music Credits
Warm Nights by @LakeyInspired
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