Objective

Students will learn how to make hard candy

Background

Hard candy is a type of glass made from sugar. In this lab we are using table sugar and corn syrup. Recall that table sugar is sucrose. All sucrose molecules have the same shape so they are able to stack pretty well together just like building blocks or Lego blocks. This is bad for hard candy texture since this will result in recrystallization of the sugar. Therefore to overcome this, two different types of sugars are added to get between the sucrose sugar blocks. This is where corn syrup comes. Corn syrup is made up of glucose and fructose. If you don’t have corn syrup, adding lemon juice can cause the splitting of some of the sucrose molecules into glucose and fructose which also produce this effect. Have fun making candy!  

Materials

  1. White table sugar
  2. Corn syrup
  3. Food flavoring
  4. Food coloring
  5. Lemon juice
  6. Measuring cup 
  7. Table spoon
  8. Candy thermometer (optional)
  9. Stove 
  10. Mixing spoon
  11. Baking sheet

Method 

WARNING: HIGH TEMPERATURE! BEWARE OF BURNING. WEARING A MITTEN AND LONG-SLEEVE SHIRT WILL HELP. YOU MAY ALSO CONSIDER WEARING AN APRON. 

  1. Measure and add the following to a cooking pot: 3 cups granulated sugar, 1 cup corn syrup, 1 table spoon lemon juice, 1 cup water
  2. Heat on stove to dissolve while mixing continuously to prevent the bottom of the pot from burning 
  3. Continue heating and mixing until the temperature reaches 300 degrees Fahrenheit. Note: A thermometer that can reach 300 degrees Fahrenheit will provide the best accuracy but if you don’t have a thermometer, you can check for doneness by periodically dropping some of the syrup in a transparent glass of cold water. Watch as the syrup falls. If it forms a thread, it is not yet ready (this is the thread stage). Continue cooking until the syrup makes a large firm ball/lump when it falls in the water. This is called the hard-crack stage. See the image below.  
  4. At the end of cooking, turn off the stove and add a drop or two of food coloring and food flavoring and mix to combine thoroughly
  5. Pour the molten candy on a baking sheet and allow to cool to room temperature (a fan will speed up the process)
  6. Break and collect in Ziploc bags
  7. Taste and enjoy your handy work 

Hard Crack Stage

Watch this great video from Wired that explains how candy is made on a larger scale. Note though that the principles are the same.

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Courtney Simons
Courtney Simons
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Dr. Simons is a food science educator. He earned his bachelor’s degree in food science, and Ph.D. in cereal science at North Dakota State University.