What is corn syrup and why is it used to make hard candy?

Corn syrup is a moderately sweet invert sugar derived from corn. The type of corn syrup purchased from the grocery store is not the same as High Fructose Corn Syrup.  High Fructose Corn Syrup (HFCS) is made by further processing regular corn syrup into fructose and glucose, making the resultant syrup extra sweet.  Large-scale manufacturers use HFCS as an inexpensive alternative to sugar.  Some corn syrup brands might add HFCS as an ingredient in their formulation, but most major brands, including Karo® Syrup, have removed it.   Manufacturers are obligated to list HFCS on their labels if it is used, so check the ingredient list on the product label.  

Corn syrup is a common ingredient in many hard candy recipes because it is an invert sugar.  Invert sugar inhibits the formation of sugar crystals and provides a smooth texture to hard candy, caramel, and other cooked sweets. Corn syrup can also be used to add moisture and shine to dessert sauces and frosting, extend the shelf-life of baked goods, and prevent ice crystals from forming in ice cream and other frozen desserts. 

Corn syrup is readily available in the U.S.  Look for it in the baking aisle or pancake mix and syrup aisle of your grocery store.  Corn syrup is often available in Light and Dark and refers to the color of the syrup.  For candy making, light corn syrup should be used.  Dark corn syrup contains molasses and has a deep brown color and much more robust flavor.  Reduced calorie, or “Lite” corn syrup is also not recommended for candy making.

Glucose (another invert sugar) is used by professionals and can be substituted at a 1:1 ratio.  Many professional cake and candy supply stores will sell glucose.

Another option is to use Hi-Sweet, which is a powdered corn syrup.  Making candy using Hi-Sweet will help keep hard candy from getting sticky in humid weather. Hi-Sweet is available on our website.

An invert sugar can be made by adding an acid such as citric acid or cream of tartar to a simple sugar syrup and boiling it.  Here are two recipes:

How To Make Cane Syrup (The Kitchn)  

Invert Sugar Recipe (Pastry Chef Eddy Van Damme)