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Ask Paul: What’s So Great About Corn Syrup?

Why not just use sugar?
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Published Mar. 2, 2022.

Mac asked: Is corn syrup just sugar from corn?

To turn corn into a sweetener, manufacturers start with the starch of the corn. 

Starch is a polymer: a molecule made up of many identical sub-molecules linked together. Each individual unit making up a starch molecule is a glucose molecule, a simple sugar. When the glucoses are  all strung together, the polymer is too big to fit into our sweet taste receptors, but if glucose units are separated from the starch, they taste sweet.

Using acid or enzymes that snip the bonds between the glucose units, manufacturers convert each chainlike starch molecule into many smaller lengths. Similar conversions take place in our bodies when we digest starch; when fruits ripen; and when beer is brewed. 

To make standard supermarket corn syrup, starch is broken down into short chains of various lengths, as follows. Fifteen percent or so is glucose; another fifteen is maltose (which consists of two glucose molecules and is less sweet) and the majority is chains such as maltotriose, which are made up of three or more glucose units, and are not very sweet at all. Those larger chains give corn syrup its viscosity, which makes it a great addition to baked goods, ice cream, candy, and other recipes: It adds chewiness, slows down the formation of unwanted ice and sugar crystals, and gives appealing body to frozen treats and beverages.

Supermarket corn syrup typically comes in light and dark versions, which differ in flavor: Light corn syrup is flavored with vanilla, and dark corn syrup has a mild molasses taste from the addition of cane-sugar-refining byproducts.

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Supermarket corn syrup tastes less than half as sweet as an equal weight of white sugar—so it’s not sweet enough to be the main sweetener in sweet foods. But an additional enzymatic treatment step can be used to convert some of the glucose in the syrup to fructose, another naturally occurring simple sugar that tastes sweeter than glucose. The inclusion of fructose makes a syrup known as high-fructose corn syrup that has the same sweetness level as white sugar. Because it’s cheaper and easier to work with than white sugar, high-fructose corn syrup is extremely popular in food manufacturing.

There are plenty of other sweetening syrups in the kitchen—honey, cane syrup, maple syrup, molasses, to name a few—but none of them have those longer chains, so they don’t have the magical viscosity of corn syrup. Simple syrup, which is just white sugar dissolved in water to make it easier to use, adds nothing but sweetness to a cocktail (much more sweetness than corn syrup would). Cocktail nerds have been known to add a tiny bit of powdered gum acacia to simple syrup, to make gum (or “gomme”) syrup: The gum’s viscosity gives a pleasing smooth body to drinks.

Ask Paul Adams, senior science research editor, about culinary ambiguities, terms of art, and useful distinctions: paul@americastestkitchen.com

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