Corn syrup doesn’t have a single chemical formula because it’s a mixture, not a pure compound. Its primary sugar is glucose (C₆H₁₂O₆), but the syrup also contains maltose, maltotriose, and longer sugar chains, all dissolved in water. The exact proportions of these sugars vary depending on how the syrup is manufactured.
Why There’s No Single Formula
A chemical formula describes one specific molecule. Table salt is NaCl. Water is H₂O. Corn syrup, however, is a concentrated solution of several different sugars produced by breaking down corn starch. Because it contains multiple compounds in varying ratios, no single formula can represent it. If you need to assign one formula for a class assignment, C₆H₁₂O₆ (glucose) is the best approximation, since glucose is the dominant sugar in most corn syrups.
The Sugars Inside Corn Syrup
Corn starch is a long polymer of glucose molecules linked together. During manufacturing, enzymes called alpha-amylases chop those links apart, producing a range of sugars depending on how long the process runs. The result is always a mixture of four categories of sugar:
- Glucose (dextrose): C₆H₁₂O₆, a single sugar molecule. In a heavily processed corn syrup (95 DE, explained below), glucose makes up about 93% of the sugar content.
- Maltose: C₁₂H₂₂O₁₁, two glucose molecules linked together. A mid-range corn syrup may contain around 35% maltose.
- Maltotriose: C₁₈H₃₂O₁₆, three glucose molecules linked together.
- Higher saccharides: Longer chains of four or more glucose units. In a lightly processed corn syrup, these can account for nearly 70% of the sugar content.
All of these sugars are built from the same building block, glucose, just in chains of different lengths. The liquid itself also contains about 24 to 30% water by weight. Federal standards require corn syrup to be at least 70% total solids.
How Dextrose Equivalent Changes the Mix
The sugar profile of corn syrup depends on a measurement called dextrose equivalent, or DE. This number tells you how far the starch has been broken down. Pure starch has a DE of zero. Pure glucose has a DE of 100. The higher the DE, the more the starch has been chopped into small, simple sugars.
The food industry commonly uses four grades. A low-conversion syrup (around 29 DE) is only 9% glucose but 69% longer sugar chains. A standard grocery store corn syrup sits around 42 to 49 DE, with roughly 20% glucose, 31% maltose, and the rest split between maltotriose and higher sugars. A high-conversion syrup (around 95 DE) is almost entirely glucose at 93%, with only traces of anything else.
This is why “the” chemical formula for corn syrup is a trick question. A bottle labeled “corn syrup” could contain wildly different proportions of sugars depending on its DE grade. The light corn syrup in your pantry is a very different chemical mixture from the high-glucose syrup used in industrial food production, even though both start from the same starch.
How It Differs From High-Fructose Corn Syrup
Regular corn syrup contains essentially no fructose. Every sugar in it is glucose or a chain of glucose molecules. High-fructose corn syrup (HFCS) starts as regular corn syrup but goes through an additional step where enzymes convert some of the glucose into fructose (C₆H₁₂O₆, same formula as glucose but with a different molecular structure). The two most common versions are HFCS 42, which is 42% fructose, and HFCS 55, which is 55% fructose. The remainder is glucose and water. HFCS 55 is the version used in most soft drinks, while HFCS 42 is more common in processed foods and baked goods.
So while glucose and fructose share the molecular formula C₆H₁₂O₆, their atoms are arranged differently, which gives them different levels of sweetness and different behavior in the body. Regular corn syrup is less sweet than table sugar precisely because it lacks fructose.
Why the Mixture Matters in Cooking
The fact that corn syrup is a mixture rather than a pure sugar is exactly what makes it useful. When you make candy, dissolved table sugar (sucrose) tends to form crystals as it cools, producing a grainy texture. Corn syrup’s blend of different-sized sugar molecules physically gets in the way of crystal formation. The maltose, maltotriose, and longer chains act as obstacles, preventing glucose molecules from lining up into an orderly crystal lattice. This is why recipes for caramel, pecan pie, and marshmallows call for corn syrup: it keeps the final product smooth.
The viscosity of corn syrup also comes from this mixture. Longer sugar chains make the syrup thicker and stickier, which is why low-DE syrups (with more long chains) are noticeably more viscous than high-DE syrups (which are thinner and sweeter).