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What is corn syrup, and how should you use it? Your questions, answered.

Corn syrup will keep indefinitely opened or unopened at room temperature.  (Scott Suchman/For the Washington Post)
Corn syrup will keep indefinitely opened or unopened at room temperature. (Scott Suchman/For the Washington Post)
By Becky Krystal For the Washington Post

Corn syrup manages the unlikely feat of being one of the most valuable and most misunderstood ingredients in the kitchen. It can do a lot that regular granulated sugar can’t, plus improve both the appearance and texture of baked goods and confections.

Here’s what you need to know about this baking staple.

Q: What is corn syrup?

A: Corn syrup is a liquid sweetener. It is made primarily of glucose, a simple sugar “and the most common sugar from which living cells directly extract chemical energy,” says Harold McGee in “On Food and Cooking.” Based on a method first developed in the mid-19th century, corn syrup is formed when starch molecules from corn are treated with acid or enzymes, which today typically come from molds, McGee says. This process breaks down the starch into glucose chains of various lengths, forming a syrup. Shorter glucose fragments lend corn syrup sweetness and longer ones its characteristic viscous texture. (In Europe, the starch of choice is more often wheat or potato, and the resulting product is called glucose or glucose syrup.) The syrup is “then clarified, decolorized, and evaporated to the desired concentration,” McGee says.

Corn syrup is typically sold in light and dark versions. Light corn syrup is flavored with salt and vanilla, while molasses and caramel flavor and color are added to dark, says Lauren Chattman in “The Baking Answer Book.”

It will keep indefinitely opened or unopened at room temperature, according to “The New Food Lover’s Companion” by Sharon Tyler Herbst and Ron Herbst. You can also refrigerate it, but the syrup will thicken over time.

Q: Is it the same as high-fructose corn syrup?

A: No. High-fructose corn syrup is corn syrup that has been further treated with enzymes to break down some of the glucose into another common sugar, fructose. Fructose “is the sweetest of the common sugars,” McGee says, which makes high-fructose sweeter than regular corn syrup. Unlike corn syrup, high-fructose corn syrup is not sold on the shelves to home cooks.

In “BraveTart: Iconic American Desserts,” Stella Parks laments the fact that corn syrup “gets a bad rap because of its evil twin.” The insidious issue with high-fructose corn syrup, which is about as sweet as table sugar but cheaper, is that it is often used in processed foods “where you’d least expect it,” Parks says, contributing to the consumption of more added sugars than people may realize.

Q: How does corn syrup compare to table sugar?

A: Corn syrup is 30% to 50% as sweet as table, or granulated, sugar, McGee says. (High-fructose is 80 to 90%.) I’m often contacted by readers tripped up by its inclusion in a recipe, so it’s important to keep in mind that as with any other type of sugar in a recipe, corn syrup is doing more than just providing sweet flavor. And when it does lend sweetness, it will be less cloying than a similar amount of granulated sugar.

Q: Why should I use corn syrup?

A: Like butter, cream of tartar or citric acid, corn syrup is an “interfering agent” that helps prevent crystallization, Rose Levy Beranbaum says in “The Baking Bible.”

This ability is especially valuable in candy-making, McGee says, because the long, tangly glucose strands slow down the movement of sugar and water molecules and keep sucrose crystals from binding to each other, which would otherwise lead to a grainy, solidified texture. That’s why you’ll often find recipes for caramel or other confections (such as marshmallows) that call for corn syrup. Similarly, corn syrup helps make ice creams and sorbets smooth and creamy, because it interferes with the formation of ice crystals much as it does with sugar. My go-to ice cream recipes from Jeni Britton Bauer, of Jeni’s Splendid Ice Creams, use corn syrup.

As little as a tablespoon of corn syrup can lend glossy sheen to a chocolate ganache, as well as buttercream or other icings, Shirley Corriher writes in “BakeWise: The Hows and Whys of Successful Baking.” Corriher also cites the wisdom of Monroe Boston Strause, an early 20th-century pie maker and innovator who employed corn syrup in crumb crusts to keep them easy to cut. In “CookWise: The Secrets of Cooking Revealed,” Corriher says that a tablespoon added to a batch of cookie dough can enhance browning and encourage a crisp exterior.

The glucose in corn syrup binds water well, helping prevent moisture loss and extending the shelf life of baked goods “without the cloying sweetness” of honey or other sugar syrups, McGee says.

Corn syrup is acidic, McGee explains, so when it reacts with baking soda, the resulting carbon dioxide can contribute to the rise of baked goods when it inflates the air pockets already in a dough or batter.

Q: What can I substitute for corn syrup?

A: As with many baking recipes, you will get the most consistent results by using the ingredients tested by the developer. Because of its specific makeup and function, corn syrup can be hard to replace without having unintended consequences, but there are a few options that can get the job done in a pinch.

The best swap would be the nearly identical glucose syrup. Granted, it’s not readily available on grocery store shelves, at least in the United States.

Cook’s Illustrated did tests with recipes for chocolate frosting and glazed chicken to evaluate brown rice syrup as a corn syrup substitute. Brown rice syrup has roughly the same level of sweetness as corn syrup (about half as sweet as sugar), though it skews thicker and has a “pronounced cereal aroma,” the magazine says. That being said, brown rice syrup performed similarly in the two recipes, though that may not be the case where there aren’t as many other flavors to mask its stronger presence. Moreover, brown rice syrup is more expensive per ounce than corn syrup.

Beranbaum notes that you can use Lyle’s Golden Syrup interchangeably with corn syrup. Keep in mind that golden syrup is thicker and sweeter than corn syrup. For minimal amounts, you may be able to get away with honey. Otherwise, it’s not an ideal substitute, as honey is about 25 to 50% sweeter than sugar, while corn syrup is much less so.

Light and dark corn syrup can be substituted for one another, Chattman says, as long as you take into account the richer color and more molasses flavor of dark corn syrup.

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