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Food52's Test Kitchen Manager Erin McDowell is here, with tips and tricks to help you master the ABCs of baking.
Today: What's the deal with corn syrup? You may be surprised.
This may be the first time I’m going to type a phrase that I know will stir the masses into a fiery hubbub of contention (turns out when you make a living writing about cake and cookies, there’s not a lot of debate surrounding your offerings). But I will not hide behind a sticky plastic bottle as I make this proclamation. It’s true: Corn syrup isn’t evil, at least not entirely—and definitely not for the reasons you think it is.
I’ll admit that I began the journey to this opinion completely uninformed. In pastry school, we used corn syrup, especially when we were making candy, ice cream, certain frostings and glazes, and pastries. We also used other sweetener syrups. They weren’t used interchangeably: Everything was used in certain amounts and ratios, but aside from what was asked on our standard end-of-week tests, I didn’t really care to know why.
But when I left school and started writing recipes for home cooks, the questions/comments/angry rants started pouring into my inbox. “Corn syrup?!? Ugh!” People demanded substitutions for this vile, processed product that, in their minds, was responsible for the fattening of our entire country and the downfall of our culinary contributions to the world.
I was enraged, too; having read The Omnivore’s Dilemma and The End of Food, I set out to figure out what we could be using at home to replace this awful ingredient. What I discovered instead was lot of information that, while not strictly in defense of corn syrup (or the plethora of processed foods it can be found in), proved I’d been looking at it all wrong. But before I start sounding like one of those “It’s made from real corn and it’s fine in moderation” commercials, let’s looks at some facts.
The first step to understanding corn syrup is to understand sugar. There are dozens of varieties of naturally occurring sugars, but for the purpose of this discussion, we’ll be focusing on four: sucrose, glucose, maltose, and fructose (these specifics come from Harold McGee’s book On Food and Cooking).
Sucrose is the scientific name for our regular, commonplace granulated sugar. Plants naturally produce sucrose during photosynthesis, and it’s most commonly harvested from the stalks of sugar cane and the stems of sugar beets. It is composed of 2 molecular parts: 1 glucose molecule and 1 fructose molecule. Compared to the other sweeteners we’ll be discussing, it is the second in concentration of sweetness (and, unlike fructose and glucose, tastes good when used alone in larger amounts). It is the second most soluble sweetener and will dissolve in a 2:1 solution of sweetener to water to produce a naturally thick solution (think simple syrup). Sucrose melts at 320° F and caramelizes at 340° F.
Glucose, also known as dextrose, is a naturally occurring sweetener that can be found in fruit and honey. Glucose is only a part of a composition that contains many molecules, with the glucose molecules building chains of starch in more complex structures. Glucose is less sweet than sucrose, less soluble in water, and produces a thinner sugar solution. It melts and begins to caramelize at 300° F.
Maltose is the formation of 2 glucose chains together. Its sweetness level, solubility, and melting/caramelization temperatures match those of glucose.
- Fructose, also known as levulose, has the same molecular composition as glucose but the atoms are arranged differently, which results in different structural chains. Like glucose, fructose is naturally occurring and can be found (along with other sweeteners) in fruit and honey. Fructose is the sweetest of the four and the most water-soluble (4 parts fructose will dissolve in 1 part water); it also absorbs and retains water more effectively than the other fruit sweeteners. It melts and caramelizes at just 220° F. Additionally, fructose possesses several unique properties. The structure of the molecule actually changes when dissolved in different temperatures of water, and these structural changes affect its discernible level of sweetness. Fructose seems sweeter when dissolved in cold water, with a sweetness closer to that of sucrose when dissolved in warm water. Most interestingly, our bodies metabolize fructose more slowly than sucrose or glucose. This slow metabolization raises blood glucose levels more slowly, making it the lowest naturally occurring sugar on the glycemic index (and therefore preferable to other sugars for diabetics).
The Syrup Discussion
Armed with this information, it’s now easier to understand our next segment: the syrup discussion. The first ingredient to understand is called glucose syrup (which is sometimes shortened in recipes and formulas to "glucose"—for purposes of clarification, I’ll refer to by its longer form). Glucose syrup was first made in Russia, where they discovered that adding an acid to potato starch broke down the starch (inside which glucose exists) and resulted in a thick sugar syrup. Over time, scientists found that using malted barley instead of an acid produced similar results. Eventually, in countries that produced high volumes of wheat, this technique was used to break down wheat starch rather than potato starch. Regardless of the original plant origin (in America, it's generally wheat) the resulting sweetener is called glucose syrup.
Glucose syrup isn’t commonly available in grocery stores, but it is used widely in professional kitchens, bakeshops, and commercial food production. As someone who has used it, I can say that it’s wonderful and useful for a variety of reasons (and now I even understand why). Glucose syrup essentially consists of long strands of carbohydrates that get all tangled together but never fully bond. This creates a thick syrup that’s thicker than even the most concentrated sucrose solution.
When you add glucose syrup to a recipe, it continues to get tangled with the other ingredients in the formula; it interferes with the molecules and how they move and bind to one another. This prevents (or at least drastically reduces) the other sugars present in the recipe from forming the crystals that create a grainy, unpleasant texture. It also helps reduce the formation of ice crystals in frozen desserts, which leads to smoother, creamier results. Additionally, glucose syrup contains some acid and thereby contributes to leavening by reacting with baking soda or other chemical leaveners. It also makes baked goods chewier and more tender and helps retain moisture, which prolongs shelf life.
Corn syrup is produced from corn (no surprise) and is produced in essentially the same way as glucose syrup. First, the starch is extracted from the corn. Then an acid is added to break down the starch into individual glucose molecules and short glucose chains (maltose). The mixture is finally clarified and evaporated to create a thick syrup.
First revelation: Corn syrup is essentially glucose. Yes, it is processed in a way that alters glucose from its naturally occurring form (in nature, glucose is usually present alongside other sugars, not alone), but it is basically just glucose. Plus, it’s the closest product to glucose syrup you’ll find in a standard grocery store (though the wonders of the internet mean you can have access to glucose syrup if you prefer it).
But most importantly, the advantages of using corn syrup are the same as those that come from using glucose syrup: prevention of crystallization (both from sugar and ice), better internal textures, leavening assistance, moisture retention, and a longer shelf life.
Some types of corn syrup are treated with additional enzymes that convert some of the glucose into fructose. This creates a sweeter syrup—known as high fructose corn syrup—that can be used in smaller amounts to achieve the same level of sweetness. It's very appealing to large companies producing processed food and drink: Because they need less of it to sweeten a product, they save money. High fructose corn syrup usually contains about 53% glucose and 42% fructose. By controlling the digestion of starch, additional varieties of corn syrup can be made, including maltodextrin and high maltose corn syrup. All three of these syrups are used in commercial production of hundreds of processed foods but are not readily available for consumer purchase.
While the exact consequences of consuming large amounts of fructose are still being studied, it should be noted that corn syrup as its sold in regular stores generally is not of the high fructose variety (and Karo brand syrup contains no high fructose corn syrup). Just like all refined sugar, corn syrup shouldn't be consumed in excessive amounts, but using it in baking recipes doesn't necessarily need to be avoided beyond the normal concerns of eating too much sugar.
One additional syrup of note is invert sugar. Invert sugar is made by heating sucrose with an acid. Much like the acid breaks down the starch in the production of glucose syrup or corn syrup, acid also breaks down sucrose into its two sub-parts (glucose and fructose). This process, called inversion, results in a thick syrup that’s about 75% glucose and fructose and 25% sucrose. Due to high levels of glucose and fructose, invert sugar also prevents crystallization and is used just as commonly as glucose syrup in professional kitchens, bakeshops, and commercial food production. Invert sugar is available for purchase online, but you can even make your own by adding citric acid to a sucrose solution. It should be noted that invert sugar syrup is discernibly sweeter than corn syrup and is therefore most often used in conjunction with sucrose in recipes (basically just enough so that it can aid to the prevention of crystallization).
So what’s the takeaway? Certainly not that all sweeteners are created equal. I’m just as outraged as the next person by the high level of sweeteners (especially processed sweeteners) in processed foods and I’m certainly not suggesting that anyone make consumption of these products a part of your diet by saying that corn syrup is a-okay.
But when it comes to baking at home, these sweeteners have a purpose. Understanding why corn syrup gives you perfectly smooth caramels or creamy gelato is something we should all take into account when trying a recipe that calls for it in ingredient list.
When do you use corn syrup? Share with us in the comments below.