Oh yes my friends, we hear all about the evils of corn syrup (sometimes called glucose syrup) from the food police, especially the sinister demon-brew known as “high fructose corn syrup” (ominously initialized HFCS). Corn syrup is the packaged food industry’s most pervasive sweetner, found in everything from Coke to ketchup. And of course anything that’s that broadly used simply must be evil. An articifially created, chemically modified, fatally addictive hyper-sugar, a team effort by the National Corn Growers Association, Columbian drug lords, Dow Chemical, Pepsico, Karl Rove and Satan.
Given that perception, most people are surprised to learn that corn syrup is actually a natural product, one you can buy at any Whole Foods. It’s made of course from corn. Specifically, the starch of common “dent” or “field” corn.
But how do you get from a corn kernel to a drop of corn syrup? As I mentioned a week or so ago in answer to a question about Karo syrup, the process starts by steeping corn kernels in water to loosen their husks and hydrate their starch. Once the kernels are soft the water is drained off and they’re ground into a kind of wet paste or slurry. Next, the whole soup is passed through a series of filters and centrifuges that separate out the husks and germ to yield the pure starch.
Lastly, enzymes (which as you may recall from previous posts are non-living organic molecules that living things use to execute various jobs in their bodies) are let loose in the slurry to start breaking those big starches (elaborate sugar molecules) down. Isolated from bacteria cultures, the enzymes snip the long-chain sugars into their component parts: single-sugar glucose molecules, which unlike the long-chain sugar molecules they came from, taste sweet to our tongues.
Originally, corn syrup manufacturers only had a few types of enzymes at their disposal to execute the dismantling (hydrolysis) process (the very earliest used acids). And once they started the hydrolytic process, they had no way of stopping it. Thus early corn syrups were composed almost entirely of glucose. Great, right? Except that it turns out that the simplicity of a given sugar molecule doesn’t necessarily correspond to the sensation of sweetness in human beings. Thus while glucose is the simplest of all sugars, a syrup made entirely from it only tastes about 70% as sweet as table sugar (exactly why that is is a subject of intense debate among biologists). So while early corn syrups did make a suitable replacement for molasses in things like pecan pie, they still weren’t sweet enough to replace actual table sugar (sucrose).
All that changed in the 1960’s when a new enzyme called glucose isomerase was isolated, again from bacteria. This enzyme was capable of converting elementary glucose into a slightly more complicated molecule, fructose. The advantage there being that fructose tastes 20% sweeter to our tongues than sucrose (table sugar). By blending that fructose with their pure glucose, corn syrup makers finally had a way to make a syrup whose sweetness was on par with table sugar.
In time, other techniques were developed to stop and start various types of enzymatic activities, allowing manufacturers to finely tune their product with a mix of different sugars. Today, your typical corn syrup is made of something like 53% glucose and 42% fructose. High-fructose corn syrups are up to 75% fructose. The important thing to remember here is that while the sensation of sweetness may vary from one sugar to another, they’re all the same in terms of the number of calories they deliver. So while a syrup high in fructose may taste sweeter than sugar, from a fat-creating standpoint, it’s no worse than any other sugar. Which to my mind is what makes the whole demonization of high fructose corn syrup so darn silly. But more on that later.