From HEMI WEINGARTEN
If you rely on American supermarkets for your sustenance, then no doubt you have bought and eaten products sweetened with corn syrup. Just look at the ingredient list of bread, cookies, candies, sauces, snack bars, and more to see how prevalent an ingredient corn syrup is.
While sugar, most high fructose corn syrup (aka HFCS – not the same as corn syrup!), agave nectar and other nutritive sweeteners count as 100% “sugars” in the nutrition facts panel, corn syrup elegantly gets away with a limited contribution to the total sugar count in a product.
A serving of sugar is 1 teaspoon. It has 4 grams of Total Carbohydrate, per the nutrition facts label below. All 4 grams of carbs (100% of carbs) are from Sugars.
This, however, is not the case with corn syrup. Below you can see the label for Karo Corn Syrup. A serving is 2 tablespoons, and it contains 30 grams Total Carbohydrate. As a sweetener, you would expect those 30 grams to be coming from Sugars. Alas, only 10 grams, or 33% are Sugars. Where are the other 20 grams?
Here’s a “real world” product example:
Walmart’s butter-flavored syrup pictured above lists corn syrup and HFCS as its two main ingredients. The rest are flavorings and preservatives that don’t add calories or carbs.
The Total Carbohydrate count, 53 grams, is therefore the sum of carbs from the corn syrup and HFCS. But the total Sugars count is only 29 grams, when one would expect it to be 53 grams as well (check any real maple syrup for comparison).
Knowing that Sugars are only one third of the Total Carbohydrate count in corn syrup we can deduce that there are 36 grams of corn syrup used here, and 17 grams of HFCS.
(Mathematically we solved 2 equations for 2 variables:
- x + y = 53
- 0.33x + y = 29
x= corn syrup grams, y = HFCS grams)
Again, the question is – why would corn syrup carb grams be three times as high as their sugar grams? What are those other carbs?
To try and answer the question, we sent a sample of Karo corn syrup to Anresco laboratories for a Sugars Analysis. The results came back within a couple of weeks:
Approximately 13% is dextrose, also known as glucose. This is the simplest form of sugar, a single molecule (monosaccharide), most readily absorbed by our bodies and used for quick energy. Another 12% is maltose, a slightly more complex sugar made from 2 glucose molecules bound together. Maltose is a type of disaccharide. (Another famous disaccharide is sucrose, more commonly known as table sugar. Sucrose is composed of one molecule of glucose and onle molecule of fructose)
We also know that corn syrup is about 25% water (see this USDA data chart). So together with the dextrose and maltose, we have accounted for 50% of corn syrup’s composition.
But what about the other half? Obviously they are carbs. If they were Sugars, then they would need to be labeled as such on the Karo product and in all foods where corn syrup is used. Right?
Corn syrup, as its name implies, is derived from corn. Your average corn kernel has a very high starch content (about 80% by weight). And starch is simply a long chain of sugar molecules bound together. Imagine a pearl necklace. Each individual pearl is a glucose molecule. All those glucose molecules are strung together by chemical bonds that create the so called pearl necklace, or in technical terms, a glucose polymer.
Making a sweet corn syrup out of a starch is simply a matter of finding the “scissors” to cut the necklace into smaller pieces, some pieces as small as just one pearl. The single pearl, or basic sugar molecule, is called glucose.
Fructose is another example of a single sugar molecule. All single molecule sugars are called monosaccharides.
Double molecule sugars such as sucrose (table sugar) are called disaccharides. Lactose, a disaccharide found in milk made of glucose + galactose. (Now you know why plain yogurts and milks are labeled as containing sugars, even when they don’t really taste sweet.)
More definitions: Oligosaccharides are chains of 3 up to 10 monosaccharides. Polysaccharides are defined as monosaccharide chains that are even longer. An example of these long chain saccharides is maltodextrin ,which can be 3 to 17 glucose units long. Oligosaccharides and polysaccharides are sometimes called higher sugars.
Corn starch can be broken down using various enzymes and acids. It becomes a mixture of monosaccharides, disaccharides, oligosaccharides, and polysaccharides. The exact proportion of each glucose polymer determines various properties such as sweetness, viscosity, solubility, fermentation capability, etc.
There is an almost endless number of saccharide combinations that can be derived from corn starch, with each tailored to the required end result. Corn syrup is mostly longer chain saccharides, with about one sixth free glucose and one sixth maltose (a disaccharide).
Now, here’s how the FDA defines Sugars for the purpose of nutrition labeling:
the sum of all free mono- and disaccharides (such as glucose, fructose, lactose, and sucrose)
…a serving of corn syrup has 30 grams of Total Carbohydrate, but only 10 grams of Sugars. Now we know that the other 20 grams of carbs are longer chain saccharides and thus technically don’t qualify for the FDA term “sugars”.
A few notes:
From a taste perspective, corn syrup is not as sweet as table sugar – only about 40% of the sweetness. The longer the glucose chain, the less sweet. But even pure glucose is only 62% as sweet as table sugar. Table sugar is sweet because of the fructose molecule joined to the glucose.
From a digestion perspective, our body absorbs all 30 grams of corn syrup pretty much in the same way. Everything quickly gets converted (broken down) into glucose (monosaccharide) and drives blood glucose up.
From a nutrition label perspective- If the fiber count of a product is zero, it makes sense to look at the Total Carbohydrate count instead of just the Sugars count, because the product may contain many grams of “higher sugars” that metabolize just as fast as the simpler sugars included under “Sugars” .
This post was prepared with the help Carol Harvey, Director of food/nutrition labeling and product development at Palate Works.
1. Harvard School of Public Health
2. John S. White, Ph.D., President, White Technical Research
3. FDA website and 21 C.F.R. 101.9