Corn Syrup’s Secret Labeling Trick Explained [Part 2 / 2]

Karo Corn Syrup Nutrition

This post was prepared with the help Carol Harvey, Director of food/nutrition labeling and product development at Palate Works.

Yesterday we showed how corn syrup can be used in a product to lower the nutrition label sugar count. Today, we explain the reason behind this. Don’t worry, we’ll try to keep the geek speak to a minimum.

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)

If you recall from yesterday, 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” .

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

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  • Tom Z

    TY for this article. But now I’m confused about what you stated under “digestion perspective”, i.e., “higher sugars” metabolize just as fast. What then makes for some sugars, e.g. Agave having a lower glycemic index?

    • carol

      Fructose — more complicated/slower to metabolize than glucose (or multi-glucose chains)

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