Editor’s Note: This is Part II of Ben Marcus’ series on the science of sugar. For Part I, click here.
When was the last time you saw a processed food in the grocery store with real sugar in it? Odds are, its’ been a while. Over the past few decades, most food manufacturers have decided to forgo sugar for corn syrup to save costs.
Corn syrup is by far the most common sugar substitute you’ll find in processed foods. Manufacturers use this sweet substance in mass quantities to sweeten everything from soft drinks to canned foods to candy. It definitely has a different taste than real sugar – have you tried Coca Cola Life, Pepsi True, or Berghoff or Goose Island Root Beer, which are all made with real sugar? If you compare a drink sweetened with corn syrup and one sweetened with cane sugar, you will notice right away that the one with the real sugar is much sweeter. In fact, sucrose (table sugar) is 2-4 times as sweet as corn syrup.
Why is corn syrup less sweet than table sugar? Well, our tongues find the sugar molecules in table sugar sweeter than the sugar molecules in corn syrup. Table sugar is made of two-part sugar chains composed of one glucose molecule and one fructose molecule, while corn syrup is made of pure glucose. Fructose is sweeter than glucose, and as a result, table sugar is sweeter than corn syrup
Further, corn sugars don’t start sweet. They naturally come in long, branched molecules called starches, which aren’t sweet at all. In fact, bread, pasta, and cereal are mostly made of starches, and they’re not sweet unless you douse them with table sugar! This is because your tongue cannot “see” individual glucose molecules when they’re locked up in long starches. So for them, its like there’s no sugar there – hence, no sweet treat for your brain. To make cornstarch sweet, manufacturers have to break down these long chains into smaller pieces that your tongue can actually sense.
To make corn syrup, chemists apply acid to cornstarch, which breaks it down into smaller chains of 3-5 glucose molecules. These chains still aren’t that sweet, but after a bit more time sitting in acid, they break down even further into single glucose molecules. Finally, something your taste buds can recognize!
Manufacturers can control how thick and sweet the syrup will end up by controlling how much the starch molecules break down: the more small chains that are left behind, the thicker and less sweet the syrup will be.
What do food manufacturers do when they want a sweetener as cheap as corn syrup but as sweet as sucrose? They convert corn syrup into the sweetener that everyone loves to hate: high-fructose corn syrup (HFCS). To synthesize HFCS, chemists convert glucose into fructose by subjecting corn syrup to a complicated chemical process. Since fructose is sweeter than glucose, HFCS is sweeter than regular corn syrup. Until recently, HFCS was the sweetener of choice in most prepared foods because of its price and sweetness. But despite this advantage, HFCS has been assumed to cause obesity and heart disease (primarily because the obesity epidemic in the US spread at the same time has the use of HFCS). However, just because two things happen at the same time doesn’t mean that one caused the other, and it turns out there is no clear evidence that HFCS is more unhealthy than table sugar. Nutritionists recommend that if you need something sweet, use non-caloric artificial sweeteners like Splenda (learn more here).
If you have more questions about sugar and whether or not it’s healthy, check out this FAQ from the American Heart Association.