How do they measure the sweetness of sugar substitutes?

Answers to your questions about the news.
May 14 2007 7:12 PM

How Sweet It Is?

Measuring the intensity of sugar substitutes.

Illustration by Mark Alan Stamaty. Click image to expand.

The companies behind artificial sweeteners Splenda and Equal settled a lawsuit on May 11 over the veracity of Splenda's advertising slogan, "Made from sugar so it tastes like sugar." Nevertheless, there are some real differences between the two products: Splenda is 600 times sweeter than sugar, while Equal is only 200 times sweeter. How do scientists measure sweetness?

With taste panels. Researchers present each trained participant with samples of water that have been artificially sweetened to varying degrees. First, the tasters are given plain water, and then, they drink samples with higher and higher concentrations until they start to taste something different—not necessarily sweet, just different. When half the test population can detect a change in the water, flavor chemists know they've reached what's called the "threshold value" for the compound. Scientists can measure relative sweetness by comparing the threshold values for various types of sugar and sugar substitutes.

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Sucrose, or table sugar, is the taste that every artificial sweetener tries to mimic. Everyone has different sensitivities, but scientists estimate that the general population can detect a solution of about 0.5 percent sucrose—that's one teaspoon of table sugar dissolved into several cups of water. By comparison, one-six-hundredth of a teaspoon of sucralose, the sweetener in Splenda, would make the same impression on your taste buds. But don't be too impressed just yet; sucralose is still a lightweight compared with neotame, which is 7,000 to 13,000 times sweeter than table sugar. (From taste panel tests we also know that fructose—one of the sweeteners in nondiet soda—is 1.4 times sweeter than sucrose; glucose, a monosaccharide found in honey and vegetables and also added to soda, is about three-quarters as sweet; and lactose, a kind of sugar found in milk, is one-half as sweet.) * Ready for a DIY test? It's a bit like wine tasting—don't forget to rinse between samples.

Even putting aside the differences in sweetness, it's easy to spot the taste of Equal, Splenda, and Sweet'N Low. That's because our taste buds pick up more than just how sweet something is. We can also detect how the sweet taste comes and goes, and what it feels like in our mouths. We experience the sweetness at its maximum level about 4.1 seconds after it hits our tongues. This burst of sugary flavor diminishes over the course of about a minute. Saccharin, the compound in Sweet'N Low, hits the taste buds a little faster, but when the sweetness subsides, it can leave behind a bitter aftertaste. Equal's ingredient, aspartame (or Nutrasweet), sometimes gives a metallic aftertaste, though less so than saccharin. Luo han, a sweetener derived from a Chinese fruit of the same name, has a hint of licorice after the initial sweetness. Sucrose also has its own "mouth feel" that is distinct from those of the artificial additives.

Some scientists believe that the taste we recognize as sweet contains tiny traces of saltiness, sourness, or bitterness. They surmise that one reason artificial sweeteners taste "off" is because they don't strike the right balance of these other flavors.

Got a question about today's news? Ask the Explainer.

Explainer thanks Veronica McBurnie, Lyn Nabors of Calorie Control Council, Devin Peterson of Pennsylvania State University, and Robert Shallenberger of Cornell University.

Correction, May 15, 2007: This article originally implied that fructose is the only sweetener in nondiet soda. High-fructose corn syrup contains fructose, glucose, and other sugars. (Return to the corrected sentence.)

Michelle Tsai is a Beijing-based writer working on a book about Chinatowns on six continents. She blogs at ChinatownStories.com.