Pucker Up: Sweet and Sour Science

Sweet science: Sugar is not the only substance that can add sweetness. Hold a lemonade taste test and discover the properties of other sweeteners.

Key concepts:ChemistrySugar

Introduction

Background

Materials

• Six medium- to large-size lemons (Alternatively, you can buy pure lemon juice at the store.)
• Pure cane sugar (table sugar)
• Water: two and one quarter cups
• Artificial sweetener (Splenda or Sweet'n Low)
• Three spoons
• One knife
• Three drinking cups
• Strainer
• Bowl
• Permanent marker
• Liquid volume measurer (at least one cup volume)                                          
• One-quarter teaspoon measuring spoon
• Volunteer taste testers (optional)
• Additional cups (three for each volunteer) or large spoons (three for each volunteer)

Preparation

• To make the lemon juice, slice lemons into four pieces (across the length of the lemon works best) then squeeze the juice into the volume-measuring cup. Squeeze lemons until you have one cup lemon juice.
• Strain the lemon juice into another plastic cup, and then pour the strained juice back into the liquid volume-measuring cup.

Procedure

• Using the liquid volume–measuring cup, pour one-quarter cup of lemon juice into three different cups.
• Use the liquid volume–measuring cup to add three-quarter cup of water to each cup. Stir the contents of the cups with a spoon to mix the juice with water.
• Now it's time to add the sweeteners!
• To the first cup add no sugar or artificial sweetener.
• To the second cup add one-quarter teaspoon of pure cane sugar (table sugar). Stir with a spoon until the sugar is entirely dissolved, with none left on the bottom.
• To the third cup add one-quarter teaspoon of artificial sweetener (Splenda or Sweet'n Low). Stir until the sweetener is entirely dissolved, with none left on the bottom.
• Now it's time for the taste testing! If you have volunteers, you can pour each taste tester a small sample into other cups—or have each person take a large spoonful to taste. Take a small sip of unsweetened lemonade.
• Take a small sip from the lemonade sweetened with sugar.
• Now take a small sip of the lemonade sweetened with artificial sweetener.
• Extra: Can you make lemonade sweetened by sugar and artificial sweetener equal in sweetness? Start with the one that is bitterer and add more of its sweetening substance, in one-quarter teaspoon increments, until it tastes just as sweet as the other lemonade.

Observation and Results

Did you find that the lemonade made with artificial sweetener was sweeter than that made with sugar? Did the original sugar lemonade taste almost as sour and bitter as the pure lemon juice?

Artificial sweeteners are synthetic compounds designed to produce the intense sweet taste you observed in the artificially sweetened lemonade. In fact, the sweetness of artificial sweeteners is many times that of sugar. This means that if you add equal quantities of sugar and an artificial sweetener, the drink with the artificial sweetener will taste sweeter.

If you completed the "Extra" challenge, you may have seen that it took several teaspoons of sugar to equal the sweetness of the artificial sweetener. Splenda is 600 times sweeter than sugar and saccharine, found in Sweet'n Low, is 300 to 500 times sweeter. In the lemonade some of the sweetness is masked by the sourness of the lemon so you will not need to add 100 more teaspoons of sugar to get the same sweetness as one-quarter teaspoon of sweetener.

Although artificial sweetener does not add additional calories to foods and drinks that use it, we don't know exactly how it works inside our bodies after we consume it, so scientists are still looking into health effects.

More to ExploreComparing the Sweetness of Sugar and Sugar Substitutes, from Science BuddiesSensory Science: Testing Taste Thresholds, from Artificial Sweeteners May Evict Good Gut Microbes, from Society for Science & the PublicYeast Reproduction in Sugar Substitutes, from Science Buddies

Science Buddies

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