Making sugar sweeter

Follow these instructions to learn about different types of sugars and the secret to making them sweeter.

• 17 July 2006 | Updated 14 October 2011

• What you need
• What to do
• What's happening

Most chemists will tell you that sugar is a molecule containing carbon, hydrogen and oxygen. To everyone else, sugar is a sweetener. This activity will show you how you can change the sweetness of sugar by changing its chemical structure.

The following activity uses the hydrolysis of sugar to make iced tea sweeter.

Warning: for this activity, you will need to boil water. Ask an adult to help.

What you need

To do this activity you will need:

• two cups of boiled water
• tea bags
• a tablespoon
• sugar.

What to do

1. Fill two cups with boiled water from a saucepan or kettle. Add a tea bag to each cup.
2. In one cup, add two tablespoons of sugar. After a few minutes, remove the tea bags. Once they have both cooled, add two tablespoons of sugar to the unsweetened cup of tea (be sure to label the cups, so you can tell which one is which).
3. Once the sugar has dissolved, taste each cup of iced tea. Did you notice that the tea you sweetened while it was hot, is sweeter?

What's happening

Your first thought might be that more sugar dissolves in hot water than in cold water. But on the other hand, you know that the sugar was dissolved in both cups, and that they both had the same amount of sugar added to them. So why is one sweeter than the other? The hot water inverts the sugar (sucrose) to become glucose and fructose, which makes sugar taste sweeter.

Sugars are compounds of carbon, hydrogen and oxygen. The simplest sugars are called monosaccharides. Two commonly known monosaccharides are fructose (commonly found in fruit) and glucose. Both of these sugars are chemically identical in their composition (C₆H₁₂O₆), but structurally, they are different.

The common form of sugar is sucrose, which is a disaccharide. This means that it is made of two monosaccharides. In the case of sucrose, it happens to be a glucose molecule attached to a fructose molecule. Therefore, sucrose has a slightly larger formula (C₁₂H₂₂O₁₁).

Sucrose is found in all plants and is formed as a result of photosynthesis. Plants use chlorophyll to convert sunlight into a stored chemical form of energy - sugar. Sugar cane and sugar beet have the highest concentrations of sucrose and are therefore harvested for their sweetness.

Converting sucrose into fructose and glucose is a chemical process known as hydrolysis. A hydrolysis reaction is where water is used to break down a compound. The converted sugar is also known as 'inverted sugar'.

By hydrolysing sucrose into glucose and fructose, the taste of sugar becomes sweeter and it browns more easily. In fact, inverted sugar (glucose and fructose), is about 20 per cent sweeter than the sucrose it was made from. Therefore, inverted sugar is used to make sweeter confectionery.

Because inverted sugar can hold more moisture than sucrose, it is used to keep cakes and bakery products moist and fresh. Inverted sugar is also less viscous and softer in texture, making it a popular ingredient for icing, cordials and ice cream.

This activity was adapted from Krampf's Experiment of the Week [external link].

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