Mirror, mirror van der Waals, who is the sweetest of them all?

Sugars. Stereoisomers. Enzymes. And the sweet secrets of sweeteners.

enantiomers are stereoisomers who are mirror images, partly thanks to van der Waals forces

1-Minute NomNom

How can we have our cake (calories) and eat it too? Why, by using sweeteners that give us all the sweetness but none – or only some – of the calories!

Home made chocolate peanut butter cheesecakeWe are able to do this because scientists and companies have taken advantage of the phenomenon of stereoisomers. To understand what they are, we start at the atomic and molecular levels.

close up - Van der Waals forces are the little dots

Visualizing van der Waals forces as little dots

The atoms in chemical compounds and molecules are joined together by a combination of covalent bondselectrostatic interactions, and van der Waals forces. Van der Waals forces are the “sum of the attractive or repulsive forces” other than those from the first two.

When two chemical compounds have the same chemical formula but their atoms are joined by the bonds and forces such that they have different structures, they are called isomers of each other i.e. same formula, different arrangement.

When this difference in structure is in 3D-space , they are called stereoisomers i.e. same formula, different 3D arrangement. When two stereoisomers are a mirror image of each other, they are called enantiomers.

glucose in nature/plants/fruitsWe can use this property to do some pretty amazing things. For example, the glucose found in nature is D-glucose e.g. in plants (see chemical diagram below – left). When we consume D-glucose, enzymes in our body have structures that are able to react with its 3D-structure, breaking it down to produce energy.

D-glucose and L-glucose are stereoisomers and enantiomers because of forces and bonds like van der Waals forces

Example of stereoisomers which are also enantiomers

Our body’s enzymes however  cannot react with D-glucose’s mirror image, L-glucose (see chemical diagram above right i.e. D-glucose and L-glucose are enantiomers). This is because L-glucose – which can be created in the lab – has a different 3D-structure. The L-glucose will hence be flushed out from the body.

van der Waals forces, covalent bonds, electrostatic interactions help to create stereoisomers and enantiomers that become our artificials sweeteners

Scientists and companies use this phenomenon to produce sweeteners to make foods that taste sweet, but are low-calorie or suitable for people with diabetes (because it is not absorbed by the body). L-glucose is however expensive to manufacture. Hence scientists have found cheaper alternatives such as L-fructose and D-tagatose.  Companies have expressed interest to use tagatose for soft drinks and diary products. And with such scientific inventions, we can certainly have our cake (and sweets) and eat it!

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photos: in order – istockphoto/Joel Sorrell; depositphotos/oneinamillionyurok.arrraumOtnaYdur

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