Aspartame

How it's made

Synthesised from two amino acids (phenylalanine, aspartic acid).

Aspartame is an intense artificial sweetener about 200 times sweeter than sugar, used in diet drinks, sugar-free desserts, yoghurts and tabletop sweeteners. Unlike some sweeteners it is not heat-stable enough for most baking, and it provides negligible calories because so little is needed.

It is made from two amino acids — aspartic acid and phenylalanine — which are the normal building blocks of protein. These are joined together (with the phenylalanine part modified as a methyl ester) through a controlled chemical and/or enzymatic synthesis, producing the aspartame molecule. The amino acids themselves are typically made by fermentation.

The aspartame is purified and crystallised into a white powder. Because it contains phenylalanine, products must warn people with the rare inherited condition phenylketonuria (PKU), who cannot process it. For everyone else the body simply digests it like the proteins it is built from; it is one of the most extensively studied of all food additives.