E920: L-cysteine

What is E920?

E920 is L-cysteine, a naturally occurring amino acid that contains sulphur. It is one of the building blocks of proteins and is found in many protein-rich foods, but as an additive it is supplied in purified form.

Origin and production

Historically, L-cysteine was extracted from keratin-rich materials such as poultry feathers and hog or human hair by hydrolysis. Today it can also be made by microbial fermentation, which yields an identical amino acid without animal raw materials.

Why is it used?

In baking, L-cysteine acts as a flour treatment agent: it relaxes gluten, making dough softer and easier to stretch and shape and shortening mixing times. That is why it appears in industrial breads, pizza bases, flatbreads, sandwiches and frozen dough products.

Vegan, vegetarian and halal

Whether E920 is vegan or vegetarian depends entirely on how it was made: fermentation-derived L-cysteine contains no animal material, whereas keratin-derived material does. Labels rarely say which, so people avoiding animal products, or seeking halal or kosher assurance, should rely on certification or ask the manufacturer.

Safety and regulation

L-cysteine is authorised in the European Union as a flour treatment agent, with its use limited to flour and certain bakery applications. It is also permitted in other jurisdictions, including the United States.

Common in