L-cysteine (E920)

Purpose and Function

L-cysteine (E920) is a non-essential amino acid widely used in the food industry for its multifunctional properties. It serves as a flavoring agent, leavening agent, and dough conditioner. In baking, L-cysteine is particularly valued for its ability to break down disulfide bonds in gluten, which improves dough elasticity and reduces mixing time. This makes it a key ingredient in the production of baked goods like bread, biscuits, and pastries, where it enhances texture and volume.

Beyond its role in food, L-cysteine is also used in pharmaceuticals as a detoxifying agent and in cosmetics for its antioxidant properties. It is often derived from natural sources such as human hair, duck feathers, or synthetic processes, with the latter being more common in modern production due to ethical and safety concerns.

Potential Risks and Side Effects

While L-cysteine (E920) is generally recognized as safe (GRAS) by regulatory bodies like the FDA and EFSA, there are some concerns regarding its safety and sourcing. Synthetic L-cysteine is considered safer, but the use of animal-derived L-cysteine, particularly from human hair or feathers, raises ethical and potential contamination issues. Some studies suggest that excessive consumption of L-cysteine may lead to adverse effects, including gastrointestinal discomfort, nausea, and headaches.

A study published in PMC (https://pmc.ncbi.nlm.nih.gov/articles/PMC6017824/) highlights that while L-cysteine is beneficial in moderate amounts, high doses could potentially disrupt amino acid balance in the body. Additionally, individuals with specific health conditions, such as cystinuria (a genetic disorder affecting cysteine metabolism), should avoid excessive intake of L-cysteine to prevent complications.