L-cysteine

L-Cysteine (CAS 52-90-4), also designated E920 in food applications, is a sulfur-containing amino acid sourced through fermentation or protein hydrolysis.

Where is L-cysteine used?

• Food and pharmaceutical manufacturing: dough conditioner and antioxidant
• Precursor in flavor and nutrient synthesis
• Commercial baking: E920 reduces mixing time and improves dough extensibility in bread, crackers, and pizza bases
• Pharmaceutical and nutraceutical: building block for glutathione synthesis and amino acid infusion formulations
• Personal care: hair treatment products
• Keratin-based straightening and conditioning systems where it modifies disulfide bonds in hair protein
• In flavor production, Cys reacts with sugars under heat to generate meat-like and savory Maillard compounds.

Good to know: Qualifies under FEMA 3263 for reaction flavor systems. The hydrochloride salt is the most commercially prevalent form due to its stability and ease of handling in industrial settings.

Commercial specifications

• Free base and hydrochloride monohydrate forms
• Grades: USP, Ph. Eur., FCC, food-grade