L-Cysteine HCl

L-Cysteine HCl is the hydrochloride monohydrate salt of L-cysteine, the sulphur-containing proteinogenic amino acid that carries a free thiol (-SH) group. The salt form is the working commercial article because free-base L-cysteine oxidises readily to L-cystine, while the hydrochloride monohydrate is stable, far more water-soluble (roughly 650 g/L at 20 °C) and easier to dose into aqueous systems. Thovek supplies material meeting Ph. Eur. monograph 0895 and the USP monograph, with assay of 98.5-101.0% (Ph. Eur.) or 98.5-101.5% (USP) on the dried basis, specific optical rotation of +5.5° to +7.0°, loss on drying of 8.0-12.0% corresponding to the water of crystallisation, and sulphated ash not more than 0.1%. Origin is the first question most buyers ask. Historically around 90% of world L-cysteine was recovered by strong-acid hydrolysis of keratin from human hair, poultry feathers or hog bristle, which rules the material out for vegan, kosher and halal positioning and was restricted for food use in the EU. Since Wacker commercialised a microbial fermentation route in 2001 using corn-derived sugar as the carbon source, a genuinely plant-based supply chain has existed; EFSA has separately assessed L-cysteine hydrochloride monohydrate produced by fermentation with Escherichia coli K-12 strains. Thovek quotes fermentation-derived material by default and supplies the origin declaration, BSE/TSE statement and kosher/halal documentation with each lot so brands can substantiate a non-animal label. The compound is a nutrient amino acid and a direct biosynthetic precursor to glutathione, and its industrial uses follow from its two reactive groups. In bakery it acts as a reducing agent on gluten disulphide bonds (EU food additive E920, a flour treatment agent) to shorten mixing and proof times and improve dough machinability. In savoury flavour manufacture it is the classic sulphur donor in Maillard reaction systems that generate meat and poultry notes with reducing sugars. It is also a standard component of cell culture and fermentation media, of parenteral and enteral amino-acid formulations, and of hair, nail and sports nutrition blends. Correct classification for export is HS 2930 90 99 - organo-sulphur compounds - not the amino-acid heading 2922.