After L-cystine is obtained from corn starch fermentation, L-cystine [HCl]→[electrolytic reduction] L-cysteine hydrochloride [decolorization, concentration, crystallization]→ L-cysteine hydrochloride crystal decolorization, concentration, crystallization electrolysis is completed, cut off the power supply, and add 10g/L(1%) activated carbon according to the dosage. Heat to 70 ° C and keep warm for half an hour. Filter for filtrate. And concentrate it under reduced pressure until there is crystallization, stir so that the crystallization is completely precipitated, filter the crystallization, wash with 95% ethanol, vacuum drying below 60℃, to obtain L-cysteine hydrochloride without crystal water.

1. Basic Information
2. Name: L-Cysteine hydrochloride monohydrate
3. CAS Number: 7048-04-6
4. Molecular Formula: C3H7NO2S·HCl·H2O （or C3H10ClNO3S）
5. Molecular Weight: 175.64 （or 175.63）
6. Physical Properties
7. Appearance: Colorless to white prismatic crystals or white crystalline powder with a slight specific odor.
8. Melting Point: 175°C
9. Refractive Index: 6° （C=8，1mol/L HCl）
10. Solubility: Soluble in water, alcohol, ammonia, and acetic acid. Insoluble in benzene, ethyl acetate, and carbon tetrachloride. A 1M aqueous solution is clear and colorless at 20°C.
11. Optical Rotation: +6.0~+7.5° （20°C/D） （c=8，6mol/l HCl） （dried basis）
12. Vapor Pressure: <0.1 hPa （20°C）
13. PH Value: The pH value of a 1% aqueous solution is 1.7；The pH value of solid is 0.8~1.2 （100g/l，H2O，20°C）
14. Hygroscopicity: Hygroscopic
15. Stability: Stable but incompatible with strong oxidizing agents, most common metals, and hydrogen chloride.
16. Chemical Properties
17. It has reducing properties and antioxidant and non-enzymatic browning prevention effects.
18. Applications
19. Used as a fermentation promoter in flour products to accelerate gluten formation and prevent aging. It is allowed to be used in fermented flour products in China with a usage amount of 0.06g/kg.
20. Used as an additive in pharmaceuticals, food, and cosmetics. For example, as a nutritional supplement, antioxidant, and color fixative.
21. It has detoxifying effects on acrylonitrile and aromatic poisoning, prevents radiation damage, treats tracheitis and reduces phlegm, and detoxifies alcohol and its acetaldehyde in the body.
22. Safety
23. The LD50 for rats by oral administration is 3.46mg/kg.
24. Storage Condition: Store at room temperature.
25. It is incompatible with strong oxidizing agents, most common metals, and hydrogen chloride.