L-Cystine
L-Cystine is the oxidised disulfide dimer of L-cysteine, two cysteine molecules joined through their sulphur atoms by a single S-S bond.
It is the stable storage and supply form of dietary cysteine sulphur, sold as a white to slightly yellow crystalline powder that is far easier to handle than the air-sensitive monomeric thiol.
We source bulk L-Cystine from top China manufacturers for our partners, working with several of them. The manufacturers are mostly in Hebei, Anhui and Sichuan. A smaller requirement can ship in a combined container with other ingredients.
Please send the grade you need, the volume and your destination port, and we will come back with a solution and a price.
or call +86-21-6858 0751
- Packaging
- 25 kg kraft paper bag with PE inner liner
- Function
- Amino acid
- ISO 9001
- HACCP
- Halal
- Kosher
Specifications
Grades / Types Available: Pharma Grade (EP8), Food Grade (FCCV)
| Item | Specification |
|---|---|
| Appearance | White to off-white crystalline powder |
| Assay | ≥98.5% |
| Specific Rotation [α]D20 | -215.0° to -225.0° |
| Loss on Drying | ≤0.5% |
| Residue on Ignition | ≤0.1% |
| pH (saturated solution) | 4.5–6.0 |
| Heavy Metals (as Pb) | ≤10 ppm |
| Arsenic | ≤1 ppm |
| Iron | ≤10 ppm |
| Total Plate Count | ≤1000 CFU/g |
| Ninhydrin positive substances (Pharma Grade) | Any impurity: 0.2% MAX |
| Chloride (Pharma Grade) | 200ppm MAX |
| Sulphate (Pharma Grade) | 300ppm MAX |
| Ammonium (Pharma Grade) | 200ppm MAX |
| Lead (Food Grade) | 5mg/kg MAX |
| Sulphated ash | 0.1% MAX |
Common Markets Grades
L-Cystine grades run from pharmaceutical through food and cosmetic to feed.
Pharmaceutical grade meets USP and Ph. Eur. monographs at 98.5 to 101.0 percent on the dried basis. It is used in parenteral amino acid solutions, oral pharmaceuticals, and as a substrate in chemical synthesis.
Food and supplement grade at 99 percent minimum meets FCC specifications and is produced for dietary supplements, sports nutrition, hair and nail formulations, and medical foods.
Cosmetic grade material is produced for hair-care actives, permanent wave formulations, and skin-conditioning products that build on the role of cystine disulfides in hair and nail keratin.
Feed grade material at 98 percent is produced for fur animal nutrition and specialty pet food applications.
Applications
- Parenteral nutrition amino acid solutions as a stable cysteine source
- Hair, skin, and nail dietary supplements
- Sports nutrition and recovery formulations
- Medical foods and clinical nutrition products
- Permanent wave and hair straightening cosmetic systems
- Skin-care actives in keratin-support formulations
- Cell culture media as an oxidation-stable sulphur source
- Pharmaceutical synthesis intermediate
- Specialty fur animal and pet food nutrition
- Reference standard in analytical chemistry
Brands Using L-Cystine
Widely-distributed consumer products that list L-Cystine on the ingredient label.
- Enfamil (Mead Johnson)Enfamil Nutramigen Hypoallergenic Infant Formula ↗Enfamil Nutramigen ready-to-use infant formula ingredient panel lists L-Cystine alongside L-Tyrosine, L-Tryptophan and L-Carnitine, added to supplement the extensively hydrolysed casein protein base for infants with cow's milk allergy.Label verified 2026-05-24
- Enfamil (Mead Johnson)Enfamil PurAmino Amino Acid-based Infant Formula ↗Enfamil PurAmino amino acid-based formula lists L-cystine in the amino acid blend alongside L-histidine, L-leucine, L-lysine HCl and other free-form amino acids constituting the protein equivalent of this hypoallergenic formula.Label verified 2026-05-24
Brand names, product names and logos are the property of their owners. They appear here as published evidence that the ingredient is used, taken from the brand's own label or website. Their appearance is not an endorsement, and it does not mean the brand buys from us or from any manufacturer listed on this site.
China Manufacturers of L-Cystine
Top L-Cystine manufacturers in China.
Anhui Omire Biotechnology Co., Ltd.4 ingredients in the directory
Emeishan Longteng Biotechnology Co., Ltd.10 ingredients in the directory
Hebei Harmony Amino Acid Co., Ltd.7 ingredients in the directory
Jiangsu Quanjia Shun Health Technology Co., Ltd.12 ingredients in the directory
Shijiazhuang Shixing Amino Acid Co., Ltd.7 ingredients in the directory
Xintai Jiahe Biotech Co., Ltd.（新泰市佳禾生物科技有限公司）10 ingredients in the directory
Company names and logos are the property of the manufacturers themselves. They are listed here because our own directory records them as producing this ingredient. A listing is not an endorsement by them, and we do not represent them or speak on their behalf.
How We Help Source L-Cystine
Direct Factory Sourcing
We run the whole process: selecting the manufacturer from the top Chinese food ingredient producers, negotiating the price, verifying quality, and coordinating the logistics. You deal with us instead of with several factories at once.
Original Packaging and Documents from the Manufacturer
The manufacturer sends your L-Cystine out of its own factory in the original packing, through to your destination port. The COA, COO, MSDS, TDS and any certifications reach you from the manufacturer as well.
Free Samples and Lead Time
We send 100 to 500 g free for your own laboratory to test and you cover only the courier, usually within 2 to 3 working days. ETD is usually within 7 to 15 days once the order is confirmed, and we check that date against the factory's own manufacturing schedule before we give it to you.
Combined Shipment
We can load L-Cystine together with other ingredients such as Glycine, L-Arginine and L-Leucine into one 20' FCL. If your quantity is small, we can also ship LCL.
Regulatory Status
L-Cystine is approved as a food-grade amino acid, dietary supplement ingredient, and pharmaceutical excipient in all major markets.
In the United States it is GRAS under 21 CFR 172.320 for use as a nutrient added to foods, with provisions for infant formula use under 21 CFR 107. The European Union authorises L-cystine as a permitted amino acid in foods, food supplements, and food for special medical purposes.
JECFA has reviewed L-cystine and accepts it as a food-grade amino acid without numerical limit when used in line with good manufacturing practice.
USP and Ph. Eur. monographs govern pharmaceutical use. Where the source is animal-derived (duck feather hydrolysate), suppliers issue species-of-origin and traceability documentation, while Halal, Kosher, and vegetarian certifications are typically reserved for material derived from fermentation-sourced cysteine.
Manufacturing Process
L-Cystine is produced by two main routes that mirror the supply structure for L-cysteine.
The traditional route extracts L-cystine directly from acid hydrolysates of keratin-rich materials, principally duck feathers in modern Asian production and previously human hair, pig bristles, and horn. Concentrated hydrochloric acid breaks the keratin polypeptide into free amino acids, and L-cystine precipitates selectively at its isoelectric point near pH 5 because of its very low water solubility (about 0.1 g per L at 25 degrees Celsius). Repeated recrystallisation yields a high-purity finished powder.
The fermentation route produces L-cysteine first via engineered Escherichia coli or Pantoea strains, then oxidises the cysteine to L-cystine in a controlled aerobic step or by air oxidation during downstream processing. Wacker Chemie and Ajinomoto operate the principal fermentation routes; the cystine product is filtered, washed, and dried.
Cystine is typically more economical to ship and store than the equivalent quantity of cysteine because the disulfide is air-stable, and it is often the preferred starting material for downstream conversion back to L-cysteine HCl in regional repackaging operations.
