L-Cysteine monohydrochloride
52-89-1 · (1R)-1-carboxy-2-sulfanylethan-1-aminium chloride · (2R)-2-amino-3-mercapto-propionic acid · (2R)-2-amino-3-sulfanyl-propanoic acid;hydrochloride · (2R)-2-Amino-3-sulfanylpropanoic acid hydron chloride hydrate · (2R)-2-amino-3-sulfanylpropanoic acid;hydrochloride · (R)-2-Amino-3-mercaptopropanoic acid hydrochloride · (R)-2-Amino-3-mercaptopropanoicacidhydrochloride · (R)-Cysteine hydrochloride · 3-Mercaptoalanine hydrochloride · CAS-52-89-1 · CCRIS 3613 · Cystein chloride · Cysteine (as hydrochloride) · Cysteine chlorhydrate · Cysteine HCl · Cysteine HCl (anhydrous) · CYSTEINE HYDROCHLORIDE · Cysteine hydrochloride (anhydrous) · CYSTEINE HYDROCHLORIDE (II) · CYSTEINE HYDROCHLORIDE (USP MONOGRAPH) · CYSTEINE HYDROCHLORIDE ANHYDROUS (II) · CYSTEINE HYDROCHLORIDE MONOHYDRATE · CYSTEINE HYDROCHLORIDE MONOHYDRATE (EP IMPURITY) · CYSTEINE HYDROCHLORIDE MONOHYDRATE (EP MONOGRAPH) · Cysteine monohydrochloride · Cysteine, L-, hydrochloride · Cysteine, L-, monohydrochloride · cysteine-hcl · cysteine-hydrochloride · ELCYS · H-Cys-OH inverted exclamation mark currencyHCl · H-Cys-OH.HCl · L-(+)-Cysteine hydrochloride · L-2-Amino-3-mercaptopropanoic acid monohydrochloride · l-cysteine chlorhydrate · L-CYSTEINE HCl anhydrous · L-Cysteine hydro-chloride · L-Cysteine hydrochloride · L-Cysteine hydrochloride anhydrous · L-Cysteine hydrochloride, 98.0-102.0% · L-Cysteine hydrochloride, anhydrous, >=98% (TLC) · L-Cysteine hydrochloride, anhydrous, >=99.0% (RT) · L-Cysteine hydrochloride, anhydrous, from non-animal source, BioReagent, suitable for cell culture, >=98.0% · L-Cysteine hydrochloride, Vetec(TM) reagent grade, >=98% · L-Cysteine monohydrochloride · L-Cysteine, hydrochloride (1:1) · L-Cysteine--hydrogen chloride (1/1) · l-Cysteine.HCl · L-cysteinium chloride · NOURESS · (2R)-2-amino-3-sulfanylpropanoic acid hydrochloride · (R)-Cysteine HCl; (R)-1-carboxy-2-mercaptoethanaminium chloride; L-(+)-Cysteine hydrochloride · L-Cysteine monohydrochlorideCAS 52-89-1
Listed as a flour treatment agent by Canada and the US.
Listed as flour treatment agents (CA, US) · preservatives (CA) · raising agents (US) · flavour enhancers (US) · dough strengtheners (US) · nutrient supplements (US) · flavouring agents and adjuvants (US)
- Canada: Flour treatment agent — Health Canada, List of Permitted Flour Treatment Agents (List 2)
- United States: Flour treating agent — FDA, Substances Added to Food: L-CYSTEINE MONOHYDROCHLORIDE
- Canada: Preservative — Health Canada, List of Permitted Preservatives (List 11)
- United States: Leavening agent — FDA, Substances Added to Food: L-CYSTEINE MONOHYDROCHLORIDE
- United States: Flavor enhancer — FDA, Substances Added to Food: L-CYSTEINE MONOHYDROCHLORIDE
- United States: Dough strengthener — FDA, Substances Added to Food: L-CYSTEINE MONOHYDROCHLORIDE
- United States: Dough strengtheners — 21 CFR 184.1272, citing 21 CFR 170.3(o)(6)
- United States: Nutrient supplement — FDA, Substances Added to Food: L-CYSTEINE MONOHYDROCHLORIDE
- United States: Flavoring agent or adjuvant — FDA, Substances Added to Food: L-CYSTEINE MONOHYDROCHLORIDE
L-Cysteine monohydrochloride is the stable salt form of L-cysteine, used as a dough conditioner and a nutrient. The same source question applies to it.
Where it is and isn’t permitted
| Jurisdiction | Status | Scope and limits | Citation |
|---|---|---|---|
| Australia and New Zealand | Permitted | 2 food categories no numerical limit (good manufacturing practice) Show every food category
| Food Standards Code, Schedule 15, S15—5and 1 further provisionretrieved 2026-10-17 |
| Canada | Permitted, with conditions | highest permitted level 90 mg/kg 4 permitted uses Show every permitted use
| Health Canadaand 3 further provisionsretrieved 2026-10-17 |
| European Union | No listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it. | ||
| Great Britain | No listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it. | ||
| Japan | Permitted, with conditions | Designated additive: Appended Table 1, item 184, Ｌ―システイン塩酸塩 (“L-Cysteine Monohydrochloride” in the unofficial English translation). …Designated additive: Appended Table 1, item 184, Ｌ―システイン塩酸塩 (“L-Cysteine Monohydrochloride” in the unofficial English translation). Standards for use — Specifications and Standards for Foods, Food Additives, etc. (MHW Notification No. 370 of 1959), Part II (Food Additives), F (Standards for use), entry L―システイン塩酸塩: (1) [may be used only in the foods stated; states an exception to the preceding sentence] “L―システイン塩酸塩は、パン及び天然果汁以外の食品に使用してはならない。ただし、調味の目的で使用する場合はこの限りでない。” The Japanese is the standard as published. There is no official English translation of the Notification; the English in square brackets is this site’s description of what each sentence does, not a translation of the foods or the levels. Compositional specifications for this additive, in the same Notification, are not imported and are not shown here; nor are the general rules in F 添加物一般, which apply to every additive. | Regulations for Enforcement of the Food Sanitation Act (MHW Ordinance No. 23 of 1948), Appended Table 1retrieved 2026-10-18 |
| South Korea | Permitted, with conditions | Designated food additive: Standards and Specifications for Food Additives, Part III, 1. …Designated food additive: Standards and Specifications for Food Additives, Part III, 1. 일반식품첨가물 (general food additives), L-시스테인염산염 (“L-Cysteine Monohydrochloride”, the English the Code prints beside it); the Code marks it as also usable as a nutrient fortifier; 3. 영양강화제 (nutrient fortifiers), L-시스테인염산염; nutrient: 아미노산; the Code marks it as also usable as a general food additive. Main use (주용도) of L-시스테인염산염: 밀가루개량제, 향료. Standard for use (사용기준) of L-시스테인염산염: (1) [may be used only in the foods or uses listed] “L-시스테인염산염은 아래의 식품 또는 용도에 한하여 사용하여야 한다. 1. 밀가루류 2. 과일주스 3. 빵류 및 이의 제조용 믹스 4. 착향의 목적” Standard for use (사용기준) of L-시스테인염산염: (1) [may be used only in the foods listed] “L-시스테인염산염은 아래의 식품에 한하여 사용하여야 한다. 1. 밀가루류 2. 과일주스 3. 빵류 및 이의 제조용 믹스” The Korean is the standard as published. There is no official English translation of the current Code (the English version on MFDS’s website is the 2020 edition and has no legal effect); the English in square brackets is this site’s description of what each sentence does, not a translation of the foods or the levels. Compositional specifications (Part IV) are not imported, nor are the general standards in Part II, which apply to every additive. | Standards and Specifications for Food Additives (식품첨가물의 기준 및 규격), MFDS Notification, Part III (Standards for use, by item)retrieved 2026-10-18 |
| United States | Permitted | 21 CFR 184.1272retrieved 2026-10-17 | |
| Codex Alimentarius | Not listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited. |
How much is permitted
A listing usually limits the quantity as well as the food. Only one of the forms that takes is a figure: quantum satis and good manufacturing practice permit the amount the technological effect requires and no more, which is a limit rather than the absence of one. Figures below are the range across every food category this page is listed in, and categories differ between regulators — see how much is permitted.
| Australia and New Zealand | — | 2 GMP |
|---|---|---|
| Canada | 90 mg/kg | 1 numeric limit, 2 GMP, 1 no quantity stated |
| Japan | — | 1 no quantity stated |
| South Korea | — | 1 no quantity stated |
| United States | — | 1 no quantity stated |
What it is made from
Made from L-cysteine, which may be produced by fermentation or by hydrolysing keratin from feathers or hair.
- Vegan status depends on the source
- Vegetarian status depends on the source
- May raise a halal question
- May raise a kosher question
This is not an omission. What this additive is made from is not fixed — depending on the manufacturer it may be plant, animal or microbial in origin, nobody is required to say which, and the same product can change source between production runs. Ask the manufacturer if it matters to you; a label cannot answer it.
Compare other additives on the dietary indexes.
- CAS registry number
- 52-89-1
- InChIKey
- IFQSXNOEEPCSLW-DKWTVANSSA-N
- PubChem
- CID 60960
Every name it appears under
54 recorded names. A label may use any of them.
CAS registry number
- 52-89-1
As it appears in regulation
- L-Cysteine monohydrochloride
Other names
- (1R)-1-carboxy-2-sulfanylethan-1-aminium chloride
- (2R)-2-amino-3-mercapto-propionic acid
- (2R)-2-amino-3-sulfanyl-propanoic acid;hydrochloride
- (2R)-2-Amino-3-sulfanylpropanoic acid hydron chloride hydrate
- (2R)-2-amino-3-sulfanylpropanoic acid;hydrochloride
- (R)-2-Amino-3-mercaptopropanoic acid hydrochloride
- (R)-2-Amino-3-mercaptopropanoicacidhydrochloride
- (R)-Cysteine hydrochloride
- 3-Mercaptoalanine hydrochloride
- CAS-52-89-1
- CCRIS 3613
- Cystein chloride
- Cysteine (as hydrochloride)
- Cysteine chlorhydrate
- Cysteine HCl
- Cysteine HCl (anhydrous)
- CYSTEINE HYDROCHLORIDE
- Cysteine hydrochloride (anhydrous)
- CYSTEINE HYDROCHLORIDE (II)
- CYSTEINE HYDROCHLORIDE (USP MONOGRAPH)
- CYSTEINE HYDROCHLORIDE ANHYDROUS (II)
- CYSTEINE HYDROCHLORIDE MONOHYDRATE
- CYSTEINE HYDROCHLORIDE MONOHYDRATE (EP IMPURITY)
- CYSTEINE HYDROCHLORIDE MONOHYDRATE (EP MONOGRAPH)
- Cysteine monohydrochloride
- Cysteine, L-, hydrochloride
- Cysteine, L-, monohydrochloride
- cysteine-hcl
- cysteine-hydrochloride
- ELCYS
- H-Cys-OH inverted exclamation mark currencyHCl
- H-Cys-OH.HCl
- L-(+)-Cysteine hydrochloride
- L-2-Amino-3-mercaptopropanoic acid monohydrochloride
- l-cysteine chlorhydrate
- L-CYSTEINE HCl anhydrous
- L-Cysteine hydro-chloride
- L-Cysteine hydrochloride
- L-Cysteine hydrochloride anhydrous
- L-Cysteine hydrochloride, 98.0-102.0%
- L-Cysteine hydrochloride, anhydrous, >=98% (TLC)
- L-Cysteine hydrochloride, anhydrous, >=99.0% (RT)
- L-Cysteine hydrochloride, anhydrous, from non-animal source, BioReagent, suitable for cell culture, >=98.0%
- L-Cysteine hydrochloride, Vetec(TM) reagent grade, >=98%
- L-Cysteine monohydrochloride
- L-Cysteine, hydrochloride (1:1)
- L-Cysteine--hydrogen chloride (1/1)
- l-Cysteine.HCl
- L-cysteinium chloride
- NOURESS
Systematic names
- (2R)-2-amino-3-sulfanylpropanoic acid hydrochloride
- (R)-Cysteine HCl; (R)-1-carboxy-2-mercaptoethanaminium chloride; L-(+)-Cysteine hydrochloride
Hazard reference values
No reference value for this substance in the sources we hold.
Evidence and how bodies read it
Studies, and the differing conclusions regulators drew from them, are curated rather than machine-read, and none has been written for this substance yet.
Common questions
Assembled from what is above, in the words the questions are usually asked in. Each answer is the same statement the relevant section makes, with the same citations behind it.
- What is L-Cysteine monohydrochloride?
- L-Cysteine monohydrochloride is the stable salt form of L-cysteine, used as a dough conditioner and a nutrient. The same source question applies to it.
- What is L-Cysteine monohydrochloride used for in food?
- It is listed as a flour treatment agent — the role Canada and the US assign it. This page shows every function each regulator records, with the citation for each.
- Is L-Cysteine monohydrochloride banned in Europe?
- No. L-Cysteine monohydrochloride does not appear on the EU's list of authorised food additives, which is not the same as being banned: the EU permits an additive only where it has authorised it, and usually the reason for an absence is that no one applied. The EU has made no finding against this substance. It does mean it may not be used as a food additive in the EU today.
- Where is L-Cysteine monohydrochloride permitted?
- Of the seven regulators this site reads, Australia and New Zealand, Canada, Japan, South Korea and the US permit it. Each permission is for named foods at named levels, not a blanket one; the table on this page gives them with citations.
- Is L-Cysteine monohydrochloride vegan?
- It depends on the source, and a label will not tell you. L-Cysteine monohydrochloride can be made from plant or animal material, manufacturers are not obliged to say which, and the same product can change between production runs. Anyone who needs to know has to ask the manufacturer.
Sources for this page
- anz retrieved 2026-10-17
- ca retrieved 2026-10-17
- jp retrieved 2026-10-18
- kr retrieved 2026-10-18
- ecfr retrieved 2026-10-17
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