E920 L-CYSTEINE

E920 L-Cysteine improves the quality and flexibility of the dough.
E920 L-Cysteine is also used in some specialty breads to add elasticity and a spongy texture, such as hamburger buns, pizza buns, and toast bread.
E920 L-Cysteine is also used in the pharmaceutical and cosmetic industries .

CAS Number: 52-90-4
EC Number: 200-158-2
MDL number: MFCD00064306
Linear Formula: HSCH2CH(NH2)CO2H
Molecular Formula: C3H7NO2S
Molecular Weight: 121.16 g/mol

SYNONYMS:
Cysteine, 2-Amino-3-sulfanylpropanoic acid, 2-Amino-3-sulfhydrylpropanoic acid, 2-Amino-3-mercaptopropanoic acid, (R)-2-Amino-3-mercaptopropionic acid, (2R)-2-Amino-3-sulfanylpropanoic acid, L-2-Amino-3-mercaptopropionic acid, H-Cys-OH, a-amino-b-thiolpropionic acid, L-(+)-Cysteine, (+)-2-Amino-3-mercaptopropionic acid, (2R)-2-amino-3-mercaptopropanoic acid, (2R)-2-amino-3-sulfanylpropanoic acid, (2R)-2-Amino-3-sulfanylpropansäure [German], (R)-(+)-Cysteine, (R)-2-amino-3-mercapto-Propanoic acid, (R)-2-Amino-3-mercaptopropionic acid, (R)-Cysteine, Cysteine, L-, β-Mercaptoalanine, Cystein, Cysteine, Half-cystine, L-(+)-Cysteine, L-Alanine, 3-mercapto-, Propanoic Acid, 2-amino-3-mercapto-, (R)-, Thioserine, (R)-2-Amino-3-mercaptopropanoic acid, α-Amino-β-thiolpropionic acid, (R)-Cysteine, 2-Amino-3-mercaptopropionic acid, L-Cys, (2R)-2-Amino-3-mercaptopropanoic acid, (2R)-2-Amino-3-sulfanylpropanoic acid, (R)-2-Amino-3-mercaptopropanoic acid, (2R)-2-Amino-3-mercaptopropanoate, (2R)-2-Amino-3-sulfanylpropanoate, (2R)-2-Amino-3-sulphanylpropanoate, (2R)-2-Amino-3-sulphanylpropanoic acid, (R)-2-Amino-3-mercaptopropanoate, L-2-Amino-3-mercaptopropionate, (+)-2-Amino-3-mercaptopropionic acid, (R)-(+)-Cysteine, (R)-2-Amino-3-mercapto-propanoate, (R)-2-Amino-3-mercapto-propanoic acid, (R)-Cysteine, 2-Amino-3-mercaptopropanoate, 2-Amino-3-mercaptopropanoic acid, 2-Amino-3-mercaptopropionate, 2-Amino-3-mercaptopropionic acid, 3-Mercapto-L-alanine, 52-90-4, Cystein, E920, L-Cystein, Cysteine, Half Cystine, L-Cysteine, L-Cysteine, Cysteine, L-2-Amino-3-mercaptopropionic acid, (R)-Cysteine, 2-Amino-3-mercaptopropanoic acid, β-Mercaptoalanine, Thiolalanine, Monothioglycerine amino acid, E920, INS 920

E920 L-Cysteine is an amino acid, a building block of protein, that must be obtained from food and cannot be produced by the body on its own.
E920 L-Cysteine is a beneficial and essential substance that helps remove toxins from the body, protects cells, shields the body from the harmful effects of radiation, and naturally plays a role in the treatment of some diseases.

E920 L-Cysteine (/ˈsɪstɪiːn/; symbol Cys or C) is a semiessential proteinogenic amino acid with the formula HS−CH2−CH(NH2)−COOH.
The thiol side chain in E920 L-Cysteine enables the formation of disulfide bonds, and often participates in enzymatic reactions as a nucleophile.

E920 L-Cysteine is chiral, but both D and L- Cysteine are found in nature.
E920 L-Cysteine is a protein monomer in all biota, and D-Cysteine acts as a signaling molecule in mammalian nervous systems.
E920 L-Cysteine is named after its discovery in urine, which comes from the urinary bladder or cyst, from Greek κύστις kýstis, "bladder".

E920 L-Cysteine is a naturally occurring amino acid that can also be produced synthetically or obtained from natural sources such as chicken feathers or human hair.
E920 L-Cysteine is valued in the food industry for its ability to accelerate fermentation processes and improve the texture and shelf life of bread and other bakery products.
E920 L-Cysteine is a very popular target for site-directed labeling experiments to investigate biomolecular structure and dynamics.

Maleimides selectively attach to E920 L-Cysteine using a covalent Michael addition.
E920 L-Cysteine is a semi-essential amino acid.
E920 L-Cysteine can be synthesized in the body from other amino acids, but it is also obtained through dietary sources.

E920 L-Cysteine is naturally found in protein-rich foods such as eggs, poultry, yogurt, and legumes.
E920 L-Cysteine is a sulfur-containing amino acid used in the food industry under the additive code E920.
E920 L-Cysteine naturally occurs in proteins and plays an important biological role in metabolism, detoxification, and protein structure stabilization through disulfide bond formation.

In food processing, E920 L-Cysteine helps improve dough handling properties, reduce mixing time, soften gluten structure, and enhance processing efficiency.
E920 L-Cysteine appears as a white crystalline powder with a characteristic sulfur-like odor due to its thiol group.
Industrial E920 L-Cysteine may be produced through microbial fermentation, enzymatic hydrolysis, protein extraction, or synthetic manufacturing methods.

Modern food-grade E920 L-Cysteine is increasingly produced by microbial fermentation technologies.
E920 L-Cysteine is approved for food use in many countries under regulated conditions and good manufacturing practices.
E920 L-Cysteine is an optically active form of Cysteine having L-configuration.

E920 L-Cysteine has a role as a flour treatment agent, an EC 4.3.1.3 (histidine ammonia-lyase) inhibitor and a human metabolite.
It is a E920 L-Cysteine, a L-alpha-amino acid, a serine family amino acid and a proteinogenic amino acid.
E920 L-Cysteine is a conjugate base of a L-cysteinium.

E920 L-Cysteine is a conjugate acid of a L-cysteinate(1-).
E920 L-Cysteine is an enantiomer of a D-E920 L-Cysteine.
E920 L-Cysteine is a tautomer of a E920 L-Cysteine zwitterion.

E920 L-Cysteine is an amino acid that stands out due to its natural structure and has been prominent in scientific studies.
Its presence of sulfur gives E920 L-Cysteine a significant place in the literature.
Known for its presence in protein chains, E920 L-Cysteine has been the subject of research in various sectors and has been studied for a long time.

E920 L-Cysteine, identified in the fields of chemistry and biochemistry, is frequently mentioned in scientific sources, both academically and industrially.
Known in its crystalline form, E920 L-Cysteine is also involved in various synthesis processes.

E920 L-Cysteine's widespread use in international literature demonstrates its global recognition.
E920 L-Cysteine, historically the subject of numerous biological studies, remains a focus of research today.
Modern scientific data highlight the structural properties of E920 L-Cysteine while also revealing its importance across various disciplines.

E920 L-Cysteine is an amino acid used as a flour treatment agent in baked goods to improve dough texture and processing.
E920 L-Cysteine is an amino acid used as a flour treatment agent in baked goods to improve dough texture and processing.
E920 L-Cysteine is a sulfur-containing amino acid approved as a food additive.

E920 L-Cysteine improves dough machinability and reduces kneading time in industrial baking processes.
E920 L-Cysteine in bread can be derived from human hair, duck feathers, or synthetic production.
E920 L-Cysteine is a naturally occurring amino acid found in proteins.

In bread manufacturing, E920 L-Cysteine is used as a dough conditioner (also called a reducing agent or flour treatment agent).
E920 L-Cysteine depends on the source — and the source is almost never disclosed on the label.
E920 L-Cysteine sounds innocuous — but where it comes from can make it haram.

E920 L-Cysteine is an amino acid that serves as a building block of some proteins.
E920 L-Cysteine is one of the most common reducing agents in baking, as well as in enriched beef flavors.
E920 L-Cysteine is a naturally occurring amino acid commonly used in food and pharmaceutical industries.

E920 L-Cysteine is derived from both natural and synthetic sources and is renowned for its beneficial properties.
E920 L-Cysteine improves the workability of bread and roll doughs and increases the volume of baked goods.
Previously, E920 L-Cysteine was primarily extracted from hair, horn, or feathers; today, it is produced using genetically modified bacteria.

This biotechnological process is not only more effective but also associated with less environmental impact.
E920 L-Cysteine is a sulfur-containing compound.amino acidIt is semi-essential, meaning it can be produced in the human body by conversion from methionine, another sulfur-containing amino acid.

This ability is not yet developed in infants.
E920 L-Cysteine is a component of many, especially plant-based, substances.
Proteinsand is particularly abundant in keratin, the supporting protein of, for example, horns, hair and feathers.

USES and APPLICATIONS of E920 L-CYSTEINE:
E920 L-Cysteine facilitates the quick rolling and processing of dough.
E920 L-Cysteine is most commonly used in phyllo dough flours to add elasticity and prevent tearing during rolling.
E920 L-Cysteine improves the quality and flexibility of the dough.

920 L-Cysteine is added to 1 ton of flour in amounts of approximately 4 grams, varying depending on the company's usage, and is virtually undetectable as it appears as a white powder.
Because E920 L-Cysteine is added to the flour used in ready-made phyllo dough, it indirectly finds its way into pastries and baklava.

E920 L-Cysteine is also used in some specialty breads to add elasticity and a spongy texture, such as hamburger buns, pizza buns, and toast bread.
E920 L-Cysteine is also used in the pharmaceutical and cosmetic industries .
Because E920 L-Cysteine protects the skin from the sun's harmful rays, it is used in skincare products; as an expectorant in medications and cough syrups used for lung diseases and influenza; and to support skin, hair, and nail tissue in some medications or personal care products.

E920 L-Cysteine is an amino acid used as a food additive, known primarily for its bakery-enhancing properties.
E920 L-Cysteine acts as a reducing agent that can break disulfide bonds in gluten proteins, leading to a softening of the dough and making it easier to handle.
In addition, E920 L-Cysteine improves the texture and volume of bread, which is particularly important in the production of bread and other bakery products.

The primary use of E920 L-Cysteine in the food industry is to improve the quality of bakery products, including bread, pastries, and crackers.
E920 L-Cysteine is also used in the production of certain types of pasta and in meat production, where it can serve as a protein conditioner.

E920 L-Cysteine, mainly the l-enantiomer, is a precursor in the food, pharmaceutical, and personal-care industries.
One of the largest applications of E920 L-Cysteine is the production of flavors.
For example, the reaction of E920 L-Cysteine with sugars in a Maillard reaction yields meat flavors.
E920 L-Cysteine is also used as a processing aid for baking.

In the field of personal care, E920 L-Cysteine is used for permanent-wave applications, predominantly in Asia.
Again, the E920 L-Cysteine is used for breaking up the disulfide bonds in the hair's keratin.
Site-directed spin labeling for EPR or paramagnetic relaxation-enhanced NMR also uses E920 L-Cysteine extensively.

E920 L-Cysteine is primarily used in the baking industry as a flour treatment agent and dough conditioner.
E920 L-Cysteine weakens gluten protein networks by reducing disulfide bonds, which improves dough extensibility and reduces mixing time.
This helps manufacturers achieve more consistent dough texture and increases industrial baking efficiency.

E920 L-Cysteine is commonly used in bread, rolls, pizza dough, pastries, crackers, and processed bakery products.
E920 L-Cysteine is also used in flavor production because it participates in Maillard reactions that generate meat-like and savory aromas during food processing.
In processed foods, E920 L-Cysteine may function as an antioxidant precursor and reducing agent.

Outside the food industry, E920 L-Cysteine is widely used in pharmaceuticals, cosmetics, biotechnology, and nutritional supplements.
E920 L-Cysteine is an important precursor for glutathione synthesis, one of the body’s major endogenous antioxidants.
In cosmetics, E920 L-Cysteine may be used in hair treatments, skin-care formulations, and permanent wave products because of its sulfur chemistry.

E920 L-Cysteine also has applications in biotechnology, cell culture media, fermentation technology, and pharmaceutical manufacturing.
E920 L-Cysteine may be used in medical nutrition and dietary supplements because cysteine is an important amino acid involved in protein metabolism.

E920 L-Cysteine is mainly used as a flour treatment agent, dough conditioner, processing aid, antioxidant precursor, and reducing agent in bakery applications.
In the food industry, E920 L-Cysteine is primarily used as a dough conditioner and an antioxidant.
E920 L-Cysteine is an additive that facilitates dough processing, especially in the bakery industry.

E920 L-Cysteine increases the elasticity of the flour, shortens kneading time, and creates a more homogeneous dough structure.
This results in softer, fluffier, and more durable doughs for products such as bread, bagels, and pizza.
E920 L-Cysteine, known as E920 in food technology, plays a role in flavor and aroma enhancement processes in processed foods.
E920 L-Cysteine is also known to be used as an auxiliary ingredient in some meat products and food supplements.

E920 L-Cysteine is added to the formulation of tablets and capsules in pharmaceutical production.
Due to its contribution to glutathione synthesis, E920 L-Cysteine is among the ingredients that support immunity and cell regeneration in the nutritional supplement sector.
In hair care products, E920 L-Cysteine helps strengthen hair by supporting the keratin structure.

In skin care products, E920 L-Cysteine is included in formulations due to its moisture-retaining capacity.
E920 L-Cysteine is especially commonly used in shampoos, conditioners, and face masks.
In fermentation and biochemical synthesis processes, E920 L-Cysteine can serve as a nutrient source in the growth media of microorganisms.

This increases production efficiency in industrial biotechnology applications.
In some feed formulations, E920 L-Cysteine is included as an additive to support animal nutrition and enhance protein synthesis.
E920 L-Cysteine can be particularly useful in specialized feed supplements.

In the food industry, E920 L-Cysteine is primarily used as a flour treatment agent.
E920 L-Cysteine relaxes the gluten network in dough
E920 L-Cysteine reduces mixing time

E920 L-Cysteine improves dough extensibility (stretch)
E920 L-Cysteine helps produce softer, more uniform bread at scale
E920 L-Cysteine is an amino acid used in commercial bread baking to improve dough flexibility and reduce mixing time.

-Food additive with flour enhancing role of E920 L-Cysteine:
E920 L-Cysteine is a non-essential amino acid (the human body produces it, without needing outside sources), bigger amounts being beneficial and necessary for children and the elderly.
E920 L-Cysteine has an important role in the detoxifying the body, as a result of smoking or alcohol consumption.
E920 L-Cysteine is obtained from animal protein, from hair (animal or human) and from feathers and it is added in bakery flour, improving the qualities of the dough, facilitating the processing and stabilizing the structure of the bread.

-In commercial baking, E920 L-Cysteine offers many benefits:
Gluten softening and dough relaxing
Dough conditioning
Reduced mixing and fermentation times
Better dough consistency and easier handling
Improved pan flow

-Use of E920 L-Cysteine in Food Products:
E920 L-Cysteine is primarily found in the following products:
Industrially produced bread and rolls
Biscuits and crackers
Fast-food buns and burger buns
Frozen dough and pre-baked goods
Crispbread and rusks
In the EU, E920 L-Cysteine is permitted under Regulation (EC) No. 1333/2008 for specific food categories.
The quantum satis principle applies, meaning E920 L-Cysteine may only be used in quantities technically necessary to achieve the desired effect.

-E920 L-Cysteine is used in various products and fulfills different technological tasks; for example:
E920 L-Cysteine is a component of many baking agents and baking ingredients used in the production of bread, rolls, andbaked goodsE920 L-Cysteine is widely used in all kinds of baked goods.
E920 L-Cysteine increases the "gas retention capacity," allowing baked goods to retain their volume and a light, airy texture for longer.

E920 L-Cysteine also improves the elasticity and kneadability of doughs.
E920 L-Cysteine is involved in the formation of meat and roasted aromas and is used to round off and enhance the flavor ofAromas It is used as an artificial meat flavoring and is added to vegetarian foods.

E920 L-Cysteine is also inDietary preparations, animal feed, pharmaceuticals (expectorants) and cosmetic products
Cystine is a chemically different form of E920 L-Cysteine (a disulfide of two E920 L-Cysteine molecules).
Both forms are present in creatine (hair, feathers, horn) and other natural substances.

BENEFITS AND USES of E920 L-CYSTEINE:
Amino Acid: 
E920 L-Cysteine is an essential amino acid that plays a critical role in protein synthesis and various metabolic processes in the body.

Food Additive: 
E920 L-Cysteine is widely used in the food industry as a dough conditioner, improving the texture and elasticity of baked goods, such as bread and pastries.

Dough Conditioner: 
E920 L-Cysteine helps to relax the dough, making it easier to knead and shape, resulting in better volume and texture in baked products.

Pharmaceutical Grade: 
In the pharmaceutical industry, E920 L-Cysteine is used in various formulations for its antioxidant properties and its role in promoting healthy cellular functions.

Hair Treatment: 
E920 L-Cysteine is also utilized in hair treatments and cosmetic products for its ability to strengthen hair and improve its texture and shine.

Dietary Supplement: 
As a dietary supplement, E920 L-Cysteine provides numerous health benefits, including supporting the immune system, promoting detoxification, and enhancing overall well-being.

Antioxidant: 
E920 L-Cysteine acts as a potent antioxidant, helping to protect cells from oxidative stress and damage caused by free radicals.

Protein Synthesis: 
E920 L-Cysteine is crucial for protein synthesis, aiding in the formation of various proteins and enzymes that are vital for bodily functions.

STRUCTURE of E920 L-CYSTEINE:
Like other amino acids (not as a residue of a protein), E920 L-Cysteine exists as a zwitterion.
E920 L-Cysteine has l chirality in the older d/l notation based on homology to d- and l-glyceraldehyde.
In the newer R/S system of designating chirality, based on the atomic numbers of atoms near the asymmetric carbon, E920 L-
Cysteine (and selenoE920 L-Cysteine) have R chirality, because of the presence of sulfur (or selenium) as a second neighbor to the asymmetric carbon atom.
The remaining chiral amino acids, having lighter atoms in that position, have S chirality.
Replacing sulfur with selenium gives selenoE920 L-Cysteine.

(R)-E920 L-Cysteine (left) and (S)-E920 L-Cysteine (right) in zwitterionic form at neutral pH
Dietary sources
Some foods considered rich in E920 L-Cysteine include poultry, eggs, beef, and whole grains.
In high-protein diets, E920 L-Cysteine may be partially responsible for reduced blood pressure and stroke risk.

Although classified as a nonessential amino acid, in rare cases, E920 L-Cysteine may be essential for infants, the elderly, and individuals with certain metabolic diseases or who suffer from malabsorption syndromes.
E920 L-Cysteine can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available.

CHARACTERISTICS of E920 L-CYSTEINE:
E920 L-Cysteine is one of the naturally occurring sulfur-containing amino acids.
The molecule contains a reactive thiol (-SH) group that gives E920 L-Cysteine many of its characteristic chemical properties.
E920 L-Cysteine readily forms disulfide bonds, producing cystine under oxidative conditions.
This sulfur chemistry is critically important in protein folding and structural stabilization.

E920 L-Cysteine exhibits reducing properties because the thiol group can donate electrons during chemical reactions.
In bakery applications, this reducing action helps relax gluten structures and improve dough processing behavior.

E920 L-Cysteine naturally occurs in keratin proteins found in hair, skin, nails, feathers, and wool.
Historically, some industrial E920 L-Cysteine was produced from keratin-rich materials such as hair or feathers, although fermentation-based production is now increasingly preferred.

E920 L-Cysteine plays important biological roles in detoxification pathways and antioxidant metabolism.
As a precursor to glutathione, E920 L-Cysteine contributes indirectly to cellular protection against oxidative stress.
E920 L-Cysteine is sensitive to oxidation and should be protected from excessive moisture, heat, and air exposure during storage.

E920 L-Cysteine is classified as a semi-essential amino acid because the human body can synthesize limited amounts from methionine under appropriate nutritional conditions.
E920 L-Cysteine plays a central role in protein chemistry because disulfide bridges formed from cysteine residues help stabilize protein structures.

E920 L-Cysteine is especially abundant in keratin-rich tissues such as hair and nails.
Modern biotechnology increasingly produces E920 L-Cysteine through microbial fermentation methods using genetically optimized microorganisms and carbohydrate feedstocks.

E920 L-Cysteine has attracted scientific interest because of its relationship with glutathione metabolism and oxidative stress regulation.
Derivatives such as N-acetyl-E920 L-Cysteine (NAC) are widely used in medicine and nutritional supplementation.

COMMERCIAL PRODUCTION of E920 L-CYSTEINE:
The traditional production process for E920 L-Cysteine starts with boiling the raw material (feathers or hair) in concentrated hydrochloric acid and activated carbon.
Then, this is followed by electrolysis.

One of the drawbacks of this approach is the need for huge amounts of concentrated sulfuric acid and water.
Also, the finished product is not ‘kosher’ or ‘halal’ and is unsuitable for vegan diets.

A more sustainable fermentation process for producing vegan E920 L-Cysteine and l-Cystine (a dimer of E920 L-Cysteine) has been introduced.
This uses plant-based raw materials such as corn and inorganic trace elements.
This method is more sustainable compared to the chemical extraction that uses large amounts of acid.

NUTRITION of E920 L-CYSTEINE:
E920 L-Cysteine is a semi-essential amino acid.
E920 L-Cysteine is abundant in many foods such as beef liver, crab cakes, lima beans and some mushrooms.
E920 L-Cysteine is also a component of many dietary supplements preparations.
As a reducing agent, E920 L-Cysteine may help prevent exercise-induced overproduction of free radicals.
This reduces oxidative stress.

FUNCTION of E920 L-CYSTEINE:
In dough, E920 L-Cysteine acts as a reducing agent that helps break down gluten proteins.
This dough softening effect is especially valuable in high-protein flours which often produce dense crumb and low volume products.
In high-speed bread systems, E920 L-Cysteine has the following benefits:
*Compensation for high-protein flours
*Shorter mixing times
*Lower dough temperature
*Less stressed dough

BENEFITS of E920 L-CYSTEINE:
E920 L-Cysteine improves dough handling and machinability.
E920 L-Cysteine reduces mixing and processing times in bakery manufacturing.
E920 L-Cysteine increases dough extensibility and flexibility.

E920 L-Cysteine contributes to more uniform bakery product quality.
E920 L-Cysteine enhances efficiency in industrial bread production.
E920 L-Cysteine acts as a reducing agent in food systems.

E920 L-Cysteine supports flavor generation during thermal food processing.
E920 L-Cysteine is a precursor for glutathione synthesis in biological systems.
E920 L-Cysteine demonstrates important antioxidant-related biological functions.

E920 L-Cysteine is biodegradable and naturally present in proteins.
E920 L-Cysteine supports protein structure stabilization through sulfur chemistry.
E920 L-Cysteine exhibits broad compatibility with many food and pharmaceutical systems.

BIOSYNTHESIS of E920 L-CYSTEINE:
In animals, biosynthesis begins with the amino acid serine. 
The sulfur is derived from methionine, which is converted to homocysteine through the intermediate S-adenosylmethionine. Cystathionine beta-synthase then combines homocysteine and serine to form the asymmetrical thioether cystathionine. 

The enzyme cystathionine gamma-lyase converts the cystathionine into E920 L-Cysteine and alpha-ketobutyrate. 
In plants and bacteria, E920 L-Cysteine biosynthesis also starts from serine, which is converted to O-acetylserine by the enzyme serine transacetylase. 
The enzyme E920 L-Cysteineynthase, using sulfide sources, converts this ester into L-cysteine, releasing acetate.

BIOLOGICAL FUNCTIONS of E920 L-CYSTEINE:
E920 L-Cysteineulfhydryl group is nucleophilic and easily oxidized. 
The reactivity is enhanced when the thiol is ionized, and E920 L-Cysteine residues in proteins have pKa values close to neutrality, so are often in their reactive thiolate form in the cell. 
Because of L-cysteine's high reactivity, the sulfhydryl group of E920 L-Cysteine has numerous biological functions.

Precursor to the antioxidant glutathione:
Due to the ability of thiols to undergo redox reactions, E920 L-Cysteine and cysteinyl residues have antioxidant properties. 
L-cysteine's antioxidant properties are typically expressed in the tripeptide glutathione, which occurs in humans and other organisms. 

The systemic availability of oral glutathione (GSH) is negligible; so E920 L-Cysteine must be biosynthesized from L-cysteine's constituent amino acids, cysteine, glycine, and glutamic acid. 
While glutamic acid is usually sufficient because amino acid nitrogen is recycled through glutamate as an intermediary, dietary E920 L-Cysteine and glycine supplementation can improve synthesis of glutathione.

Precursor to iron-sulfur clusters:
E920 L-Cysteine is an important source of sulfide in human metabolism. 
The sulfide in iron-sulfur clusters and in nitrogenase is extracted from cysteine, which is converted to alanine in the process.

Metal ion binding:
Beyond the iron-sulfur proteins, many other metal cofactors in enzymes are bound to the thiolate substituent of cysteinyl residues. 
Examples include zinc in zinc fingers and alcohol dehydrogenase, copper in the blue copper proteins, iron in cytochrome P450, and nickel in the [NiFe]-hydrogenases. 
The sulfhydryl group also has a high affinity for heavy metals, so that proteins containing cysteine, such as metallothionein, will bind metals such as mercury, lead, and cadmium tightly.

E920 L-Cysteine is a sulfur-containing derivative obtained from oxidation of cysteine amino acid thiol side chains. 
E920 L-Cysteine functions as an antioxidant and protects tissues against radiation and pollution, slowing the aging process. 
E920 L-Cysteine also aids protein synthesis. 
E920 L-Cysteine is abundant in many proteins of skeletal tissues and skin, and found in insulin and digestive enzymes chromotrypsinogen A, papain, and trypsinogen.

ROLES IN PROTEIN STRUCTURE OF E920 L-CYSTEINE:
In the translation of messenger RNA molecules to produce polypeptides, E920 L-Cysteine is coded for by the UGU and UGC codons.
E920 L-Cysteine has traditionally been considered to be a hydrophilic amino acid, based largely on the chemical parallel between L-cysteine's sulfhydryl group and the hydroxyl groups in the side chains of other polar amino acids. 
However, Cysteineide chain has been shown to stabilize hydrophobic interactions in micelles to a greater degree than the side chain in the nonpolar amino acid glycine and the polar amino acid serine. 

In a statistical analysis of the frequency with which amino acids appear in different chemical environments in the structures of proteins, free E920 L-Cysteine residues were found to associate with hydrophobic regions of proteins. 
Their hydrophobic tendency was equivalent to that of known nonpolar amino acids such as methionine and tyrosine (tyrosine is polar aromatic but also hydrophobic), those of which were much greater than that of known polar amino acids such as serine and threonine.

Hydrophobicity scales, which rank amino acids from most hydrophobic to most hydrophilic, consistently place E920 L-Cysteine towards the hydrophobic end of the spectrum, even when they are based on methods that are not influenced by the tendency of E920 L-Cysteine to form disulfide bonds in proteins. 

Therefore, E920 L-Cysteine is now often grouped among the hydrophobic amino acids, though E920 L-Cysteine is sometimes also classified as slightly polar, or polar.
While free E920 L-Cysteine residues do occur in proteins, most are covalently bonded to other E920 L-Cysteine residues to form disulfide bonds, which play an important role in the folding and stability of some proteins, usually proteins secreted to the extracellular medium. 

Since most cellular compartments are reducing environments, disulfide bonds are generally unstable in the cytosol with some exceptions as noted below.
Disulfide bonds in proteins are formed by oxidation of the sulfhydryl group of E920 L-Cysteine residues. 
The other sulfur-containing amino acid, methionine, cannot form disulfide bonds. 

More aggressive oxidants convert E920 L-Cysteine to the corresponding sulfinic acid and sulfonic acid. 
E920 L-Cysteine residues play a valuable role by crosslinking proteins, which increases the rigidity of proteins and also functions to confer proteolytic resistance. 
Inside the cell, disulfide bridges between E920 L-Cysteine residues within a polypeptide support the protein's tertiary structure. 

Insulin is an example of a protein with E920 L-Cysteine crosslinking, wherein two separate peptide chains are connected by a pair of disulfide bonds.
Protein disulfide isomerases catalyze the proper formation of disulfide bonds; the cell transfers dehydroascorbic acid to the endoplasmic reticulum, which oxidizes the environment. 
In this environment, E920 L-Cysteine is, in general, oxidized to cystine and are no longer functional as a nucleophiles.
Aside from its oxidation to cystine, E920 L-Cysteine participates in numerous post-translational modifications. 

The nucleophilic sulfhydryl group allows E920 L-Cysteine to conjugate to other groups, e.g., in prenylation. 
Ubiquitin ligases transfer ubiquitin to E920 L-cysteine's pendant, proteins, and caspases, which engage in proteolysis in the apoptotic cycle. 
Inteins often function with the help of a catalytic L-cysteine.
These roles are typically limited to the intracellular milieu, where the environment is reducing, and E920 L-Cysteine is not oxidized to cystine.

E920 L-CYSTEINE AND ITS FUNCTIONS IN FOODS
As a food additive, E920 L-Cysteine plays a key role in improving the quality and shelf life of bakery products while facilitating their production.
By improving the texture of the dough, E920 L-Cysteine ensures that baked goods are soft and fluffy, resulting in better consumer acceptance of the product.

ORIGIN of E920 L-CYSTEINE:
Foods rich in E920 L-Cysteine have been known for their health benefits since the Middle Ages.
Chicken macerates containing E920 L-Cysteine were often used to treat asthma.
Drugs based on derivatives are still used today for asthma and other chronic obstructive pulmonary diseases (COPD).

While E920 L-Cysteine can be derived from animal and even human sources such as goose and duck feathers, human hair, swine bristles, and hooves, there is also a well-established fermentation process using plant starch as raw material.

HISTORY of E920 L-CYSTEINE:
In 1884 German chemist Eugen Baumann found that reduction of cystine with zinc gave monomer, which he named "cysteïne".
The easy redox interconversion of E920 L-Cysteine and cystine has "provided more puzzles to protein chemists than any of the other amino acids"

INDUSTRIAL SOURCES of E920 L-CYSTEINE:
The majority of E920 L-Cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair.
Despite widespread rumor, human hair is rarely a source material.
Indeed, food additive or cosmetic product manufactures may not legally source from human hair in the European Union.
Some animal-originating sources of E920 L-Cysteine as a food additive contravene kosher, halal, vegan, or vegetarian diets.
To avoid this problem, synthetic E920 L-Cysteine, compliant with Jewish kosher and Muslim halal laws, is also available, albeit at a higher price.
The typical synthetic route involves fermentation with an artificial E. coli strain.

CHEMICAL REACTIONS of E920 L-CYSTEINE:
Being multifunctional, E920 L-Cysteine undergoes a variety of reactions.
Much attention has focused on protecting the sulfhydryl group.
Methylation of E920 L-Cysteine gives S-methylE920 L-Cysteine.
Treatment with formaldehyde gives the thiazolidine thioproline.
With phosgene and related carbonylating agents, E920 L-Cysteine gives proE920 L-Cysteine.
E920 L-Cysteine forms a variety of coordination complexes upon treatment with metal ions.
This coordination behavior is seen in many metal-E920 L-Cysteine metalloenzymes.

MECHANISM OF ACTION of E920 L-CYSTEINE:
E920 L-Cysteine contains a reactive thiol group (-SH) that is capable of cleaving disulfide bonds within the gluten network of dough.
This loosens the gluten structure, making the dough softer and more extensible, which greatly facilitates machine processing.
As a result, industrial kneading time is significantly reduced and the uniformity of baked goods is improved.

ORIGIN AND PRODUCTION of E920 L-CYSTEINE:
E920 L-Cysteine can be obtained from various sources:

Animal sources: 
Traditionally, E920 L-Cysteine was extracted from pig bristles or poultry feathers through hydrolysis.

Plant-based and microbial sources: 
Today, E920 L-Cysteine is increasingly produced through microbial fermentation or chemical synthesis, which is particularly relevant for vegetarian and vegan products.

Human hair: 
In some countries outside the EU, E920 L-Cysteine has historically been derived from human hair, though this is not permitted in the European Union.
Consumers who wish to know the exact source of E920 L-Cysteine in a product should contact the manufacturer directly, as the origin does not have to be stated on the ingredient list.

FUNCTIONALITY OF E920 IN FOOD PRODUCTS
Dough Conditioning
One of the most common uses of E920 L-Cysteine, is in the production of bread and bakery products.
E920 L-Cysteine facilitates the dough-making process by breaking down the gluten structure, leading to improved dough elasticity and extensibility.
This results in a finer crumb texture, better volume, and optimal rise during baking.

Antioxidant Properties
E920 L-Cysteine is recognized for its antioxidant capabilities.
E920 L-Cysteine helps in preventing the oxidation of fats and oils in food products, which can lead to rancidity and spoilage.
By extending the shelf life of perishable products, E920 L-Cysteine plays a vital role in food preservation.

Flavor Enhancement
In addition to its functional roles, E920 L-Cysteine can also contribute to flavor enhancement.
By influencing the Maillard reaction—an essential process during baking—E920 L-Cysteine helps develop rich, savory flavors in culinary products.

PHYSICAL and CHEMICAL PROPERTIES of E920 L-CYSTEINE:
Molecular Weight: 121.16
Appearance Form: solid
Odour: No data available
Odour Threshold: No data available
pH: No data available
Melting point/freezing point:
Melting point/range: 240 °C - dec.

Initial boiling point and boiling range: No data available
Flash point: No data available
Evaporation rate: No data available
Flammability (solid, gas): The product is not flammable. - Flammability (solids)
Upper/lower flammability or explosive limits: No data available
Vapour pressure: No data available
Vapour density: No data available
Relative density: No data available

Water solubility: soluble
Partition coefficient: n-octanol/water
log Pow: -3,05 - Bioaccumulation is not expected., (ECHA)
Auto-ignition temperature: 292 °C - Relative self-ignition temperature for solids
Decomposition temperature: > 203 °C -
Viscosity: No data available
Explosive properties: No data available
Oxidizing properties: No data available

Other safety information
No data available
Min. Purity Spec:    99%
Spectra: LCMS, FT-IR, HPLC, Polarimetry
Physical Form (at 20°C): White crystalline powder
Melting Point: 220°C
Optical Rotation: +8.75° (c=12, 2N HCl)
Long-Term Storage: Store long-term in a cool, dry place
Average mass: 121.158 Da
Monoisotopic mass: 121.019745 Da

CAS No: 52-90-4
Chemical Formula : C3H7NO2S​​​​
Molecular Weight: 121.16 g/mol
Appearance: White Crystal
Density: 1.68 g/ cm³
Chemical Name: L-Cysteine
Food Additive Code: E920
INS Number: 920
CAS Number: 52-90-4

EC Number: 200-158-2
Molecular Formula: C3H7NO2S
Molecular Weight: 121.16 g/mol
Chemical Family: Sulfur-containing amino acid
Appearance: White crystalline powder
Odor: Slight sulfur or thiol odor
Taste: Slightly acidic or sulfurous
Physical State: Solid

Chemical Name: L-Cysteine
Molecular Formula: C3H7NO2S
Molecular Weight: 121.16 g/mol
CAS Number: 52-90-4
EC Number: 200-158-2
Appearance: White crystalline powder or crystals
Odor: Characteristic sulfur-like odor
Taste: Slightly acidic taste

Physical State: Solid
Density: Approximately 1.33 g/cm³
Melting Point: Approximately 220°C with decomposition
Boiling Point: Decomposes before boiling
Solubility in Water: Freely soluble
Solubility in Ethanol: Slightly soluble
Solubility in Ether: Insoluble

pH: Slightly acidic in aqueous solution
Optical Rotation: Optically active L-isomer
Thermal Stability: Moderate under dry conditions
Oxidation Sensitivity: Easily oxidized to cystine
Reducing Properties: Strong reducing agent
Flammability: Non-flammable under standard conditions
Explosive Properties: None under normal conditions
Hygroscopicity: Slightly hygroscopic

Vapor Pressure: Negligible
Chemical Reactivity: Reactive thiol group
Crystal Structure: Orthorhombic crystalline form
Shelf Stability: Good under dry and protected conditions
Compatibility: Compatible with many food systems
Corrosiveness: Low
Biodegradability: Biodegradable
Antioxidant Potential: Indirect antioxidant precursor
Sulfur Content: Contains thiol functional group
Chelating Capacity: Moderate metal-binding properties

FIRST AID MEASURES of E920 L-CYSTEINE:
-Description of first-aid measures
*General advice:
Show this material safety data sheet to the doctor in attendance.
*If inhaled:
After inhalation: 
Fresh air.
*In case of skin contact: 
Take off immediately all contaminated clothing. 
Rinse skin with
water/ shower.
*In case of eye contact:
After eye contact: 
Rinse out with plenty of water. 
Call in ophthalmologist. 
Remove contact lenses.
*If swallowed:
After swallowing: 
Immediately make victim drink water (two glasses at most). 
Consult a physician.
-Indication of any immediate medical attention and special treatment needed.
No data available

ACCIDENTAL RELEASE MEASURES of E920 L-CYSTEINE:
-Environmental precautions:
Do not let product enter drains.
-Methods and materials for containment and cleaning up:
Cover drains. 
Collect, bind, and pump off spills. 
Observe possible material restrictions. 
Take up dry. 
Dispose of properly. 
Clean up affected area.

FIRE FIGHTING MEASURES of E920 L-CYSTEINE:
-Extinguishing media:
*Suitable extinguishing media:
Carbon dioxide (CO2) 
Foam 
Dry powder
*Unsuitable extinguishing media:
For this substance/mixture no limitations of extinguishing agents are given.
-Further information:
Prevent fire extinguishing water from contaminating surface water or the ground water system.

EXPOSURE CONTROLS/PERSONAL PROTECTION of E920 L-CYSTEINE:
-Control parameters:
--Ingredients with workplace control parameters:
-Exposure controls:
--Personal protective equipment:
*Eye/face protection:
Use equipment for eye protection. 
Safety glasses
*Body Protection:
protective clothing
*Respiratory protection:
Recommended Filter type: Filter A 
-Control of environmental exposure:
Do not let product enter drains.

HANDLING and STORAGE of E920 L-CYSTEINE:
-Conditions for safe storage, including any incompatibilities:
*Storage conditions:
Tightly closed. 
Dry.

STABILITY and REACTIVITY of E920 L-CYSTEINE:
-Chemical stability:
The product is chemically stable under standard ambient conditions (room temperature).
-Possibility of hazardous reactions:
No data available