Tartaric acid is a white crystalline organic acid and an important chiral chemical found in nature in many fruits such as grapes, bananas and tamarinds.

The name 'tartaric acid' is derived from the Latin word 'tartarum', which refers to 'tartar', the sediment that forms inside wine barrels, also known as tartaric cream when wine is refined. This sediment is one of the main sources of tartaric acid.

The synthesis of tartaric acid in the laboratory can be achieved by different methods, but a common method involves the following steps:

• Fermentation: Tartaric acid can be obtained by fermenting grape juice. During the fermentation process, the tartaric acid present in the grape juice remains in the wine.
• Crystallisation: After the fermentation process, the wine is left to rest in the cold. Tartaric acid is less soluble in cold solutions, so it crystallises from the wine when it cools. These crystals are often called 'wine diamonds'.
• Purification: The crystals are collected and then purified to obtain tartaric acid. This can be done by recrystallisation, in which the crystals are dissolved in hot water and then allowed to crystallise again when the solution cools.
• Drying and packaging: The purified tartaric acid is then dried and packaged for use.

In nature, tartaric acid is synthesised by many plants, particularly grapes, through a series of biochemical reactions as part of their metabolic processes.

It appears as a white crystalline powder.

What it is used for and where

Medical

Tartaric acid has a wide range of applications in pharmaceuticals. It is a well-known cough test for assessing cough function (1), improves colon function and excretion of faecal bile acids and short-chain fatty acids.

Negative contrast agent in double-contrast X-rays, as a reagent for resolving basic racemic compounds.

Cosmetics

Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.

Fragrance. It plays a decisive and important role in the formulation of cosmetic products as it provides the possibility of enhancing, masking or adding fragrance to the final product, increasing its marketability.  The consumer always expects to find a pleasant or distinctive scent in a cosmetic product.

A recent discovery by a Japanese pharmaceutical company, however not yet confirmed by clinical studies, could help baldness sufferers. Tartaric acid, according to this manufacturer, could increase substances that promote hair growth. In this study by researchers at the University of Konkuk, Japan, tartaric acid was able to maintain the colour of dyed hair and protect hair more efficiently than succinic acid as well as increase the tensile strength of hair, decrease hair porosity and smoothen the hair surface (2).

Food

It is inexpensive, readily available and widely used in beverages and other foods. In wine, tartaric acid, the main organic acid molecule responsible for the acidity of wine, together with tannin improves its colour (3). An acidic agent in food additives labelled with the number E334 in the list of European food additives with the function of an acidity regulator.

Other uses

It is one of the main acids found in wine and plays a key role in winemaking. Tartaric acid has a sour taste and is also used as an antioxidant and flavoring in food.

Catalyst in resin finishing in polyester fabrics, sulphur removal, electroplating, acid pickling, complexing agent, screening or chelating agent in chemical analysis, reducing agent in the chemical production of mirrors, imaging agent in photography, pH value adjuster in the production of oryzanol, polishing agent in metals, metal cleaner.

Safety

Tartaric acid (E 334), sodium tartrates (E 335), potassium tartrates (E 336), sodium potassium tartrate (E 337) and calcium tartrate (E 354) are authorised as food additives according to Regulation (EC) No 1333/2008 on food additives. 

The Panel established a group ADI for l(+)‐tartaric acid and tartrates (E 334‐337 and E 354) of 240 mg/kg bw per day, expressed as tartaric acid, by applying the total uncertainty factor of 10 to the reference point of 3,100 mg sodium tartrate/kg bw per day (the highest dose tested), that is approximately 2,440 mg tartaric acid/kg bw per day. Accordingly, the current ADI of 30 mg/kg bw per day is withdrawn (4).

The most relevant studies and their abstracts have been selected for further study:

Tartaric acid studies

Typical commercial product characteristics Tartaric acid

Appearance	White crystal powder
Boiling Point	399.3±42.0°C at 760 mmHg
Melting Point	170-172°C
Flash Point	210ºC
Density	1.76
Refraction Index	1.586
Vapor Pressure	0.0±2.1 mmHg at 25°C
Vapor Density	5.18
PSA	115.06000
LogP	-1.43
Specific rotation	+12°~12.8°
Loss on drying	0.2 max
Heavy metals Pb	0.001 max
Residue on ignition	0.05 max
Oxalate C2O4	0.035 max
Sulphate SO4
As	0.0003 max
Cl	0.01 max
Chemical Safety

• Molecular Formula  C₄H₆O₆    H₂C₄H₄O₆
• Linear Formula: HO₂CCH(OH)CH(OH)CO₂H
• Molecular Weight: 150.086 g/mol
• Exact Mass     150.016434
• CAS: 87-69-4  
• UNII      4J4Z8788N8      W4888I119H
• EC Number: 205-695-6       201-766-0
• DSSTox Substance ID  DTXSID8023632      DTXSID5046986
• IUPAC  (2R,3R)-2,3-dihydroxybutanedioic acid
• InChl=1S/C4H6O6/c5-1(3(7)8)2(6)4(9)10/h1-2,5-6H,(H,7,8)(H,9,10)/t1-,2-/m1/s1
• InChl Key      FEWJPZIEWOKRBE-JCYAYHJZSA-N
• SMILES   C(C(C(=O)O)O)(C(=O)O)O
• RTECS       WW7875000
• FEMA Number: 3044
• JECFA     621
• PubChem Substance ID 329751224
• MDL number: MFCD00064207
• Beilstein Registry Number: 1725147
• NCI     C47744
• RXCUI     37578

Synonyms: 

• DL-Tartaric acid
• L-tartaric acid
• Racemic acid
• Racemic tartaric acid
• 2,3-Dihydroxysuccinic acid
• 2,3-Dihydroxybutanedioic acid
• DL-Tartrate
• Paratartaric aicd
• Paratartaric acid
• Threaric acid

References____________________________________________

(1) Ohno T, Tanaka N, Fujimori M, Okamoto K, Hagiwara S, Hojo K, Shigematsu T, Sugi T, Kanazawa H, Kunieda K, Fujishima I. Cough-Inducing Method Using a Tartaric Acid Nebulizer for Patients with Silent Aspiration. Dysphagia. 2022 Jun;37(3):629-635. doi: 10.1007/s00455-021-10313-4. 

(2) Jung, Y. J., & Lee, S. H. (2021). Effect of Post-Treatment using Succinic Acid and Tartaric Acid During Dyeing Process on Hair Conditions. Journal of Convergence for Information Technology, 11(12), 221-228.

(3) Effect of sodium sulfite, tartaric acid, tannin, and glucose on rheological properties, release of aroma compounds, and color characteristics of red wine.  Wang H, Ni ZJ, Ma WP, Song CB, Zhang JG, Thakur K, Wei ZJ.  Food Sci Biotechnol. 2018 Oct 15;28(2):395-403. doi: 10.1007/s10068-018-0492-0. 

(4) EFSA Panel on Food Additives and Flavourings (FAF); Younes M, Aquilina G, Castle L, Engel KH, Fowler P, Frutos Fernandez MJ, Fürst P, Gürtler R, Gundert-Remy U, Husøy T, Mennes W, Shah R, Waalkens-Berendsen I, Wölfle D, Boon P, Tobback P, Wright M, Aguilera J, Rincon AM, Tard A, Moldeus P. Re-evaluation of l(+)-tartaric acid (E 334), sodium tartrates (E 335), potassium tartrates (E 336), potassium sodium tartrate (E 337) and calcium tartrate (E 354) as food additives. EFSA J. 2020 Mar 11;18(3):e06030. doi: 10.2903/j.efsa.2020.6030.