Tartaric Acid: A Naturally Occurring Carboxylic Acid With Numerous Applications
Chemical Properties and Structure of Tartaric Acid
Tartaric acid is an organic carboxylic acid that exists as a white, crystalline powder at room temperature. Its chemical formula is C4H6O6 and its molar mass is 150.087 g/mol. Tartaric acid contains two carboxyl groups that give it acidic properties. Its chemical structure allows it to form neutral salts called tartrates when reacted with bases or alkalis. When dissolved in water, tartaric acid forms hydrogen tartrate ions which contribute to its overall acidity.
In terms of structure, Tartaric Acid contains two chiral centers and exists in both left-handed (L-) and right-handed (D-) optical isomer configurations. The L(+) and D(-) enantiomers of tartaric acid have identical physical properties except for their ability to rotate plane-polarized light in opposite directions. In naturally occurring tartaric acid from grape wine, the L(+) enantiomer predominates.
Natural Sources and Extraction of Tartaric Acid
Tartaric acid is most notably found naturally in grapes and other fruits like tamarinds. In grapes, it is present in the highest concentration in the skin. During the winemaking process, tartaric acid accumulates in the sediment leftover after fermentation known as "wine lees" or "argol". This sediment, called argol or argol tartar, contains roughly 60% tartaric acid by mass and it was historically the primary commercial source of tartaric acid.
To extract tartaric acid from argol, the dried residue is dissolved in hot water followed by the addition of an alkali like sodium or potassium hydroxide which precipitates the tartrate salt. The precipitate is then acidified to regenerate pure tartaric acid crystals. Alternatively, calcium carbonate can be added which causes calcium tartrate to precipitate out. This calcium salt is then treated with sulfuric acid to produce insoluble calcium sulfate and solve tartaric acid.
Uses and Applications of Tartaric Acid
Given its naturally acidic nature and various beneficial properties, tartaric acid has numerous commercial uses across food, beverage, pharmaceutical, and other industries:
- Wine production: As mentioned, tartaric acid is a major component contributing to the flavor profile and acidity of wine. It helps stabilize wine color and acts as a natural preservative by inhibiting microbial growth.
- Beverages: It is used to acidify and provide a sour taste in various fruit beverages, soft drinks, and alcoholic drinks like beer. Tartaric acid balances pH and acts as a preservative in fruit juices and cordials as well.
- Bakery goods: In baked goods, it enhances volume, texture and shelf life by inhibiting starch retrogradation. It is found in many baking powders that produce carbon dioxide leavening.
- Confections: Tartaric acid is often used in candy making for its ability to prevent sugar crystallization. This allows candies to maintain a smooth, creamy texture.
- Pharmaceuticals: It is present as an inactive ingredient in many antacid preparations to counteract alkalinity. Some ointments and creams also contain it for its mildly acidic and antioxidant effects.
- Food additive: Designated as E334 on labels, it is approved for use as an acidity regulator, antioxidant and emulsifier in numerous processed foods.
- Dyeing and tanning: Historically, solutions of cream of tartar were used to set colors in textile dyeing and preserve pelts in tanning.
- Extractive metallurgy: Sodium tartrate and similar tartrates act as fluxing agents in extracting various metals like copper and lead from their ores.
- Household products: Products like baking soda substitutes, rust removers, descalers and more contain tartaric acid for its cleaning properties over a wide pH range.
Industrial Production of Tartaric Acid
While grape-based argol remains an important source, most tartaric acid is now commercially manufactured via fermentation using various fungi. Aspergillus niger is commonly employed as it can convert molasses, cornstarch or glycerol into tartaric acid through a process called ketogenesis.
Briefly, the fungus is cultured in large fermenters on a carbohydrate substrate along with necessary nutrients. During growth, it produces ketoglutaric acid which gets spontaneously oxidized and hydrated within the culture to form tartaric acid. After 7-10 days, tartrates accumulate in the fermentation broth. These are precipitated, purified and then crystallized to isolate pure tartaric acid product. Yields from fungal fermentation are higher than argol extraction methods.
To conclude, tartaric acid is a naturally derived multifunctional organic acid with broad applications in food, beverages, pharmaceuticals and other industries due to its acidifying, complexing, stabilizing and antioxidant properties. Though historically obtained from grape wine lees, modern industrial fermentation using fungi allows for cost-effective, high yield production of this valuable carboxylic acid.
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Ravina Pandya, Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. (https://www.linkedin.com/in/ravina-pandya-1a3984191)
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