Lactic acid
[CAS# 50-21-5]

Identification

• Classification: API >> Synthetic anti-infective drugs >> Disinfectant antiseptic
• Name: Lactic acid
• Synonyms: DL-Lactic acid; 2-Hydroxypropanoic acid
• Molecular Formula: C₃H₆O₃
• Molecular Weight: 90.08
• CAS Registry Number: 50-21-5
• EC Number: 200-018-0
• SMILES: CC(C(=O)O)O

Properties

• Density: 1.209
• Melting point: 18 °C
• Boiling point: 122 °C (15 mmHg)
• Refractive index: 1.4252-1.4272
• alpha: -0.05 ° (c= neat 25 °C)
• Water solubility: SOLUBLE

Safety Data

• Hazard Symbols: GHS05;GHS07 Danger
• Risk Statements: H315-H318
• Safety Statements: P264-P264+P265-P280-P302+P352-P305+P354+P338-P317-P321-P332+P317-P362+P364

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Serious eye damage	Eye Dam.	1	H318
Skin irritation	Skin Irrit.	2	H315
Skin corrosion	Skin Corr.	1C	H314
Eye irritation	Eye Irrit.	2	H319
Skin corrosion	Skin Corr.	1B	H314
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Specific target organ toxicity - single exposure	STOT SE	3	H335
Reproductive toxicity	Repr.	2	H361
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Skin corrosion	Skin Corr.	1	H314
Acute toxicity	Acute Tox.	3	H331
Skin corrosion	Skin Corr.	1A	H314

• Transport Information: UN 1760

Discovery and Applications

Lactic acid was discovered by Swedish chemist Carl Wilhelm Scheele in 1780. He isolated lactic acid from yogurt and observed its formation during bacterial fermentation of lactose. Lactic acid occurs naturally in dairy products, fermented vegetables, and as a byproduct of anaerobic respiration in muscle tissue during intense exercise. Commercial production of lactic acid involves either microbial fermentation or chemical synthesis. The fermentation process typically uses lactobacilli to convert carbohydrates into lactic acid. This approach is favored because it is environmentally sustainable and produces optically pure lactic acid, which is critical for specific applications.

Lactic acid is widely used in the food industry as a preservative and flavoring agent. Its antimicrobial properties help extend the shelf life of a variety of products, including dairy products, pickled vegetables, and fermented foods such as sauerkraut and kimchi. It imparts a rich flavor and enhances the mouthfeel of foods and beverages.

In food processing, lactic acid acts as a pH regulator to improve the texture and stability of products. It is essential in the production of baked goods, helping to control acidity and promote dough expansion.

In the pharmaceutical industry, lactic acid is utilized for its biocompatibility and non-toxicity. It is an ingredient in intravenous fluids used to treat acidosis and electrolyte imbalances. Its role in drug formulations extends to serving as a pH adjuster and stabilizer, ensuring the effectiveness and safety of medications.

Lactic acid is a key ingredient in skincare products, performing exfoliating and moisturizing properties. As an alpha hydroxy acid (AHA), it helps remove dead skin cells, promoting smoother, brighter skin. Its ability to enhance skin moisturization makes it a popular choice in lotions, creams, and exfoliators.

An important application of lactic acid is in the production of polylactic acid (PLA), a biodegradable plastic. PLA is used in packaging, disposable cutlery, and medical implants, offering an environmentally friendly alternative to conventional plastics. PLA's biodegradability is in line with efforts to reduce plastic waste and promote sustainable practices.

Lactic acid is used in dyeing and tanning processes in the textile and leather industries. It helps soften and condition materials, improving their quality and durability. In textile dyeing, lactic acid helps fix colors, ensuring vibrant, long-lasting results.

Lactic acid can be safely applied to food and pharmaceuticals when used within regulatory guidelines. Its biodegradability and low toxicity make it environmentally friendly. However, handling of concentrated lactic acid requires care to prevent skin irritation and epidermal injury.

References

2020. Lactic Acid Production and Its Application in Pharmaceuticals. Bioactive Natural products in Drug Discovery.
DOI: 10.1007/978-981-15-1394-7_16

1990. Contribution of exogenous substrates to acetyl coenzyme A: measurement by carbon-13 NMR under non-steady-state conditions. Biochemistry.
DOI: 10.1021/bi00481a002

1990. THE COLON, THE RUMEN, AND D-LACTIC ACIDOSIS. Lancet (London, England).
DOI: 10.1016/0140-6736(90)93397-8