Lactic Acid, DL-Lactic acid, Milk Acid, Ethylidene Lactic Acid, Racemic Lactic, E270, 50-21-5, 598-82-3

LACTIC ACID (C₃H₆O₃, E270)

1. Chemical Identity and Material Classification

• Chemical Name: Lactic Acid, 2-Hydroxypropanoic Acid, 2-Hydroxypropionic Acid

• Synonyms: Milk Acid, Racemic Lactic, Ethylidene Lactic Acid, DL-Lactic Acid, α-Hydroxypropionic Acid, E270

• CAS Numbers:

  • L(+)-Lactic Acid: 79-33-4

  • DL-Lactic Acid (Racemic): 50-21-5 (also 598-82-3)

  • Sodium Lactate: 72-17-3

• EC Number (EINECS): 200-018-0

• Molecular Formula: C₃H₆O₃ (CH₃–CHOH–COOH)

• Molecular Weight: 90.08 g/mol

• E Number: E270 (food additive)

• Chemical Class: Alpha-hydroxy acid (AHA), carboxylic acid

• HS Code: 2918.11

• UN Number: 3265 (Corrosive liquid, acidic, organic, n.o.s.)

2. Physical Properties

2.1 General Physical Properties

2.2 Optical Activity

2.3 Solubility in Water

2.4 Solubility in Other Solvents

2.5 Aqueous Solution Properties

3. Chemical Properties

3.1 Molecular Structure

Structure: CH₃–CHOH–COOH

• Alpha-hydroxy acid (hydroxyl group on alpha carbon)

• Carboxylic acid group (-COOH) and hydroxyl group (-OH)

• Chiral carbon → optically active (L- and D- isomers)

• Bifunctional molecule (acid and alcohol reactivity)

• Weak organic acid (pKa 3.86)

3.2 Optical Isomers (Enantiomers)

Note: L(+)-Lactic Acid is the naturally occurring form in humans and is the preferred form for food and pharmaceutical applications.

3.3 Acid Dissociation Constant (pKa)

3.4 Dimerization (Lactide Formation)

3.5 Chemical Reactivity

3.6 Thermal Stability

3.7 Stability

3.8 Incompatibilities

4. Commercial Grades and Concentrations

5. Quality Specifications (Food/Pharmaceutical Grade – 88% Solution)

6. Production Methods

6.1 Fermentation (Natural L(+)-Lactic Acid – Most Common)

Microorganism: Lactobacillus species, Bacillus coagulans, Rhizopus oryzae (fungus)

Substrate: Sugar (glucose, sucrose, lactose from corn, sugar beet, molasses, whey)

Process:

1. Substrate sterilized and inoculated with lactic acid bacteria

2. Fermentation at 30–45°C, pH controlled (5.5–6.5) with CaCO₃ or NaOH

3. Calcium lactate or sodium lactate forms

4. Acidification with H₂SO₄ → lactic acid + CaSO₄ (gypsum)

5. Purification by filtration, evaporation, activated carbon, ion exchange

Yield: 85–95%
Product: L(+)-Lactic Acid (≥ 98–99% L-isomer)

6.2 Chemical Synthesis (DL-Lactic Acid – Racemic)

Reaction: CH₃CHO (acetaldehyde) + HCN → CH₃CHOHCN → hydrolysis → CH₃CHOHCOOH + NH₃

Process:

1. Acetaldehyde reacts with hydrogen cyanide (HCN)

2. Hydrolysis with sulfuric acid

3. Purification

Product: DL-Lactic Acid (racemic mixture – 50% L, 50% D)

6.3 Carbohydrate Fermentation (Whey – Lactose)

Source: Cheese whey (by-product of dairy industry)

Process: Lactose fermented by Lactobacillus bulgaricus → L(+)-lactic acid

7. Mechanism of Action

7.1 Antimicrobial Mechanism (Food Preservation)

• Lactic acid lowers pH (acidifies the environment)

• Undissociated lactic acid (pKa 3.86) penetrates microbial cell membranes

• Dissociates inside the cell (pH ~5–6) → releases H⁺

• Lowers intracellular pH → disrupts enzyme activity, metabolism

• Inhibits growth of bacteria, yeasts, molds

Effective against: Listeria monocytogenes, E. coli, Salmonella, Clostridium botulinum, Lactobacillus (resistant)

7.2 Skin Care (Exfoliation – AHA)

• Breaks down intercellular bonds between corneocytes (dead skin cells)

• Promotes shedding of dead skin cells

• Stimulates collagen synthesis

• Improves skin hydration (increases hyaluronic acid)

• Reduces fine lines, wrinkles, hyperpigmentation

8. Industrial Applications

8.1 Food and Beverage Industry (E270 – Largest Application ~85% of production)

Food additive code: E270 – permitted worldwide (EU, USA, Codex)

8.2 Pharmaceutical Applications

8.3 Cosmetics and Personal Care

8.4 Industrial and Technical Applications

8.5 Agriculture and Animal Feed

8.6 Biodegradable Polymers (PLA – Polylactic Acid)

9. Lactate Salts – Comparison

10. Toxicology and Safety

10.1 Acute Toxicity

10.2 Special Concerns

10.3 GHS Classification (88% Solution)

10.4 NFPA Rating

11. Safety Precautions and Personal Protective Equipment (PPE)

• Hazards:

  • Corrosive – causes severe skin burns and eye damage (H314)

  • Harmful if swallowed (H302)

  • Hygroscopic – absorbs moisture from air

  • Combustible (flash point >110°C)

  • Corrosive to metals

• PPE (mandatory – for concentrated 88% solution):

  • Chemical-resistant gloves (nitrile, neoprene, or butyl rubber, EN 374)

  • Chemical splash goggles (EN 166) or full face shield

  • Protective clothing (acid-resistant apron or coverall)

  • Respiratory protection: P2 filter for mist

• Engineering controls:

  • Local exhaust ventilation (LEV) for mist control

  • Eyewash stations and safety showers

• Storage conditions:

  • Keep tightly closed in original container (HDPE, PP, stainless steel – NOT carbon steel or aluminum)

  • Store in cool, dry, well-ventilated area (5–30°C)

  • Protect from freezing (may crystallize below 18°C – warm to 20–30°C)

  • Protect from light (may discolor)

  • Store away from strong oxidizing agents and strong bases

• First aid:

  • Inhalation: Move to fresh air

  • Skin contact: Remove contaminated clothing; wash with copious water for at least 15 minutes; seek medical attention immediately

  • Eye contact: Rinse with water for at least 15 minutes, lifting eyelids; remove contact lenses; seek immediate medical attention

  • Ingestion: Rinse mouth; do NOT induce vomiting; drink water or milk; seek immediate medical attention

12. Environmental Fate

13. Storage and Shelf Life

13.1 Storage Conditions

13.2 Shelf Life

14. Transport Information

15. Synonyms and Common Names

• English: Lactic Acid, 2-Hydroxypropanoic Acid, 2-Hydroxypropionic Acid, Milk Acid, Racemic Lactic, Ethylidene Lactic Acid, E270

• French: Acide lactique

• German: Milchsäure

• Spanish: Ácido láctico

• Turkish: Laktik Asit, Süt Asidi

Trade names: Purac, Galacid, Lactic Acid 88%, L(+)-Lactic Acid

16. Lactic Acid vs. Other Acids – Comparison

17. Frequently Asked Questions (FAQs)

Q1: What is the difference between L-lactic acid and DL-lactic acid?
A1: L-Lactic acid is the naturally occurring form (produced by humans, animals, and most bacteria). It is optically active (+). DL-Lactic acid is a synthetic racemic mixture (50% L, 50% D). L-Lactic acid is preferred for food and pharmaceutical applications because humans metabolize it efficiently. D-Lactic acid is poorly metabolized.

Q2: Is lactic acid safe to eat?
A2: Yes, food-grade lactic acid (E270) is GRAS (Generally Recognized as Safe) by FDA and EFSA. It occurs naturally in many fermented foods (yogurt, cheese, sourdough bread, pickles, sauerkraut) and is used as a preservative and acidulant.

Q3: Is lactic acid gluten-free?
A3: Yes, lactic acid is gluten-free. It is produced by fermentation of carbohydrates (sugar, corn, beets) or by chemical synthesis – it contains no gluten.

Q4: Is lactic acid vegan?
A4: Yes, lactic acid produced by fermentation is vegan (non-animal origin). However, some commercial lactic acid may be derived from whey (dairy by-product) – check the source. Most industrial lactic acid is from corn or sugar fermentation (vegan).

Q5: Does lactic acid exfoliate skin?
A5: Yes, lactic acid is an alpha-hydroxy acid (AHA) that exfoliates the skin by breaking down the bonds between dead skin cells. It also stimulates collagen production and improves skin hydration.

Q6: Can lactic acid be used for descaling?
A6: Yes, lactic acid is an effective descaling agent for removing limescale (calcium carbonate) and rust. It is less corrosive than strong mineral acids (HCl, H₂SO₄) and is used in coffee makers, kettles, and industrial equipment.

18. Lactic Acid and Polylactic Acid (PLA)

19. Lactic Acid Concentration Guide

20. Summary Table – Key Specifications at a Glance

This TDS is prepared in compliance with ISO 11014-1 format and is intended for food technologists, pharmaceutical scientists, cosmetic formulators, industrial cleaning specialists, textile chemists, and procurement professionals. Certificates of Analysis (CoA), Safety Data Sheets (SDS), and sample validation reports are available upon request.