TRICHLOROETHYLENE

Introduction

Trichloroethylene (TCE) is a volatile, chlorinated organic compound. It is a clear, colorless, non-flammable liquid with a sweet odor and a characteristic chloroform-like taste. In the past, it was used as a food additive, primarily as a solvent for decaffeinating coffee and for extracting flavors and other compounds.

However, due to significant health and environmental concerns, this use has been completely discontinued and banned for decades. Its mention in a food additives list would be for historical context, as it is no longer permitted in any major food market. Today, TCE is used almost exclusively as an industrial degreasing solvent for metal parts.

CAS Number

79-01-6

Synonyms

• TCE
• Trichloroethene
• 1,1,2-Trichloroethylene
• Ethylene trichloride
• Tri-Clene

Topic Headings

1. Historical Food Applications (list form)

• Decaffeination of coffee — Used as a solvent to extract caffeine from unroasted coffee beans (Swiss Water Process is now used).
• Flavor extraction — Used to isolate and concentrate flavors from natural sources like herbs and spices.
• Extraction solvent — Employed in some food processing operations for extracting oils, fats, and waxes.

2. Mechanism of Action as an Extraction Solvent (paragraph form)

TCE was valued as an extraction solvent because of its excellent solubilizing properties for non-polar organic compounds like caffeine, oils, and fats. In the decaffeination process, unroasted green coffee beans would be steamed and then rinsed with a TCE solution. The solvent would selectively dissolve the caffeine from the beans without extracting many of the flavor compounds. The TCE-caffeine solution would then be removed, and the beans would be re-steamed to drive off any residual solvent. This process was efficient and cost-effective.

3. Physical and chemical properties (list form)

• Appearance — Clear, colorless liquid.
• Odor — Sweet, chloroform-like odor.
• Molecular weight — 131.39 g/mol.
• Boiling point — 87°C.
• Vapor pressure — High (makes it volatile, giving off fumes at room temperature).
• Solubility — Very low in water (0.1 g/100 mL) but miscible with many organic solvents.
• Stability — Decomposes when exposed to light, air, and high temperatures.

4. Safety and Regulatory Status (paragraph form)

Trichloroethylene is no longer permitted as a food additive in the United States, European Union, or most other developed nations. The FDA banned its use in food in 1977, and the EU has also prohibited its use as a food extraction solvent. It is classified as a hazardous substance due to its potential to cause serious health issues. TCE is a known central nervous system depressant, a potential carcinogen (linked to kidney cancer), and a suspected liver and reproductive toxicant. It is also an environmental pollutant and can contaminate groundwater. Due to these risks, it has been replaced by safer alternatives like ethyl acetate, supercritical carbon dioxide, or the Swiss Water process for decaffeination.