Tea and coffee

Common adulterants

• Clay (coffee powder) — Bulking material.
• Chicory powder (coffee) — Named in DART as a mixing agent; where chicory is present it must be declared.
• Exhausted tea leaves; coal-tar colour (tea) — Colour not permitted; misrepresents quality.
• Iron filings (tea) — Foreign matter.

Warning signs

• Particles settling at the bottom of a glass of coffee solution (clay)
• Coffee that sinks rather than floats (chicory)
• Coloured streaks on wet filter paper (coal-tar colour)
• Iron filings clinging to a magnet passed through tea

Home checks

• Clay in coffee powder: Stir half a teaspoon of coffee powder in a transparent glass of water for a minute and leave for five minutes. Pure coffee leaves no clay particles at the bottom. (Indicative only. A household test can give a false positive or false negative, and it cannot tell you the amount present or whether the food meets the legal standard. Only testing by an accredited laboratory confirms adulteration.)
• Chicory in coffee: Add a teaspoon of coffee powder to a glass of water. Coffee powder floats; chicory begins to sink. (Indicative only. A household test can give a false positive or false negative, and it cannot tell you the amount present or whether the food meets the legal standard. Only testing by an accredited laboratory confirms adulteration. Many people knowingly buy coffee-chicory blends; the pack should declare the chicory content.)
• Coal-tar colour in tea: Spread tea leaves on a filter paper, sprinkle water and rinse under a tap. Pure tea does not stain; coal-tar colour stains the paper immediately. A second method sprinkles tea dust on slaked lime; red, orange or other colours spreading indicate coal-tar colour. (Indicative only. A household test can give a false positive or false negative, and it cannot tell you the amount present or whether the food meets the legal standard. Only testing by an accredited laboratory confirms adulteration.)
• Iron filings in tea: Move a magnet through the tea leaves on a plate. Iron filings stick to the magnet if present. (Indicative only. A household test can give a false positive or false negative, and it cannot tell you the amount present or whether the food meets the legal standard. Only testing by an accredited laboratory confirms adulteration.)

Laboratory testing

To confirm adulteration, a sample must be analysed by a food testing laboratory using standard methods. A purchaser can have food analysed by a Food Analyst for a fee under section 40 of the Food Safety and Standards Act, 2006, but must tell the seller at the time of purchase; you can also report to the food safety authority, whose officers draw official samples. See the Food testing page for official lab directories.