Yes, it happens. Because greener fennel sells for more, some paler or older seed has been coloured to look fresh and green. The practice is not permitted, and synthetic dyes on food can make a shipment unsaleable in your market.
You can screen for it with simple tests, but only a lab test for synthetic colours gives an answer you can rely on.
Why it happens
Green colour is one of the main things that sets fennel price. Seed that has turned yellow through late harvest, sun drying, rain or age loses value. Colouring it is a cheap way to pass it off as a higher grade.
It is more common in loose domestic trade than among processors with export customers, but no source is immune. A price that looks too good for the colour is a reason to ask questions.
Simple checks
These are a first screen only. A clean result does not prove the seed is free of colour.
- Put a spoonful of seed in a clear glass of water and leave it for some minutes. Green tint in the water is a warning sign.
- Rub a few seeds on wet white paper or tissue. Natural fennel should not leave a bright green mark.
- Look at the seeds closely. Colour that sits evenly on the ridges and in the grooves, or looks too uniform across the lot, can suggest coating.
- Compare with a known natural sample under the same light.
Lab testing
An NABL-accredited lab can test for synthetic colours. Ask which dyes the method screens for, because a test only finds what it looks for. Ask for the limit of detection on the report.
Test the approval sample and a sealed sample from the shipment. If you buy every season, test each new lot. The guide on reading a lab certificate helps you check the report.
Contract protection
- Write "no added colour of any kind" into the specification.
- Ask for a test report for synthetic dyes from an accredited lab with each lot.
- Hold a sealed retained sample from loading.
- Agree that a positive result means rejection at the supplier's cost.
- Buy from a processor whose cleaning line you have seen, not from an unknown trader.
Also check the rest
Colour fraud often goes with other quality problems, such as old seed or high admixture. When you test for dyes, check volatile oil and purity too. Our guides on avoiding spice adulteration and why green colour matters in fennel give more detail.
Where we come in
We take sealed fennel samples ourselves, send them to an NABL-accredited lab for synthetic colour tests and share the original report with you. We also check the processor's sorting line. Start with a free sourcing review.