For the EU, dehydrated onion is usually tested with a multi-residue screen that covers several hundred pesticides using LC-MS/MS and GC-MS/MS. Buyers often add single-residue tests for compounds the screen does not catch, such as dithiocarbamates, chlorate and ethylene oxide.
Results are judged against EU maximum residue levels (MRLs) set under Regulation (EC) No 396/2005. MRLs change, so check current values in the EU pesticides database for each result.
How EU MRLs apply to a dried product
Most EU MRLs are set for the fresh crop. For dried onion, the law allows for the concentration that happens when water is removed. A processing factor is used to convert the dried result back to a fresh basis before comparing it with the MRL.
Agree the processing factor with your lab and your customer before you test. Different factors give different answers, and arguments over the factor are common in claims. Where no MRL is set for a pesticide on onion, a default low limit applies, so traces of unapproved substances can fail.
What a typical test plan includes
- Multi-residue screen: a broad panel of insecticides, fungicides and herbicides by LC-MS/MS and GC-MS/MS.
- Dithiocarbamates: measured as carbon disulphide by a separate method. Onion family crops can give natural background readings, so ask your lab how they interpret results.
- Chlorate and perchlorate: can come from chlorinated wash water as well as from pesticides. Relevant because onions are washed before drying.
- Ethylene oxide and 2-chloroethanol: to confirm no ETO treatment. See our article on ETO and EU rejections.
- Glyphosate and other polar pesticides: need their own method, if your customer asks for them.
- Fumigant residues such as phosphine or bromide: if the product or store may have been fumigated.
Where residues come from in onion
- Field spraying of onion crops against pests and diseases.
- Treatments in onion storage.
- Wash water and sanitising agents in the plant.
- Fumigation of stores, containers or finished goods.
- Cross contamination from other crops handled in the same plant.
Controls to put in your contract
- Product must comply with EU MRLs at the time of import.
- No ETO treatment, with tests for ethylene oxide and 2-chloroethanol.
- A named test panel, method and lab accreditation for each lot.
- Sampling by an independent party from the actual lot, not from a sample the supplier chooses.
- The right to reject or claim if a test at destination fails.
Official checks at the EU border
The EU sometimes places certain products from certain countries under increased official checks at the border. The list is reviewed regularly. Check the current list with your control authority or broker before each season. Our guide to reading a lab certificate helps you check what a report really covers.
How we help
We take sealed samples from the actual lot, send them to an NABL-accredited lab with the panel you need, and share the original reports before you pay the balance. To build an EU-ready test plan, ask for a free sourcing review.