Spices are dried in the open, handled many times and grown in warm, humid places, so an untreated lot can carry a high load of bacteria and mould spores. Before a spice goes into ready-to-eat food it is normally treated to bring that load down. The three methods in commercial use are steam, ethylene oxide (ETO) and irradiation — and the choice decides where in the world the spice can be sold.
The three methods
| Steam sterilisation | Ethylene oxide (ETO) | Irradiation | |
|---|---|---|---|
| How it works | Short exposure to saturated or superheated steam, then rapid drying and cooling | Fumigation with a gas in a sealed chamber, followed by aeration | Exposure to gamma rays, electron beam or X-rays |
| Leaves a residue | No | Yes: ethylene oxide and 2-chloroethanol | No |
| Effect on quality | Small loss of volatile oil and colour if badly controlled; leafy herbs and fine powders are the most sensitive | Very little change in aroma and colour | Very little change at permitted doses |
| Label consequence | None | None on the label, but residues are tested at the border | Must be labelled as irradiated in most markets |
Which markets accept what
- European Union and United Kingdom: ETO is not permitted for food. Residues are judged against a limit set at the level laboratories can reliably detect (0.1 mg/kg for most spices, counted as the sum of ethylene oxide and 2-chloroethanol). Since 2020 a large number of consignments have been rejected or recalled over ETO. Steam is the accepted treatment.
- United States: ETO treatment of spices is permitted, with tolerances for ethylene oxide and for ethylene chlorohydrin. Steam-treated and irradiated spices are also sold.
- Canada, Australia, Japan, the Gulf states and others: rules differ from country to country and change. Several follow the EU in practice because international buyers do.
- Irradiation is legal for spices in many countries up to a maximum dose, but it must be declared on the label and, for the EU, done in an approved facility. Consumer resistance means few retail buyers ask for it.
If the same product may be sold in more than one region, steam sterilisation is the safe common denominator. Treat the figures above as a guide and confirm the current rule for your market before you order.
What good steam treatment looks like
- A validated process: the supplier can show the log reduction it achieves for the product, not just that "steam was applied".
- Treatment of the whole spice before grinding where possible, then grinding and packing in a clean, separated area so the product is not re-contaminated.
- Rapid drying and cooling straight after the steam, so the moisture returns to specification and the volatile oil is kept.
- Before-and-after results for total plate count, yeast and mould, Enterobacteriaceae and Salmonella, plus volatile oil and colour to prove quality was preserved.
What to write into your purchase order
- The treatment required, in words: "steam sterilised; not treated with ethylene oxide; not irradiated".
- The microbiological specification the treated product must meet.
- For Europe: an ETO test result (ethylene oxide plus 2-chloroethanol) for the lot, from an accredited laboratory.
- The quality limits that must still be met after treatment: moisture, volatile oil and colour.
- A statement of the treatment on the Certificate of Analysis for every lot.
Need a specification, a sample Certificate of Analysis or a quotation? Tell us the product, grade and quantity.
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