Yes, almost always microbiological testing, and often sterilisation too. Dried herbs are grown in open fields, dried in the open or in simple dryers, and handled by hand, so they can carry high bacterial counts, moulds and sometimes Salmonella.
Whether you need sterilisation depends on what your customer does next. If the herb goes into a ready-to-eat product, a tea or a supplement without further heat treatment, a sterilised grade is usually required.
What labs usually test
The exact list depends on your market and product. A typical panel for dried herbs includes these.
- Total plate count, also called aerobic plate count.
- Yeast and mould.
- Enterobacteriaceae or coliforms, as a hygiene indicator.
- E. coli.
- Salmonella, usually as absent in a set weight such as 25 g.
- Sometimes Bacillus cereus, Clostridium perfringens or Staphylococcus aureus, if your customer asks.
Sterilisation options
Steam sterilisation is the usual method for EU, UK and US buyers. Saturated steam cuts the microbial load, then the product is dried and cooled. Our guide to steam sterilisation explains the process.
Leafy herbs are harder to steam than seeds. Leaves can darken, lose aroma or clump if the process is too hot or too wet. Ask the supplier which herbs they have steamed before and request a sterilised sample, not a raw one.
Ethylene oxide is not permitted on food in the EU, and residues even at trace levels fail. Write "no ETO treatment" into the spec and test for ethylene oxide and 2-chloroethanol. Our article on ETO treatment and EU rejections has the background. Irradiation is another option in some markets, but it is restricted and must be labelled in the EU.
Testing before and after
Sterilisation is only as good as what happens after it. A sterilised herb packed in a dusty room or in reused bags can pick up bacteria again. Test after packing, not only after the steam unit.
Draw samples from several bags in the lot. Microbes are not spread evenly, so one bag can pass while another fails. Salmonella in particular can appear in small pockets.
Ask for the certificate to name the lot, the test methods and the lab's accreditation. A supplier's in-house result is useful for their own control, but it is not proof for you.
Setting limits
Microbial limits are not the same everywhere. Some come from law, such as Salmonella rules, and some from your customer's spec. Raw and sterilised grades need different limits. Agree both in writing before sampling, so the supplier knows which grade to send.
If you sell into supplements or herbal medicines, pharmacopoeia limits may apply instead of food limits. Check which category your product falls into in your market.
How we help
We check whether a supplier can steam-sterilise leafy herbs in their own plant or relies on an outside unit, and we test the packed lot at an NABL-accredited lab. You get the original reports before you release payment. Ask for a free sourcing review.