Steam sterilisation treats spices or seeds with saturated steam to reduce total plate count, yeast and mould, and pathogens such as Salmonella. If it is done well, the loss of flavour and colour is limited.
You need it when your own customers or your market set microbiological limits that raw spice will not reliably meet. That is common for food manufacturers in the EU, the UK and the US, and for any product that will be eaten without further cooking.
Why raw spices carry microbes
Most spices are dried in the open, often on the ground or on farm floors, and handled many times before they reach a processor. Dust, soil, birds and insects all add microbial load. Cleaning removes dirt you can see. It does not remove bacteria.
For a product that goes into a curry that will be boiled, the risk is lower. For a seasoning sprinkled onto a snack, a ready meal or a sandwich, the spice may be the only step where a pathogen gets in. That is why buyers in those sectors ask for treated material.
How the process works
The basic steps are similar across plants, though the equipment and settings differ.
- Cleaned product is fed into a chamber or continuous system.
- Saturated steam is applied at a controlled temperature for a controlled time.
- The product is dried quickly to bring moisture back within spec.
- It is cooled and packed in a clean area so it is not contaminated again.
- Each batch is tested for microbiology after treatment.
Alternatives and what to avoid
Irradiation is another way to reduce microbes. It is restricted in the EU and irradiated food must be labelled there, so many European buyers do not accept it. Check your own market's rules before you agree to it.
Ethylene oxide (ETO) fumigation was once used on spices and sesame. It is not permitted on food in the EU and has caused large recalls. Read why EU buyers reject ETO treatment before you sign any contract. Your spec should say steam sterilised and "no ETO treatment" in plain words.
Questions to ask a supplier
Steam sterilisation is only as good as the plant and the controls around it. A badly run process can leave the product damp, darken its colour or drive off flavour. A good one with poor hygiene afterwards undoes its own work.
- Is the steriliser in your own plant, or do you send product to another unit?
- What microbiological limits can you guarantee after treatment, and on what basis?
- How do you keep treated product apart from untreated product?
- Which lab tests each batch, and will they send results to me directly?
- Can I see records from the last few batches of the same product?
Write it into the specification
Do not stop at "sterilised". State the method, the microbiological parameters you need and the test methods, and make the limits match your customer's requirements. Treated product should be tested after treatment, on a sample drawn by someone working for you. Our article on reading a lab certificate covers what to check on the result.
How we help
We identify processors that run steam sterilisation in their own plant, check the process and segregation on site, and have post-treatment samples tested at an NABL-accredited lab. Tell us your microbiological limits through a free sourcing review.