Salmonella reaches onion from soil, irrigation water, birds, rodents, insects and people handling the crop. Belt drying removes water but is not designed to kill bacteria, so Salmonella present before drying can survive in the dry product for a long time.
It is controlled by preventing contamination in the field and plant, using a validated kill step where the buyer needs one, and testing finished lots. Testing alone cannot make a product safe.
Where contamination comes from
- Field: soil, manure, irrigation water and animals.
- Raw onion handling: heaps on open ground, dirty crates and trucks.
- Wash water: water that is not clean or is reused without treatment can spread bacteria.
- Plant: birds and rodents in drying or storage areas, poor drainage, and dust.
- After drying: dirty milling, sieving and packing equipment, or people moving from raw to finished areas.
Why dry onion is a concern
Salmonella does not grow in a properly dried product, but it can survive. Dehydrated onion is often added to foods that are not cooked again, such as dips, dressings, snack seasonings and sandwich fillings. A small number of bacteria can then reach the consumer.
That is why many importing countries and food manufacturers treat Salmonella in spices and dried vegetables as a serious issue. Positive results can lead to rejected shipments, border holds and recalls. Check the current rules in your market with your own food authority.
How good plants control it
- Clean, treated water for washing, with records of checks.
- Physical separation between raw onion areas and dried product areas.
- Bird proofing, pest control and drains that do not pool water.
- Hygiene rules for workers, including hand washing and clothing, enforced in practice.
- Cleaning schedules for mills, sieves and packing lines.
- A validated microbial reduction step, such as steam treatment, where the product needs it.
- Positive release: lots are held until test results are back.
Testing and what it can show
Specs usually require Salmonella to be absent in a stated sample weight, often 25 g, tested by a recognised method at an accredited lab. Because contamination is uneven, a negative result on a few samples does not prove the whole lot is clean. More samples give more confidence.
Test before shipment so a positive lot never leaves India. Our guide to checking total plate count and coliforms covers sampling, and steam sterilisation explains the most common kill step.
What to put in the contract
- Salmonella absent in the agreed sample weight, with the method named.
- Whether a kill step is required, and which one.
- The number of samples per lot and who takes them.
- Hold and release rules: no loading until results are received.
- What happens to a positive lot: rejection, with no blending into other lots.
How we help
We audit the hygiene controls that matter for Salmonella, from water to packing, and confirm whether a plant has its own steam treatment or uses an outside unit. Sealed samples go to an NABL-accredited lab before loading. Start with a free sourcing review.