You prevent condensation and mould by putting dry seed into a dry, sound container and limiting the moisture that can move around inside it. That means checking the seed, the bags, the container and the weather at loading, then adding lining and desiccants.
Most mould found on arrival started with moisture that was already in the container when the doors closed. The voyage only moved it around.
How container rain happens
A closed container is a sealed box of air and cargo. In the day the steel walls heat up and the air takes up moisture from the seed. At night, or in cooler waters, the walls cool and that moisture condenses on the roof and walls. It then drips back onto the top bags. Shippers call this container rain or container sweat.
Oilseeds are especially sensitive. Wet patches on sesame, peanuts or cottonseed can grow mould within days, and peanuts can develop aflatoxin.
Before loading
- Test seed moisture on the day, against the limit in your spec.
- Let freshly processed or freshly dried seed cool to ambient temperature before bagging.
- Use clean, dry bags, and do not store them on bare concrete.
- Inspect the container: no holes, no rust patches letting in light, sound door seals, and a dry, clean, odour-free floor.
- Reject containers that have carried chemicals or that smell of previous cargo.
- Avoid loading in rain. During the monsoon, roughly June to September, load under cover.
Inside the container
- Line the walls and floor with kraft paper or similar material to absorb drips and protect bags from steel.
- Hang desiccant bags or strips, in the quantity your supplier recommends for the route and season.
- Cover the top layer of bags with paper or a breathable sheet.
- Leave a small gap at the roof so air can move.
- Use only dry pallets if you palletise. Wet timber releases a lot of moisture.
- Close the doors quickly once loading is finished, and seal the container.
Route and timing
Long voyages that cross climate zones, such as India to northern Europe in winter, carry a higher risk of condensation. Ask the shipping line about ventilated containers for sensitive cargo, although these are not always available. Leaving containers in direct sun at transhipment ports also adds risk.
At destination, open the container promptly and unload in dry conditions. A container left closed in a yard for weeks after arrival can still develop mould.
Record everything
Photos of the empty container, the lining, the desiccants, the seal and the closed doors are your evidence if there is a claim. So is a moisture result on a sealed loading sample. Insurers and shippers will ask for these. Wider loading points are covered in common quality complaints with Indian oilseeds and safe moisture levels for shipping oilseeds.
How we help
We supervise loading in person: we check the container, the seed moisture, the lining and the desiccants, and we photograph each step. If a claim arises, you have a dated record to support it. Ask for a free sourcing review.