Drying and Curing
Mould During Drying: What to Do
Short answer: If mould appears during drying, remove mouldy nuts at once, improve airflow, spread the layer thinner, and check remaining nuts closely. Do not wash mouldy kernels back into use, and do not store a batch that shows spreading mould.
How this plays out
When mould appears on the drying layer, act at once and in the right order: remove mouldy nuts immediately, improve airflow, spread the layer thinner, and check the remaining nuts closely. Do not wash mouldy kernels back into use, and do not store a batch that shows spreading mould in the hope that storage will fix it. Prompt removal protects the rest of the batch, and delay protects only the mould.
Key points for this step
- Take mouldy nuts out immediately.
- Improve airflow and thin the layer.
- Discard mouldy kernels, do not rescue them.
Acting at once in the right order
When mould appears on a drying layer, the order of response matters as much as speed. Remove mouldy nuts immediately, before spores spread to neighbours, then improve airflow around the remaining layer, then spread the layer thinner if it was crowded, and finally check every remaining nut closely for early signs. Doing those steps in that order stops the immediate spread first and then fixes the conditions that allowed mould to start. Reversing the order, such as improving airflow before removing mouldy nuts, leaves the source in place while conditions improve around it.
Why mouldy kernels are never rescued by washing
Washing a mouldy kernel may remove visible mould from the surface, but it cannot remove mould that has grown into the kernel or the toxins and off flavours that mould can leave behind. A washed kernel also re-enters the batch damp, which recreates the very condition that allowed mould in the first place. Discarding mouldy kernels feels wasteful in a small harvest, yet rescuing them risks both health and the remaining batch, since a rescued mouldy nut stored among sound nuts can spread contamination during storage.
Checking the rest of the batch after mould appears
Mould on one part of a tray is a warning about the whole tray, because spores travel on air currents and on hands during turning. After removing visibly mouldy nuts, inspect neighbours closely, smell the layer for mustiness, and sample test nuts from several spots to judge whether the batch as a whole is still sound. If mould reappears quickly after removal, or if many nuts show early signs, the batch conditions, such as dampness or crowding, need fixing before the batch can be trusted, and a heavily affected batch should be discarded rather than nursed.
Preventing the next outbreak from this one
Every mould outbreak teaches something about the drying setup, whether the layer was too deep, airflow too weak, the room too damp, or wet started nuts were piled briefly. Note which factor applied, adjust trays, spacing or room choice for the next batch, and clean trays thoroughly before reuse so spores do not carry over. Mould prevention is mostly a matter of fixing the condition that the outbreak revealed, and a batch that teaches that lesson has not been entirely wasted even when part of it is lost.
Frequently asked questions
Should I throw away the whole tray if I find one mouldy nut?
One mouldy nut does not automatically condemn the whole tray, provided it is removed at once, neighbours are checked closely, and no further mould appears. A tray with a single early mouldy nut and otherwise sound, dry neighbours can usually continue drying with improved airflow and thinner spreading. If mould keeps appearing, or if many neighbours show signs, discard the batch rather than risking storage of a contaminated harvest.
Can mould on the shell be harmless while mould on the kernel is serious?
Shell mould is still a serious warning, because it shows conditions favour mould growth and the kernel inside may already be affected even if it looks clean on cracking. Test crack a sample of shell mouldy nuts, smell and inspect the kernels, and discard any whose kernels show mould, softness or off smells. Shell mould alone does not prove kernel mould, but it never justifies storing the nut without checking.
Does mould during drying mean my drying room is unsuitable?
Not necessarily, since mould can appear in a good room when a layer is too deep, airflow is blocked, or nuts started very wet. Check those batch factors first before blaming the room, and try a thinner layer with better spacing in the same room. If mould recurs across several batches despite thin layers and good airflow, then the room itself, through dampness or still air, is the likely cause and a different space should be tried.
How do I clean trays after a mould outbreak?
Clean trays thoroughly with hot soapy water, rinse well, and dry them completely before reuse, since damp trays carry spores into the next batch. Mesh trays need attention to their weave, where fragments and spores lodge, and wooden trays need full drying because wood holds moisture. Clean trays are part of the response to mould, not an optional tidy up, because spores left on a tray can start the next outbreak.
What to do next
Prompt removal protects the rest of the batch.