Walnuts are harvested to full maturation and must be peeled, washed, and bleached, but without the treatment affecting the core.
Drying is mandatory, up to 12% when stored as whole fruits and up to 8% if stored as core (peeled).
At harvest, the mesocarp must break out easily.
After peeling, they are then washed and dried in a hot air stream at 40-50 degrees Celsius. Nuts with good chalky welding bloom in calcium hypochlorite solution, crystallized sodium carbonate and water. Separately, a second solution of sulfuric acid and water (very diluted) is prepared. The two solutions mix in a ratio of 15/1. This mixture drips over the walnuts for 2-5 minutes.
Keeping nuts in the bark is done at a temperature of 0 to 3 degrees Celsius and at a relative humidity of 75%. The nuts are packed in sacks, pouches, or in a layer of 15-25 cm thick.
The core is stored in a 12-15 kg pouch at a temperature of 0 to 3 degrees Celsius and humidified 60-65%. Storage time should not be too high.