To store or not to store?

The image shows onions with signs of superficial black mold (blacksmut), most likely caused by the fungus Aspergillus niger. This is not an internal infection, but a surface contamination that typically appears when:

• Onions are harvested with residual moisture,
• Temperatures are high and ventilation is poor,
• Storage lasts too long at temperatures above +25 °C.

❌ Can such onions be stored in a warehouse for long-term?

No, not in their current condition.
Here’s why:

🚫 Risks:

• The fungus will continue to develop, especially in warm and humid conditions.
• Loss of weight and marketable appearance.
• Cross-contamination of healthy bulbs is possible.
• Problems with export/sales, especially in regulated markets (EU, GCC, etc.).

✅ What you can do:

1. Sorting and rejection:
• Sort out onions with visible fungal spots.
• Onions with mild surface mold may be used after proper sanitation, if allowed by market standards.

2. Cleaning:
• Mechanically remove affected outer skins and spores.
• Sanitize using 1-2% vinegar solution or diluted hydrogen peroxide, followed by drying.

3. Storage conditions:
• Temperature: +0 to +4 °C - suppresses Aspergillus growth.
• Humidity: 65-70% - below 60% causes shrinkage, above 75% promotes mold.
• Ensure strong ventilation and drying before storage.
• Monitor regularly for signs of spoilage.

4. Packaging:
• Use mesh bags or perforated crates - avoid plastic.
• Do not pile onions higher than 1.5 meters if quality is uncertain.

💡 Alternative:

If the volume is large - consider partnership with processors who can use such onions for:
• Dehydration (dry onion),
• Oil or juice extraction,
• Animal feed or technical processing.

Summary:

Onions with surface black mold (Aspergillus) can be stored short-term with proper drying and cooling, but are not suitable for long-term storage without serious risk of loss and quality degradation. Best options are cleaning, processing, or quick sale.