This black mold belongs to the genus Aspergillus of fungi and is known as the Aspergillus black mold. If your fingers come in contact with it, a good washing with soap and water will do the trick. However, onions carrying this mold are often bruised or damaged even up to their very core, so to be safe, you should simply throw away those that are contaminated.
Aspergillus black mold in onions grows in warm climates such as the farms in the southern states. Farmers and quality inspectors rarely know about this type of mold growth as it is hidden between the onion’s skins, and sometimes there are no visible signs of damage from the outside. Although mold is known to proliferate in humid conditions, Aspergillus in onions have also been common in extremely hot desert-like places where onions are cultivated.
A. niger is less likely to cause human illnesses than other Aspergillus species, but it has been found to produce an illness known as aspergillosis when large amounts of its spores are inhaled. Some symptoms of aspergillosis are: cough, chest pains, fever, and difficulty in breathing.
Severe cases may involve shock, chills, delirium, coughing up of blood, and blood clots. It’s also possible that the mold finds its way into your other organs and destroy healthy cells there, causing breathing difficulties, liver failure, or kidney failure.
Where Aspergillus black mold originates
The mold can start its attack even as the bulbs are still in the fields. They can also multiply during storage and can start from a simple bruising of the bulb. This is why it is important to handle the bulbs carefully during harvesting and processing – to keep damage to a minimum.
Some people simply wash away the offensive Aspergillus Black Mold until the onion is seemingly clean when inspected. However, tiny spores left behind are too microscopic to be seen. If you know the health problems associated with the ingestion of black mold, you’ll never think twice about throwing contaminated onions away.
If you are cultivating your own onions, always store them in a warm and dry place for curing, such as on wire baskets on your kitchen counter or hanging from your durty kitchen ceiling, and in a cool but dry place when storing.
As a rule of thumb, the temperature where you would be storing your onions should be in the range of 32 up to 40 degrees Fahrenheit. Any warmer would cause spoilage, and any increase in humidity would just encourage the growth of Aspergillus black mold.
Farmers have tried several fungicides to control the growth of this mold on onions, but no particular fungicide has been found to be effective. And as there’s no surefire way to tell whether your onions are contaminated, you’ll just have to be risking this possibility for now.