Aspergillus black mold on onions: what should be done with them?
This black mold belongs to the Aspergillus genus of fungi and is known as Aspergillus black mold. If your fingers come into contact with it, a good wash with soap and water will suffice. However, onions that carry this mold are often bruised or damaged even down to the center, so to be safe, you should simply throw away the contaminated ones.
Aspergillus black mold on onions grows in hot climates, such as farms in southern states. Farmers and quality inspectors are rarely aware of this type of mold growth as it is hidden between the onion skin and sometimes there are no visible signs of damage from the outside. Although mold is known to thrive in humid conditions, Aspergillus on onions has also been common in extremely hot desert locations where onions are grown.
A. niger is less likely to cause human disease than other Aspergillus species, but it has been found to cause a disease known as aspergillosis when large amounts of its spores are inhaled. Some symptoms of aspergillosis are: cough, chest pains, fever, and shortness of breath.
Severe cases can include shock, chills, delirium, coughing up blood, and blood clots. It’s also possible for mold to find its way to your other organs and destroy healthy cells there, causing shortness of breath, liver failure, or kidney failure.
Where does Aspergillus black mold originate?
Mold can begin its attack even when the bulbs are still in the field. They can also multiply during storage and can start with a simple bruise on the bulb. This is why it is important to handle the bulbs with care during harvesting and processing, to keep damage to a minimum.
Some people simply wash off the offending Aspergillus black mold until the onion is apparently clean when inspected. However, the tiny spores that remain are too microscopic to be seen. If you know the health problems associated with ingesting black mold, you will never think twice about throwing out contaminated onions.
If you are growing your own onions, always store them in a warm, dry place for curing, such as in wire baskets on your kitchen counter or hanging from your dirty kitchen ceiling, and in a cool but dry place when storing.
As a general rule of thumb, the temperature where you would store the onions should be in the range of 32 to 40 degrees Fahrenheit. Any heating would cause deterioration, and any increase in humidity would only stimulate the growth of Aspergillus black mold.
Farmers have tried various fungicides to control the growth of this mold on onions, but no particular fungicide has been found to be effective. And since there is no sure way to tell if your onions are contaminated, you will only have to risk this possibility for now.