Rotten onion

You can pretty much find onions in all kitchens today since they are a great way to flavor food. However, they do spoil, and consuming a spoilt onion can be bad for your health. How to know an onion has gone bad? And, more importanly, can I still use it?

Generally, a bad onion would be soft and soggy when squeezed and may emit a foul smell. The surface may also be moldy, with green, white, or brown spots on the surface. It may also start sprouting.

This article will discuss the appearance and smell of a rotten onion, as well as other questions about bad onions, such as how long it takes to spoil and whether you can still eat parts of a spoiled onion. 

What Do Spoiled Onions Look Like

In general, spoiled onions tend to be soft and soggy to the touch and may have spots on the outer layer. These are molds and can be in green, black, or brown color. The spoiled onion may also emit a foul smell, usually hydrogen sulfide. 

When in doubt whether an onion has gone bad, always observe the onion and see if they show any signs as listed below:

  • Is there mold on the onion?
  • Does the onion have any discoloration? 
  • Is the onion smelling foul?
  • Is the onion soft or soggy?
  • Are there soft spots on the onion?
  • Has the onion started sprouting?

Suppose the onions show any of the signs above. In that case, you may consider discarding the onion completely or cutting out the spoiled parts and using the still ok ones. The latter may be risky but may be very helpful in emergencies or when you just need a bit of chopped onion for example.

How Long Does It Take For An Onion To Spoil

Onions may spoil as fast as a few weeks if kept in a warm, humid environment. If kept in cool, dry location, onions may last up to one to three months. Storing in the refrigerator may help the onion stay fresh longer, but it may absorb moisture and become soft. 

Like garlic, onions can stay fresh for a long time. If the storage is right, fresh whole onions can last anywhere from one to three months and sometimes even longer. How well you store them makes all the difference.

The best way to store onions and prevent them to go bad is keeping them in a cool, dry and dark place may help them last up to three months. This is because the onions do not absorb the moisture from the dry air. The cool air serves as a natural refrigerator, keeping bacteria from growing and spoiling the onion. 

Refrigerators may help the onion to last longer. Still, the results would be similar to keeping your onion in a cool, dry place. This is because the lower temperature in a fridge may suppress bacteria growth, the air inside a fridge may be humid, and the onions may absorb it. As a result, the onions turn soggy.

The fastest way to spoil onions is to keep them in a warm, humid place. Such an environment encourages bacterial growth, and the moist air is absorbed by the onion, causing it to spoil faster. 

Can you still use a bad onion? 

If an onion shows signs of spoilage such as mold growth, a slimy texture, a strong foul odor, or extensive decay, it is generally not safe to use. Consuming spoiled onions can pose a risk of foodborne illness.

However, if the onion has only minor soft spots and bruise, slight discoloration, or minimal sprouting, you can salvage it by removing the affected areas. Cut away any soft or moldy parts, ensuring that only the fresh and firm sections of the onion remain. Smell the onion after trimming to ensure it doesn’t have a foul odor.

Keep in mind that the quality and taste of the onion may be compromised even after trimming. It might certainly lose some of the sweetness for sure. If you’re uncertain about the condition of the onion or have any doubts about its safety, it’s best to err on the side of caution and discard it.

Do Onions Go Bad In The Fridge

Yes, onions do go bad in the fridge. Refrigerators help the onions stay fresh longer, but they do not preserve the onions long-term. Onions usually absorb the humid air inside the refrigerator and eventually become soft and spoiled within two to three months. 

Many vegetables may survive long when stored in a refrigerator. The same could be said about onions as well. Generally, they last two to three months in a fridge before spoiling. 

The low temperature inside the refrigerator may prohibit bacterial growth. Still, onions absorb the moist air inside the fridge and slowly become soft and soggy, to the point that these onions are no longer edible. 

I keep mine in the basement but if you don’t have one, a cellar, the garage or a pantry at room temperature can be as good. 

Therefore it is best to use up the onions before that happens. You can easily chop them up and put in a freezer bag or airtight containers to use when convenient. Onions are such a versatile ingredient and so many recipes use them!

Do Not Keep them in a plastic bag (unless to be frozen) since that is the perfect way to help them rotting very quickly for lack of ventilation.

What Happens If You Eat An Onion That Has Gone Bad

Eating rotten onions can result in conditions as mild as bad breath to dangerous health problems such as food poisoning. Spoiled onions may contain the salmonella bacteria that causes diarrhea, or hydrogen sulfide that causes bad breath.

At times you may be in a rush to cook a meal and notice that you have run out of fresh onions and are left with the spoiled ones. 

You then think about if you can just cook it since heat may kill all the nasty rotten stuff, right?

Hold back. Toss away those rotten onions, as they can still be bad for you. 

Spoilt onions may contain hydrogen sulfide. This compound usually appears when the sugars inside the onion are broken down by bacteria. They do not cause significant health problems, although they may leave you with bad breath.

Hydrogen sulfide is also the compound that causes a bad taste in your dishes when you use a bad onion. 

The biggest danger with spoiled onions is salmonella. Expired, spoiled food has a tendency to carry salmonella in it, and this bacteria is known to have caused thousands of food poisoning cases every year in the US. 

When poisoned with salmonella, you may experience stomach cramps and diarrhea. These symptoms may appear 24-72 hours after consuming the spoilt onion. 

Can You Cut Bad Parts Of An Onion that has gone bad?

Generally, removing the bad parts of the onion and eating the rest is safe, provided it is done correctly. The key is to ensure the remaining parts do not contain mold and soft, soggy parts. You may also wash the remaining parts to clean them. 

What happens when you need onions and only have a sprouted onion in your hands? Cut out the spoiled parts, and keep the ok ones for use. 

However, do understand that you are treading on the fine ground here. If you do not do this properly, you may have onion parts that still contain mold and bacteria. These nasties may either ruin the taste of your food or cause a rough time for your digestive system. 

Peel off any layers of onions that have brown spots or may have turned soft. Cut the onion at the center, and remove any inside parts that have gone soft as well. Cut the remaining onions into the shape you want, and give the whole cut-out a wash, to remove any residue mold. 

Can I plant onions that have sprouted in my pantry? 

Yes, you can plant onions that have sprouted in your pantry. In fact, sprouted onions can be used to grow new onion plants.

Start by choosing onions that have sprouted green shoots from the top. Find a suitable location in your garden or prepare a container with well-draining soil. Dig a small hole or trench and place the sprouted onion bulb in it, making sure the shoots are facing upward. 

Cover the bulb lightly with soil, leaving the shoots exposed. Water the plants regularly, ensuring the soil remains moist but not overly saturated. Provide adequate sunlight and weed the area around the onions. 

Over time, the sprouted onions will continue to grow and develop into new onion bulbs. Remember that onions grown from sprouted bulbs may have slightly different characteristics than those grown from seeds or sets. It can be a rewarding way to repurpose sprouted onions and grow your own fresh produce. 

What are some signs that your onion powder has gone bad?

Onion powder, like other spices, can lose its potency and flavor over time. While it doesn’t spoil in the same way as fresh produce, there are signs that indicate onion powder has gone bad or deteriorated. Here are some common signs to look for:

  1. Loss of aroma: Fresh onion powder has a strong, pungent aroma. If your onion powder has lost its characteristic smell or has a weak, dull scent, it may be an indication that it has gone bad.
  2. Changes in color or texture: Check for any discoloration in the powder. If the onion powder has turned darker or has developed clumps or lumps, it may have absorbed moisture, which can lead to spoilage or mold growth.
  3. Off taste: If your onion powder has an unusual or unpleasant taste, it may have degraded or become rancid. Taste a small amount to determine if it still possesses the desired flavor. If it tastes stale or has a bitter or rancid taste, it’s best to discard it.
  4. Excessive moisture: Moisture can cause onion powder to clump together or form hard chunks. If you notice any signs of moisture, such as caking or clumping, it’s an indication that the powder has absorbed moisture from the environment, which can compromise its quality.
Onion powder

To ensure the freshness and quality of your onion powder, it’s advisable to store it in an airtight container in a cool, dry place away from heat, moisture, and direct sunlight. 

Proper storage helps to maintain its flavor and prolong its shelf life.

What types of Onions are there?

There are several types of onions, each with its own flavor profile, appearance, and best culinary uses. 

Yellow onions 

These are the most widely used and readily available onions. They have a strong, pungent flavor and a slightly sweet taste when cooked. Yellow onions are versatile and can be used in a variety of dishes, including soups, stews, sauces, and caramelized onions.

White Onions

They have a milder and sweeter flavor compared to yellow ones. Their crisp texture makes them good to use raw in salads, salsas, and Mexican or Latin American cuisine.

Red onions 

These have a mild to moderate flavor and a vibrant purplish-red skin. They have a slightly sweet taste and are commonly used raw in salads, sandwiches, and pickled preparations. Their attractive color also makes them a popular choice for garnishing.

Sweet Onions

Such as Vidalia, Walla Walla, or Maui onions, have a high sugar content and a mild flavor. They are less pungent than other onion varieties and are known for their sweet and juicy taste. Sweet onions are excellent for eating raw in salads, sandwiches, or as a topping for burgers.


They are small onions with a more delicate flavor and a hint of garlic. They have a mild and slightly sweet taste and are often used in French and Asian cuisines. Shallots are great for sauces, dressings, and dishes where a subtle onion flavor is desired.

Spring Onions

Also known as scallions or green onions, are young onions harvested before the bulb fully develops. They have a milder flavor and are often used raw in salads, garnishes, or as a flavoring in various dishes.

These are just a few examples of the many onion varieties available. The choice of onion type depends on personal taste preferences and the specific culinary application.

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