How to Detect a Rotten Onion: A Simple Guide

Onions are an essential ingredient in various culinary dishes globally. It is challenging to prepare any food without including onions in it. Moreover, onions are great additives when cooking soups and stews. However, it is crucial to know when an onion is rotten since it can hugely impact a recipe’s overall taste. In this article, we will discuss everything you need to know about onions’ freshness and how to detect a rotten onion.

Understanding the Different Types of Onions

Before we delve into the most practical ways to tell if an onion is rotten, we have to understand the different types of onions. Knowing the types of onions can significantly affect how you detect rottenness in onions.

Yellow Onions

Yellow onions are the most widely used type of onion in most dishes. They have a pungent flavor and are moderately juicy. Yellow onions have a yellow-brownish skin and white flesh.

White Onions

White onions have a milder taste than yellow onions. They have off-white skin and white flesh. They are suitable for salads, salsas, and Mexican cuisine.

Red Onions

Red onions are commonly used in salads and sandwiches. They have a slightly sweet and tangy taste, and their color varies from bright red to purple depending on the type of red onion.

  • When is an onion bad?
    • An onion is bad when it smells bad, looks moldy or sprouts.

How to Tell if an Onion is Rotten

When an onion goes bad, it can affect the quality of food it has been added to. Below are the ways to tell if an onion is rotten:

Sprouted Onion

If your onion has a green sprout, then it may not be rotten, but it is not fresh either. Sprouted onions are way past their ripe stage and have lost some of their quality taste. On the other hand, an onion with a sprout that looks dry and feels mushy is a sign the onion is rotten.

Moldy Onion

A moldy onion will have black mold spots or white fuzzy areas. When you notice any signs of mold, it’s time to discard the onion immediately. Mold in onions can cause harm to one’s health when ingested.

Soft and Light Onion

An onion’s texture can also help determine if it is rotten. When you notice that the onion feels squishy, soft, or even light, it is a clear sign that it is no longer good for consumption. This happens because moisture has entered the onion, causing it to rot from the inside out.

Off Smell

Onions should emit a distinct onion smell. However, when an onion has gone bad, it gives off an unpleasant odor. If you notice that your onion smells sour, rotten or moldy, then it is no longer safe for consumption.

Discolored Onion

Another sign that an onion is no longer good for consumption is discoloration. When onions start to spoil, they lose their distinct color and start to go yellow, causing them to become mushy and moldy. A yellow onion has a higher chance of rotting faster than white onions since yellow onions have a higher sulfur content.

Storage Tips to Keep Your Onions Fresh

To avoid buying a rotten onion, you need to know how to store onions correctly. Storing onions correctly is crucial to keep them fresh and flavorful for longer.

Room Temperature Storage

You can store onions at room temperature in a well-ventilated room. They will last for several weeks when stored this way. However, avoid storing them near a heat source or in direct sunlight since this can cause them to start sprouting or rotting.

Fridge Storage

Another way to store onions is to place them in the fridge. Ensure to wrap each onion in a paper towel, plus you need to make sure that your fridge is clean since any bad odors from other foods can get absorbed by the onions, thus affecting the quality of other stored foods.

Freezer Storage

When you do not plan to use onions soon, you can store them in the freezer. All you need to do is chop onions into small pieces before placing them in a sealable freezer bag. Doing this will make it easy to use the onions anytime you need them.


The onset of a rotten onion can ruin any dish that it’s added to, and it’s critical to know how to detect a rotten onion to avoid this. When checking if an onion is rotten, it’s best to use all of the methods mentioned above. Also, you should always store your onions properly, away from heat and moisture, to keep them fresh and flavorful for more extended periods.


  • Can I still use a yellow onion that has gone soft?
    • No, onions that feel soft and squishy are a sign of rotting and should be discarded immediately.
  • Can I smell an onion to know if it’s rotten?
    • Yes, when onions have gone bad, they emit an unmistakable sour, musty aroma.
  • Can I still consume onions with a little mold?
    • No, mold on onions is harmful to our health when ingested and should be discarded.
  • Is it safe to store onions in the fridge?
    • Yes, storing onions in the fridge is a great way to prevent them from spoiling quickly.



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