If you love to cook onions, you might be wondering why onions turn blue after cooking. This is a common question because many people automatically assume something has gone wrong when their onions turn blue.
Especially since most foods don’t change color until they start spoiling. So you might automatically think that this is a bad sign and you shouldn’t eat those onions.
But there are actually many cases where products may change color depending on the situation. Be it the temperature, the environment or the type of vegetable that has changed colour.
So there may be other reasons if a vegetable you cooked changed color after you put it in the fridge. Read on to find out why onions turned blue and if they’re still safe to eat in hindsight.
Why have my onions turned blue?
If you cook red onions and they turn blue, you might be wondering why that happened. Red onions often turn a blue tint after cooking and storing in the refrigerator due to an alkaline reaction of the onions.
This is actually a fairly common reaction that purple products have after cooking. So you can actually notice this with other purple produce like red cabbage as it often turns blue too.
You can assume this means your red onions went bad before you could eat them. However, this is a normal process and nothing to worry about as the red onions are still safe to eat.
They simply had a chemical reaction once cooked and stored away, causing the purple color to turn blue. It can be a bright blue, a light blue, or even a bluish-green color.
In any case, this doesn’t mean the onions have gone bad or are unsafe to eat. As long as they haven’t been in the fridge for long, they are still fresh and safe to eat.
They may just not look as pretty, which is why some people prefer to cook their red onions as they eat them. Instead of storing them in the fridge where they can discolour.
You can eat an onion that has turned green
If you have an onion that has started to turn green, you may be concerned and think it is unsafe to eat. But the good news is that this is most likely nothing to worry about and you can still eat that onion.
White onions and yellow onions, in particular, can begin to take on a greenish tint when exposed to sunlight. This has a chemical reaction and can produce a green color on a perfectly healthy onion.
You can even slice an onion if some of the layers inside are greenish in color. This isn’t usually a concern either, unless they’re very soft or slimy, which would indicate they’ve gone bad.
So color changes in onions are not uncommon and usually don’t mean the onion has gone bad.
Is it normal for onions to discolour?
You might worry about your onions if they start to change color. Many people may think this indicates that they have gone bad or are no longer edible.
But discoloration can also indicate a variety of things, not necessarily that the onion has gone bad. So it’s helpful to understand why onions can be discolored so you don’t throw them away when they’re still perfectly edible.
bruises
Many onions change color if they’ve been bruised in transit or after you’ve brought them home. This is especially true for thin-skinned onions, as they don’t have as much protection.
You’ll notice bruising if certain spots on the onion are much darker than the rest of the onion. In white or yellow onions, this often looks light tan or brown, while red onions have much darker spots.
These discolored areas can be cut off and the rest of the onion used as usual.
Chemical reaction
Onions are very susceptible to chemical reactions depending on the environment and the temperature they have been exposed to. Because of this, red onions cannot turn blue if they are cooked and then placed in a cold environment such as a refrigerator.
Red onions also turn a much lighter and redder shade of purple when cooked with an acid. So if you cooked red onions with vinegar or lemon juice, they would take on a much more vibrant appearance as a chemical reaction.
light reaction
Onions can also react to light, as excessive sunlight can cause a white or yellow onion to turn green. This indicates that these parts of the onion have started to form chlorophyll and are responding to the sunlight.
You can still eat the onion, and you can even eat the green part if you want, as there’s nothing wrong with that.
Finally
If you cooked red onions and they turned blue, it’s still safe to eat them as it was just a chemical reaction. Chemical reactions are very common with onions, and you may even find your red onions come alive in some cases.
It is even normal for onions to turn green or have brown spots depending on the situation.
