Rotten egg? What’s up with this huge, weird-looking yolk?

What you see: A raw egg in which the yolk has spread out. There are odd wispy things in the yolk.
What it is: An egg hosting a microbial blowout.
Eat or toss: Toss! Toss! Toss!

Here at EatOrToss we often write about the many defenses eggs have against invading microbes. There’s the shell, membrane, and the egg white’s bacteria-fighting chemistry. Then there are the rules farmers and stores follow and the safe handling and cooking that we try to practice in our kitchens. 

All these measures ensure that eggs can usually evade problematic invaders. 

But something went wrong here. 

Microorganisms with a rotten agenda were undeterred by the shell, membranes and egg white and managed to arrive at the nutrient treasure trove of the yolk. There, they munched on the rich yellow bundle of deliciousness and expelled their own byproducts. The yolk became thinner, more translucent and more globular, as weird little ribbons of something-or-other formed in its midst.

This egg would no longer taste right, nor would it behave normally if you tried to cook or bake with it. Not that you would. 

The top reason to immediately dump this egg is that it could be contaminated with a pathogen that could make you sick. 

From just looking at this image, Deana R. Jones, who researches eggs at the U.S. Department of Agriculture, easily concluded that microbes had laid a path of destruction. But what kind of microbe? Impossible to say by just looking.

It could have been bacteria whose only goal was egg destruction (not human invasion), in which case, well, that’s gross, but not a health risk. 

But it’s entirely possible that this egg was hosting a pathogen, like salmonella, that could sicken a person. 

The Centers for Disease Control and Prevention estimates that every year in the United States, 1.35 million people are sickened and 420 die from infections from non-typhoidal salmonella (the type most common in the U.S.). Just shy of 7 percent of salmonella outbreaks were traced to eggs in 2018, according to the U.S. government’s most recent outbreak analysis. 

Given that risk, Jones advised dumping the egg and thoroughly cleaning and disinfecting the skillet and doing the same for whatever you use to clean the skillet (which might mean throwing away a sponge you use to clean it). 

Not all rotten eggs look the same

If you want to know what a rotten egg can look like, check out the image at the top of this post. But keep in mind that there are lots of ways for bacteria to mess with an egg and they all can look different. Without lab analysis, we can’t diagnose exactly what type of microbe destroyed this egg.

“When an egg is impacted by extensive microbial growth, the appearance is impacted by the organism(s) present,” Jones wrote in an email. “Therefore, there is not a ‘typical’ description of such a circumstance.”

This egg, for example, didn’t smell. But plenty of other bacterial invaders could generate an odor. 

And to further cover our bases, an egg could be contaminated with disease-causing bacteria and still look fine. That’s why it’s always important to cook them thoroughly.

What circumstances made this egg go bad?

It’s impossible to say what went wrong here, though it’s likely that both too much time and too-warm temperatures conspired to allow microbes to grow.

Perhaps, on the farm, this egg was laid in a strange place and sat out longer than is safe before a farmer collected it. Perhaps, temperature management wasn’t ideal when it was delivered to my doorstep in a cardboard box with a cold pack. Perhaps it sat in my fridge for too long before my husband cracked it open and then called out, “Hey, um, look at this….”

It could be a combination of the factors above or none of them at all, Jones told me. But the bottom line is: This is one bad egg. Toss!