Why Do Some Eggs Have Two Yolks?

Why Do Some Eggs Have Two Yolks?

Posted on: July 12th 2019

It’s Saturday morning. You’ve rolled out of bed after an extra hour of sleep and, now, it’s time for breakfast. You can already smell the bacon sizzling on the stove and the coffee perking in the coffeemaker. What better accompaniment for your bacon and coffee than a healthy helping of scrambled eggs? You crack the first egg and, much to your surprise, two yolks slide out of the shell and into the bowl.

You might have also wondered what are the odds of getting a double yolk egg? Eggs with two yolks, also known as “double yolkers,” are a rare phenomenon that occurs in roughly one out of every 1,000 eggs.

When it comes to double-yolk eggs, there’s good news and there’s bad news.

Because double yolks are rare, they’re the frequent subject of myths and superstitions. They’re also subject to more intense scrutiny, with many people wondering whether or not they’re safe to eat. The good news is, when you see those twin yolks floating around in a bowl, you don’t have to throw them away. Double-yolk eggs are perfectly safe to eat, although they likely won’t add any extra nutrition to your meal. The bad news is that they probably won’t do much to improve your luck, so you might want to hang on to that rabbit’s foot or four-leaf clover a little bit longer.

If they are safe to eat and don’t bring good luck, what’s so special about a double yolk?

Why Do Double Yolks Happen?

A double yolk occurs when a hen’s body releases more than one egg during her daily ovulation cycle. And, just like humans, it’s possible for two — or more — eggs to make their way from the ovary and through the reproductive tract.

The overall odds of a hen laying a double yolk are one in 1,000. What does that mean? It means that the odds of discovering an egg with a double yolk are about the same as the odds of catching a foul ball at a baseball game. In other words, it’s not impossible, but it isn’t a daily occurrence, either.

How Many Yolks Can An Egg Have At Once?

People have discovered eggs with three or four yolks, although those odds are even slimmer than those of a double yolk. The world record for the most yolks inside one eggshell is NINE. That’s right — nine yolks inside one eggshell. Now those must have been some pretty tasty scrambled eggs!

To understand how a double yolk situation occurs, let’s start by breaking down the mechanics.

Double Yolks Explained

Female chickens — hens — are born with two ovaries, just like humans. As the chick matures into an adult hen, her right ovary shrivels up, leaving her left ovary to handle the task of producing and releasing eggs. When we refer to the eggs that come from a hen’s ovaries, we aren’t talking about the shell and whites. We’re only talking about the round yellow part we know as “yolks.” The other stuff — what we know as a complete egg — comes later in the process.

A human female releases one egg approximately once a month, but a full-grown hen releases one yolk every 25 to 27 hours, or roughly once each day. Once the yolk leaves her ovary, it travels down her tube-shaped reproductive tract — the fallopian tube — collecting the additional materials that comprise an egg.

What Are The Materials of An Egg?

Well, first, the yolk collects the substance that comprises the egg white, called the “albumen.” The albumen surrounds the yolk and encapsulates it as it continues down the tube. Then, just before the hen releases the egg, the hen’s body adds the shell material to protect the yolk and the whites. Once all these layers are in place, the hen releases the egg. Voila! Breakfast is served!

The craziest part of it all is that the hen’s body will begin the process all over again within an hour — sometimes even less than that. A healthy hen will release a new yolk 30 to 70 minutes after laying her egg, and the new egg’s journey to existence will start all over again.

A Hen’s Reproductive Process

When it works as it should, the whole process is pretty simple. A hen’s body produces a yolk that gathers other stuff and becomes the thing we dye at Easter and include in brownies, cakes, and stir-fry, among other dishes. But, just like the human body, a hen’s body doesn’t always work the way it’s supposed to.

Since we can’t put a camera inside a hen to observe the reproduction process she goes through each day, it’s impossible to completely understand what happens to cause a double egg. However, as best as scientists can tell, a double yolk occurs when something interferes with the rhythm of a hen’s reproductive system. In other words, something causes her reproductive process to speed up and release two yolks rather than one. While they aren’t necessarily released simultaneously, the yolks get released close enough together that they end up traveling through the fallopian tube together. That means they end up getting bound together into the whites and, ultimately, the eggshell.

So which chickens lay double yolk eggs? Typically, double-yolk eggs are the most common among immature egg-laying hens, known as pullets. A pullet has started laying eggs, but her reproductive system is still maturing, which means a glitch, such as a double yolk, is more likely to occur. In young hens, the odds of producing a double-yolk egg are one in 1,000, which makes it a much more common occurrence than the overall statistics would indicate. And, if you have several pullets laying in the same house, then the odds of these eggs ending up together in egg cartons are even higher. That is why some people have found several double-yolk eggs in the same carton.

While it’s less common, double yolks can also happen in an older hen whose system is beginning to slow down and isn’t regulating itself the way it should. And, age aside, it’s also possible among certain heavier breeds of hen, such as the Buff Orpington, which hails from England, but is also a popular choice among American farmers today.

In other words, a double yolk isn’t “supposed” to happen, but it’s also not a sign something’s wrong. As a pullet matures and her body regulates itself, she will stop laying double-yolk eggs. As an older hen stops laying eggs, her body will no longer produce double- or single-yolk varieties.

People often ask us if double-yolk eggs can become twin chicks. While it’s fun to imagine a fuzzy little pair of twin chicks running around together, the truth is that double-yolk eggs aren’t good for breeding. They rarely yield chicks, even when fertilized. And, in cases where two chicks form, one often doesn’t survive because the embryos essentially compete with each other and the stronger of the two survives. In many of these cases, neither of the chicks live to hatch.

Double-Yolk Superstitions

You’ve probably heard you shouldn’t let a black cat cross your path, walking under ladders is risky, and breaking mirrors will guarantee that you’ll have bad luck for seven years to come. Superstitions of all kinds find their way into society over time. Even when they prove to be untrue, their pervasiveness among certain groups keeps these beliefs alive and well. Think we’re eggsaggerating? Did you walk down a sidewalk this morning and carefully step around any cracks that had formed?

While some superstitions like the black cat or cracks in the sidewalk are more commonly known, there are other, more obscure beliefs as well.

Double-yolk egg symbolism may not be as culturally universal as other superstitions, but these culinary anecdotes have found their place in the myths and belief systems of several cultures. Superstitions help us explain things that seem to have no explanation, giving us a reason for things that don’t make sense.

While the details of the superstitions vary among cultures — as do most things like this — most of the time, a double-yolk egg is supposedly a harbinger of one of three things.

1. Death

Ironically, eggs are usually a symbol of new life, but Norsemen believed double-yolk eggs were a sign death was preparing to come for a visit. In their culture, if you cracked an egg and discovered a double yolk, it meant someone in your family was going to die. It’s sobering indeed to be in the middle of preparing a meal, only to discover a double-yolk warning death, but this seems to be the only culture to have held this peculiar superstition.

2. Good Fortune

It turns out the ancient Norsemen’s beliefs about eggs and death haven’t carried over to other people and cultures. In the Wiccan belief system, a double yolk is a herald of good fortune for whoever cracks the egg. We could all use a little more luck, right? Bring on the double yolks!

3. Fertility

In some cultures, a double yolk is a sign a pregnancy is going to occur and, in many cases, people believe it heralds double joy by hinting twins are on the way — tempting if you’re trying to get pregnant. But, before you start cracking a dozen eggs looking for a double yolk, you might want to slow down. The superstition isn’t unique to the one who breaks the egg. So, even if you come across one, it just means someone you know will be experiencing a pregnancy soon. How’s that for a fun, but incredibly vague, superstition?

Even without a specific superstition in mind, people get worked up when they discover double yolks in their eggs, especially if they find two or more of these in the same carton. While we’d like to think a carton full of double-yolked eggs means 12 times the good fortune — or 12 times the children, if that’s your thing — 12 eggs with double yolks only indicates your eggs came from a farm that has a lot of young chickens laying eggs at the same time.

If you purchase eggs from a supermarket in the United States, it is very unlikely this phenomenon will never happen. But, if you buy your eggs from a private seller or somewhere outside the U.S. where the regulations are different, it’s not unheard of to find several double yolks in the same group of eggs.

Are Double-Yolk Eggs Healthy?

Now that we’ve dealt with the myths surrounding double-yolk eggs, let’s talk facts.

Eggs have had their fair share of good and bad publicity in recent years. For a while they were healthy, then there was some talk that they were bad for your cholesterol, and now, with the rise of diets like the keto diet, they’re back in the public’s good graces. Yes, egg yolks do impact your body’s cholesterol. However, eating them doesn’t harm your body’s blood cholesterol. Besides their essential nutrients, eggs — including the yolk — modify your body’s LDL cholesterol and lower your risk of heart disease.

Now that we’ve debunked the myth that egg yolks aren’t healthy, let’s look at what nutrients they bring to the table.

Egg yolks contain significant amounts of vitamins, including B-12 and vitamin D. They provide lutein and zeaxanthin, which help keep your eyes healthy, as well as fat. Eggs are also a healthy source of protein, but you can only realize their full benefits if you eat the yolk, which contains 40% of the protein in each egg.

Given these health benefits, it’s easy to assume a double-yolk egg would equal double the nutrients, right?

Not quite.

In a double-yolk egg, the two yolks inside the shell are smaller than the average yolk. That means each of the yolks may contain fewer nutrients. So, when you combine the two egg yolks, they will most likely mimic the nutritional content of one egg. If you’re looking for the numbers, the best way to measure the nutritional value of a double-yolk egg is to look at an extra-large egg’s nutrition facts. Ultimately, a double-yolk egg’s nutrition facts are comparable to a jumbo egg.

Even though a double yolk isn’t going to make much of a difference in your calorie count, it can potentially throw off a recipe because the ratio of egg yolk to egg white is different when there are two yolks involved. It probably won’t make a big difference if you’re whipping up scrambled eggs or a tasty omelet, but a double yolk can spell trouble in baking because it skews the recipe’s ratio of fat to sugar.

So what should you do if you’re baking a batch of chocolate chip cookies and a double-yolk egg falls into your bowl? Nothing. In most cases, as long as you’re using the entire egg in the recipe, the difference in the yolks isn’t going to skew the outcome of the dish. If your recipe calls for yolks only, you may need to adjust the number of eggs you’re separating and count the double yolks as two separate eggs.

Where Can I Get Double-Yolk Eggs?

Since a double yolk usually comes from a young chicken, it’s possible to find more than one in the same dozen. Why? Because that batch of eggs most likely came from the same supplier!

In most cases, one or two double-yolk eggs in a dozen are an anomaly that slipped through into a batch of “regular” eggs. But, did you know some countries consider double-yolk eggs to be a specialty food item? In the United Kingdom, high-end specialty food stores sell double-yolk eggs. But you probably won’t find this trend replicated on a large scale in the United States, except in Pennsylvania Dutch country!

Cartons of these unique eggs are sometimes available to buy locally, and Sauder’s even introduced them to a broader market, selling dozens of these eggs to a Brooklyn-based high-end food store called Gourmanoff. What took these eggs from anomaly to specialty item? Ultimately, the inspection process involved in double-yolk eggs is what set these eggs apart from the rest.

Sauder’s double-yolk eggs are hand-candled. Candling is the inspection process eggs go through before they get packaged and sent to stores for purchase. When an egg is hand-candled, it means an inspector looks for blood in the egg, cracks or fissures that might cause the egg white to leak from the egg. This process ensures quality eggs get delivered from the farmer to your kitchen every time.

Why is the idea of selling double-yolk eggs by the dozen so appealing? Besides the fact that it’s unique, egg yolks are one of the primary ingredients in hollandaise sauce, a delightful dressing that’s the trademark flavor of eggs Benedict, but also pairs well with asparagus, salmon, and broccoli. If you’re cooking hollandaise, custard, or any other food item that has egg yolks as a base, it’s nice to have two yolks in one.

Sauder’s and Double-Yolk Eggs

Our hens still produce these delightful culinary surprises. Even if you don’t buy a special package of double yolkers or believe that a double yolk symbolizes good luck or the approach of a new baby, it’s still fun to crack an egg and see those two bright yellow orbs sliding into your bowl.

Although many people consider them to be an imperfection, a double-yolk egg isn’t going to hurt you if you come across one. The color and flavor are the same as any other egg and, in most cases, it won’t change the taste or texture of your dish. Of course, there is one exception — baking. In some cases, a double-yolk egg may throw off a recipe because it could skew the fat-to-sugar ratio. However, this is rare and shouldn’t be cause for concern.

Sauder’s Eggs started in the 1930s as a family-owned business in the heart of Pennsylvania. Today, we still live by our family values, but our family is a little bit bigger now, with five egg facilities in three different states. In spite of our growth, our commitment to high-quality eggs has never wavered. What makes our eggs special is that they typically travel from farm to retailer within one day. Our farmers and their families gather the eggs in the morning for our trucks to pick up and, after a quick stop at our processing facilities, they go to our retailers for your table.

While we love a good egg breakfast, there’s so much more you can do with eggs besides scrambling them. They’re great fried, hard-boiled, poached — now we’re getting hungry! And, even if you aren’t a fan of eggs themselves, we think you’ll agree they are an essential base for many of the tastiest foods out there, including custard, mayonnaise, cookies, and more. Need some inspiration for egg-straordinary meals? Sauder’s recipes are a must-try for any at-home chef. Check out our online recipe collection for inspiration.

In the market for high-quality, farm-fresh eggs? Use the Sauder’s store locator to find a retailer near you!