Eggs 101, An introduction
There are a lot of differences between eggs but the ones that typically matter the least are the ones that you can see. So In this first installment I will deal with the size and color of eggs. Both size and color of eggs are based on the breed of chicken and the age of the hen. I will discuss them separately.
First let us deal with color. In general there are 3 shades of eggs: white, brown/tan and blue/green shades. So there are white layers like the Leghorn from Foghorn leghorn cartoon fame. There are brown egg layers like the Rhode Island Red or the Golden Buff that we currently raise and there are Blue/Green layers like the Ameraucana. There are hundreds of breeds of chickens but each breed only lays one shade of eggs. When we first started farming I had some Ameraucanas, Leghorns and Rhode Island Reds. It made for a very pretty egg basket or dozen of eggs with all the different colors and shades. But we kept having customers come up and ask for "brown eggs" , so I would have to run into the back room and start switching eggs in the package so that dozen had only brown eggs. That also meant some other customer would end up with just white or blue eggs. I would try to explain that the color of the egg shell didn't have anything to do with flavor or whether they were "farm" eggs. They just wanted the brown ones.
So how did a brown egg get synonymous with a healthy egg and a white egg with industrial production? Well it has to do with production, a hen eats whether she lays an egg or not. So hens that lay more eggs per year are more profitable than hens that that lay fewer eggs per year. One of the most prolific chicken breeds is the leghorn which lays a white egg. Well the big egg houses all bought and bred leghorns because they produced the most eggs therefore were more profitable. At the same time that old backyard farm hen was typically what we call a dual purpose breed. By dual purpose we meant they could be raised for eggs or meat (they were a little larger, heartier breed). Most dual purpose breeds lay brown eggs. So this meant that the barnyard chicken that was free to range all over the farm and yard eating grass, bugs, kitchen scraps, leftover animal feed laid a nicer eating egg than the industrial hen kept in a cage. The whole time the difference wasn't the color it was how they were raised. But the association between color and quality was made and still runs to this day even though it is not true. As soon as the big egg houses found out you would pay more for a brown egg than a white egg, they stated raising and breeding brown egg layers in same confinement houses that the white egg layers were in so they could control their costs and now you have a brown eggs everywhere.
Color is typically introduced into the shell of the egg at the end of the egg formation process. It takes a hen about 24 hours to make an egg. After the contents of the egg are formed she starts to put the shell around it. At the very end of the process in non-white eggs she will inject the shell with a dye to color the egg as a camouflage against predators that would eat the egg. You can tell this happens at the end of the egg formation process because most brown eggs have a white inside shell and a brown outside shell. Meaning the dye was injected right before it was laid. As a hen ages she will begin to run out of dye, so eggs she laid when she was younger will be darker than eggs she laid when when she is older. Sometimes you will see eggs with speckles on them this is just some excess dye that did not get a chance to complete disperse around the egg before it was laid.
Size, like color are dependent on breed and age of a hen. There are breeds of hens that lay large and extra-large eggs and breeds that lay medium and small eggs. Most hens that are kept for eggs lay a large egg when they reach maturity. Most chickens will start to lay when they reach the age of 18-22 weeks or 4-6 months old. A female chicken that has not started laying yet is called a pullet. When a pullet first starts to lay it lays a very small egg that will grow in size as she ages. So with most hens/pullets that are available for us farmers to buy it will take about a month for a pullet that just starts laying small eggs to become a hen laying large or extra large eggs. So from time to time when we start to replace our hens you will see one of 2 things. We might have pullet eggs for sale, these will just be a dozen of smaller eggs or you might buy a dozen eggs that have jumbo eggs and medium sized eggs in the same box. This will be some eggs from our old hens and some from our new hens just coming to age in the same package.
One of the reasons that we replace hens from time to time is that the younger a hen is the more frequently she will lay. A hen will lay 20% more eggs in her first year of lay than in her second. This will continue to decline as she ages so it is very difficult to keep hens profitably for much past 2 or 3 years old.
I hope this help you see that size and color are just functions of nature and not nutrition or taste. Both nutrition and taste I will deal with in another installment. Next week I want to discuss labels and definitions. We will talk the difference between cage-free, free-range, organic and all the other confusing terms we see on egg cartons in our stores.