We eat them all the time, but how much do you know about that little ball of deliciousness that comes wrapped in it’s own sturdy package?  You probably are aware that they are an excellent source of cheap protein, and you might know that they have not been shown to raise cholesterol, but what about the fun aspects of the egg, and the other cool sciency stuff?  Here are some interesting facts that you may, or may not know about the simple egg.


Shell Color

The shells come in many colors[2] ranging from a very dark brown (from the Marans hen) to a creamy white, and all shades of blue and green.  The color of the shell is determined by the breed of chicken, not the color of the hen.  Some of the color is in the shell, while sme breeds "spray" a color after the shell has formed.  You can see this sometimes as sprayed freckles on the shell. The nutritional value of an egg is determined by the diet of the hen, not the color of the shell.  If you pay more for the brown ones thinking they are better for you, think again – it’s just marketing.  Birds of other species can have some dramatically colored shells on their eggs.  The giant, dark-green ball you find in an emu's nest is so specatacularly colored that you might think it's something from a science fiction movie.

eggsCredit: JestMe


The size of an egg comes from several factors.[2][1]  Some breeds of hen lay larger ones, while those from bantams can be very small.  As a hen ages, she tends to lay larger eggs. The smallest ones from full size hens come from hens under a year old, while hens over three years old can produce eggs that are huge. Also, as a hen ages she tends to produce fewer and fewer eggs each year.  Generaly the size of the species indicates the relative size of the egg.  Quail make a tiny little thing the size of a piece of candy, and an ostrich produces something large enough to feed several people.


That white ropy thing that you see when you crack a fresh egg is called the chalaza[1].  There are actually two of them, one on either side of the yolk lengthwise, and they serve to anchor the yolk in the center of the albumen.  As the yolk moves around, the chalazae may twist and bunch, looking more like a wad of string than a thread.  The fresher an egg is, the more noticeable the chalazae will be. This is common to all species.


There are two sections of “white”, albumen,  in the egg.  The white surrounding the yolk is encased in a thin membrane and appears to have structure when a raw egg is cracked open.  The outer section looks watery.  Another measure of freshness is how firm the albumen is when you crack open a raw egg.  Older eggs will have a more watery white as the inner membrane breaks down and the two sections combine.  When making meringues or other recipes that need whipped whites, fresher eggs will make a much nicer result.  For something like egg nog, removing the chalazae will give you a much more palatable drink.  They are easy to see and removing them by hand, or pressing the albumen through a sieve works well.

broken eggCredit: http://www.stockfreeimages.com/


The yolk color comes from diet, as does nutritional makeup of the egg.  Free range hens that eat a variety of greens and bugs (yes, hens eat bugs) will have a rich orange yolk, while those fed strictly on commercial feed have pale yellow yolks.  Chicken ranchers have realized that a dark yellow color is perceived as a quality product, so many use additives in their chickens’ feed to darken the yolk.  The yolk from a fresh egg looks very firm and round when raw.  As the egg ages, the yolk tends to lose its firmness and flatten out.

Blood Spot

Although rarely seen anymore in the carton you get from the store, that little blood red spot that sometimes shows up is just that, a spot of blood.  It comes from a small rupture in the hen’s oviduct while she’s producing the yolk.  The yolk then travels down the oviduct and is wrapped in albumen (the white) and finally the shell.  The spot of blood remains trapped on the surface of the yolk.  It is completely harmless and easily removed by grabbing it with your fingers. It doesn't change the taste at all.  Mass screening techniques used by giant producers usually catch blood spots while the quality of the product is examined, and eggs with spots are sent to commercial facilities to be used in baking, or other products that don’t require visually perfect products.

Nutrition and taste

The nutritional composition of an egg is determined by the hen’s diet.  Strong tasting foods such as onions, garlic, or fish can leave a noticeable, possibly unpleasant taste in the egg.  People with food intolerances may prefer to eat their breakfast from a hen who has been kept on a limited diet. Someone with soy intolerance, for example, might choose to eat only eggs produced by hens on a soyfree diet. 

roosterCredit: http://www.stockfreeimages.com/


You do not need a rooster for your hen to produce eggs.  Many hobby farmers don’t have roosters because of zoning restrictions, or other reasons and their happy hens produce spend just as much time and energy laying eggs as a larger farmer with roosters.  Hens that are housed with roosters are likely to produced fertilized eggs that are perfectly safe to eat.  If you remove the eggs  promptly from the nest and cool them to room temperature, they will not develop and will not have an embryo.  They will still have a germinal disc, but it is perfectly fine to eat

I hope you found this both interesting and useful, and I invite you to look around your neighborhood farmers’ markets to find some locally produced eggs.  Compare the taste of farm fresh eggs to store bought and you may never want a grocery store egg again.