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Egg Structure and Composition: What You Need to Know

Let’s enlighten you with a look on the facts about egg structure and composition

You probably haven’t thought much about what eggs are made and what they look like from a structural point of view. Let’s enlighten you with a look on the facts about egg structure and composition to give you a fresh perspective on this nutritional powerhouse.

Does the egg shell protect an egg from bacteria?

The answer is twofold. There are several natural barriers (shell, yolk membranes and white layers) that work to guard against bacteria getting into the egg to curb growth inside it. These shell membranes discourage bacteria thanks to something called lysozyme. In addition, the layers of white are alkaline in nature and contain certain nutrients that bacteria can’t benefit from. This forms a physical barrier that doesn’t allow for the easy transfer of bacteria to the egg yolk, which is rich in those nutrients that bacteria crave. Check out the following diagram:

egg structure

How does Salmonella infect eggs?

Eggs can get infected via fecal contamination either by the hen laying the egg or the surrounding dirt. That’s why processing plants wash eggs before they get to market. Bacteria can also come from an internal source, such as from the hen’s ovary or oviduct.

Which part of the egg hosts bacteria?

The egg yolk is usually the culprit, since, as said above, it contains nutrients bacteria need to thrive. That’s why you should never eat uncooked or raw eggs.

What’s the difference between white and brown eggs?

It all has to do with the breed of the chicken. It’s simple really: white hens lay white eggs while brown hens lay brown eggs.

How does the internal appearance of the egg relate to its safety?

Sometimes the way the eggs looks is related to its safety but not always. You’ll see what we mean by the following chart:

Appearance Cause
Blood spot (meat spot) Rupture of one or more small blood vessels in the yolk at egg formation
Cloudy egg white Egg is very fresh
Color of yolk Varies on the pigments found in the hen’s feed
Green ring on hard-cooked yolk Caused by sulfur and iron compounds reacting on the surface of the yolk, usually the result of overcooking
Off-color such as pink, green or iridescent egg white Spoilage due to Pseudomonas bacteria, which makes a greenish, fluorescent, water-soluble pigment in the egg white
Black or green spots inside the egg Results of bacterial or fungal contamination of the egg

How is a double yolk egg formed?

This happens when a chicken releases two yolks into the same shell, usually occurring in very young hens due to an immature reproductive system. They’re still safe to eat!

Does a blood spot indicate contamination?

No, these are usually caused by the rupture of a blood vessel in the yolk during formation. Electronic spotters typically weed these out at the factory level, but occasionally one gets through. Don’t worry…these too are safe to eat.

Hopefully you found this tutorial to be helpful. Now you can impress your friends with your knowledge of egg structure and composition!


By | 2016-10-19T10:29:51+00:00 July 20th, 2015|Egg Structure & Composition|0 Comments

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