Eggs are a basic ingredient in the foods of several cultures (and a basic ingredient of life!). Breakfast, lunch and dinner put this handy, accessible food into use in many different ways. They can be scrambled, fried, boiled, and baked as a feature, or mixed, dipped, and beaten to serve as a binder. The inspiration for this post came from explaining to my dad that olive oil shouldn't be used on the grill because of the high heat and low smoking point of the oil. I suggested that he should apply the seasonings straight to the salmon or try an egg-white dip to get heavier coatings to stick. He then asked, "well, isn't an egg dip less healthy?" And here we are.
There are 3 main parts to an egg: the shell, the white, and the yolk. The color of the shell varies based on the species of the animal that lays it. Chicken eggs are by far the most widely used and typically come in white, brown or pink. Nutritional value is the same regardless of the shell color. The white acts as a barrier to the yolk and is mostly water with a bit of protein in the make up. The amount of water and protein decreases over time creating an air pocket, but more on that later. Finally, the yolk contains the majority of the nutrients, good and questionable, found in an egg.
So, to answer my dad's question, egg whites have no adverse dietary effects whether used as a binding dip or as the main feature in an egg white omelet. However, the white offers very little nutritional value on its own.
Now for the yolk. If you are conscious of your cholesterol levels, you probably don't eat the yolk (this is where all of the cholesterol in the egg exists). However, consider the reasoning on
World's Healthiest Foods that blood cholesterol levels are affected most by saturated fats, not raw cholesterol found in foods. In addition, research shows that 1-2 eggs a day will not harm blood cholesterol levels or significantly increase heart attack risk; in fact, studies show that eggs can actually improve the LDL to HDL ratio.
Other benefits of eggs (all from
WHFoods):
Protein - the type found in eggs may help to prevent blood clots
Choline - benefits brain health and it's anti-inflammatory characteristics help to prevent heart disease, osteoporosis, cognitive decline and Alzheimer's, and type-2 diabetes (other sources of choline include soybeans, cod, chicken and salmon - with eggs and soybeans being the highest concentrations).
Aids in weight-loss
USDA egg grades, AA, A, and B are based upon the quality of the shell, the size of the air pocket in the more pointy end of the shell, and the quality of the white and yolk. From the
Agricultural Marketing Service:
AA Quality
The shell must be clean, unbroken, and practically normal. The air cell must not exceed 1/8 inch in depth, may show unlimited movement, and may be free or bubbly. The white must be clear and firm so that the yolk is only slightly defined when the egg is twirled before the candling light. The yolk must be practically free from apparent defects.
A Quality
The shell must be clean, unbroken, and practically normal. The air cell must not exceed 3/16 inch in depth, may show unlimited movement, and may be free or bubbly. The white must be clear and at least reasonably firm so that the yolk outline is only fairly well defined when the egg is twirled before the candling light. The yolk must be practically free from apparent defects.
B Quality
The shell must be unbroken, may be abnormal, and may have slightly stained areas. Moderately stained areas are permitted if they do not cover more than 1/32 of the shell surface if localized, or 1/16 of the shell surface if scattered. Eggs having shells with prominent stains or adhering dirt are not permitted. The air cell may be over 3/16 inch in depth, may show unlimited movement, and may be free or bubbly. The white may be weak and watery so that the yolk outline is plainly visible when the egg is twirled before the candling light. The yolk may appear dark, enlarged, and flattened, and may show clearly visible germ development but no blood due to such development. It may show other serious defects that do not render the egg inedible. Small blood spots or meat spots (aggregating not more than 1/8 inch in diameter) may be present.
Store eggs pointy end down in the refrigerator in a closed container so they will dry out slower and be less likely to take on the smells of nearby foods. Eggs should last 2-4 weeks in the fridge. To test the freshness, place in a bowl of water, if they float, then they are bad.
Tips for cooking: Use fresh, new eggs for frying, baking, or any case where you need to whip to peaks (meringue, souffle, etc.). The white will be more firm and will lend to easier flipping when frying and a stronger structure when baking or whipping. Older eggs are still good for boiling and scrambling as the more liquid structure will not have a negative effect on the outcome (but still make sure they are fresh eggs).
![By Ren West (http://flickr.com/photos/renwest/436827618) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons](http://upload.wikimedia.org/wikipedia/commons/e/e5/White_chicken_egg.jpg "White Egg")
