All eggs are edible. Even those of snakes or turtles and amphibians. But we will not find those here. Gulls eggs seem to be a delicacy. Quail eggs are also sought after. The shells are in principle also edible. An egg of an ostrich can weigh up to two kilograms. The smallest egg is that of the hummingbird. It weighs only 0.5 grams.
It is said that even fish eggs are edible...

If an egg is fertilized one will not remark by view, color or taste, as long as it is not incubated for several days. It is perfectly edible, and you do not know if  the egg you eat is or is not fertilized.

A hen with a white earlobe lays white eggs, brown eggs gives a dark earlobe. There is no impact on the taste! The (only) Belgian manufacturer of boiled eggs claims that brown are easier to peel than white (because they would have a less tough skin).

Egg yolks can have a different color due to other foods and become paler or redder (eg by pepper). Ducks that eat acorns would even have green yolks.

Keuringsdienst van Waarde found in September 2018 a difference between white and brown eggs.
Brown is more associated with 'free-range and healthy'. White chickens, however, need less food to produce the same egg, and go into the laying industry for several months longer as an egg machine. They are therefore 'more sustainable', with qualitatively the same eggs.

The shell is formed in about 14 hours, is about 0.3 mm thick, and porous with 10,000 holes trough which oxygen, carbon dioxide and water are let out of the egg. About 4% of the scale is protein, 95% is calcium carbonate.
The yolk is 1 cell, yellow to orange, depending on the used food. It is the largest known cell in nature. The chalaza (spiral strings) keeps the yolk in the middle of the egg. The yolk contains (18%) more protein than the aqueous protein (10%).

The shelf-life
The shelf life of a raw egg is four weeks from the date of laying. Keep it cool, dark, dry. It can easily at least twice as long, but of course no one will ’recommend’ this.
It is best to keep the tip down, so the egg yolk remains the best at its place and the air pocket remains above. Otherwise, the air rises up and makes the fleece loose.
The shell is naturally waxed, and feels a bit greasy. The shell itself is very porous. The membrane that is inside is a kind bio filter that blocks microorganisms. This combination of natural repellents works well. A ‘dirty’ egg can be kept longer than a clean egg. Brush or wipe the eggs with a dry cloth. Avoid moisture to keep the waxy cuticle intact. The shell is porous, so if you make it wet, bacteria can penetrate the egg easier and spoil it.
In the refrigerator the drying process is faster but the bacteriological process slower. The natural enzymes that are in the egg eat the albumin proteins (a bit). The membranes of the protein dissolve (partly). The egg yolk will sink down and eventually break down in the egg. It is not looking nice as you break open an egg like this. It flows as an omelet out from the shell. As long as the content does not stink like ’rotten eggs’ there is very little to worry about. Regularly turning the egg around prevents that the yolk touches the shell and decay occurs.

The shell you can break on the edge of a pan, or by splitting it with a knife. Then you break both halves open. To separate yolk and egg white for preparations quietly let run the white from the shell in a cup. The rest you can pour carefully several times from one cap into the other. This will keep the yolk in the shell.

Youcanbreakeggsina bowl, and then with a PET bottleaspipette, vacuum the yolk(s).
Every baker who experienced the war, will wipe the empty shells with his thumbs as bowl scrapers to back out the last bit of protein. If you leave the caps some time you see how much protein and string still is in it.
Let the shells dry thoroughly. Then you can easily crumble and give them back to the chickens. Pure recycling.

Use only very fresh eggs for raw preparations like mayonnaise, mousses, Bavarian cream…

Checking freshness
eiversWhile developing an air chamber a membrane grows between the outer and the inner shell. Which increases as the egg gets older.

  • If you put a fresh egg in a glass of water (with salt), then it will sink to the bottom. An egg that is no longer fresh, rises to the surface by the larger air chamber.
  • Break the egg on a flat plate: a fresh egg yolk is nice round, neatly in the middle of the white.
  • In a fresh egg, the protein is firmly. Shake your egg gently back and forth to your ear, you hear almost nothing. Do the same with an older egg, you hear the moving content.
  • The egg is not fresh when you hear beeping a chick.

Distribution delivers eggs in small (43 and 53 gram), medium (63) and large (-73).
By spinning an egg around you can test if it is cooked or raw. A hardboiled egg will spin around rapidly, the content is fixed. A raw egg wobbles.

Eggs and salmonella
Salmonella are various bacteria from the natural flora of many animals.
With special action, the egg sector reduced the rates of infection of eggs to virtually zero (0.3%).
Preventive each user should apply all rules of hygiene, and use common sense. Best you cannot use raw eggs in dishes. Use them fried or boiled.
Contamination is mainly found on the shell, so let the contents of the egg not come into contact with the shell. Do not use a half eggshell decorative on raw tartar (bad habit).

With a shortage of lime a wind-egg is shaped, which does have a membrane, but no shell. You can dry empty shells and return them crumbled to your chickens.
The concept of free-range eggs and free-range chickens is somewhat misleading. The animals live somewhat better than a chicken in battery cages with 9 instead of 18.2 per m2. They live (?) in maximum 3 floors, with minimum 1/3th floor surface without grid, and with litter.
The bills may be cut or burned. Nutrition is not regulated. They are not free range chickens, and certainly no organic chickens.

Patience is a beautiful thing, but it has never helps a cock lay an egg. (John W. Raper)