Cooking For Engineers

[gue0]

The egg being fat and protein and (minus the shell), is over 90% water. The shell is porous and leaches water into the atmosphere. As an egg ages the membrane between the shell and the white looses moisture and shrinks. This shrinkage causes the shell to lose its porosity and become a seal if sorts. This process will take place over a varying length of time depending on the storage method employed. The longer the shell remains moisturized, the slower the process of sealing off the contents of the shell to the outside world. Theoretically then, eggs stored in a water bath should not dry out at all. In boiling eggs, the membrane shrinks around the egg further and will appear to bond with the white given the white has lost enough water to separate it from the membrane. Eggs nearing this stage will be easier to peel if done so under a trickle of cold running water.
Temperature to start with is important for two reasons, one being by starting refrigerated eggs in cold water alllows them to heat up at relatively the same rate as the water and thus the shell is less likely to crack and raising the temperature slowly further insures a an even expansion. Second, as an egg ages the shell looses porosity due to shrinkage and pressurization due to heat will cause breakage. In old eggs you will note that bubbles will air vent while boiling and this is due to the shell having shrunk so far as that the pores have proceeded to expand thus venting excess pressure. These eggs will not peel unless run under cold water while they are still hot, however an old egg will be rubbery in texture compared to a fresh one even though is is otherwise unspoiled.
So with this to go on, dehydration wouid seem to be the biggest enemy.
Next is spoilage. When a bird lays an egg the egg has a waxy coating to prevent both the transpiration of water and the admission of bacteria from entering the shell. When eggs are washed, there goes the protection. Handling between laying and the carton you buy them in is where the largest chance of contamination occurs. Unwashed farm fresh eggs will keep longer than those washed prior to marketing. Bacterial growth in eggs already contaminated is not generally harmful in that its growth is in its infancy and retarded by refrigeration.
I am tiring of this, so in an eggshell, eggs that bleed air while boiling will not peel cleanly. old eggs can be revitalized by mixing water to them e.g. scrambling, warming the eggs prior to cooking will make for a fluffier omlette and frying them at lower temperatures will keep evaporation to a minimum and tenderness at a maximum.

[Loriann2000]

If you are lucky enough to live in a city where you can get farm fresh eggs - I'm just up the highway from you in Salem, OR, so you can drive up here if you can't find them down there. They come with the coating from the chicken still left on without being rinsed off. There are 2 farms up here that offer eggs direct from their chickens that haven't been rinsed. Unfortunately, one of the farms got closed due to a health department issue, but the other one is still operating. Reply if you want the location. This coating prevents any air from getting into the egg and you can actually store them on your counter-top without refrigeration for about a week. The lack of refrigeration means that the proteins aren't stressed and your genoise cake or mousse is incredibly rich.

[gue0]

Alton Brown must have been here, (yeah, right) as I saw a show of his on cooking the egg only two weeks after my post. ....m(°¿°)m..... His main point was equally valid in that whatever you do with the egg, don't over cook it unless you are making a prop for a movie set or a play. Whether its scrambled, fried, baked, poached, or a custard, it will continue to cook after its removed from the heat. Fluffy and tender is all about water content, so keep it in. Maybe someone would like to discuss the separated egg and its possibilities, eg. mayonaise and meringue?