[Sca-cooks] **OOP** Hard Cooking Eggs

[Avraham haRofeh]

> > Yes, I *do* use the cold water bath when boiling... but the cold water
bath
> > is used here, and it doesn't work, either...
>
> I didn't mean to imply that you didn't. I'm sorry if there was offense
> taken. The fact that I'm not getting green rings no matter how long I boil
> the eggs puzzles me-- clearly the reasoning of the green ring=overcooked
> is contradicted by your experience:
>
> Wierd. Maybe we should ask some kitchen chemists if they have any ideas.

According to Shirley Corriher, in _CookWise_, "It is accepted that the ugly
green layer on the yolk is the result of iron in the yolk combining with
sulfur (hydrogen sulfide) in the white to form green iron sulfide. Author
Harold McGee recently did some experiments in which he got the yolks green
all the way through, indicating that the yolk alone contains enough iron and
sulfur to produce the green iron sulfide. While the egg is cooking, heat
speeds up this chemical reaction. The longer the egg cooks, the greater the
chance for discoloration, so watch the time carefully. Quick cooling also
helps prevent the layer from forming."

McGee himself says in _On Food and Cooking_, "The other oddity about
hard-boiled eggs is the occasional appearance of a greenish-gray
discoloration on the surface of the yolk. The color is caused by a harmless
compound of iron and sulfur called ferrous sulfide, which is formed only
when the egg is heated, especially in the case of an extra-alkaline
less-than-fresh egg. The yolk contains a good deal of iron, and the albumen
a good deal of sulfur, primarily on side chains in the protein ovalbumin.
When that protein is heated, some of its sulfur atoms are liberated and
react with hydrogen ions in the albumen to form hydrogen sulfide (H2S). In
minute quantities this gas lends a characteristic and pleasant odor to
cooked eggs and meat, but in larger quantities is the odor we associate with
rotten eggs. As the gas forms, it diffuses in all directions, and some
reaches the surface of the yolk, where it encounters iron and reacts to form
the dark particles of ferrous sulfide (FeS). The way to minimize the
discoloration is to minimize the amount of hydrogen sulfide that reaches the
yolk. First, cook the eggs only as long as is necessary to set the yolk.
Then plunge the cooked eggs immediately into cold water. This lowers the
pressure of the gas in the outer regions of the white, since cool gases
exert less pressure than hot, and cool protein loses less sulfur than hot.
Consequently the hydrogen sulfide diffuses away from the yolk, toward the
region of lower pressure at the surface. Finally, peel the eggs promptly:
this also helps pull the gas away from the yolk."

Avraham

****************************************
Avraham haRofeh of Northpass
     (mka Randy Goldberg MD)
RandomTag: They also serve who only stand and wait.