OK, I actually do not know this directly, but
remember it had to do with ions and hence did a
fast search yielding the following:
"The composition of the bowl in which you
beat egg whites can make a big difference. A
copper bowl reacts chemically with egg whites to
form fluffy, high-rise whites - it contains an
ion which reacts with an egg white protein,
specifically conalbumin, to form a more
stable foam and helps the whites retain moisture.
The same result can be obtained using
stainless steel or glass bowls with the addition
of cream of tartar. However, I don't use a glass
bowl because I have found that when using it, its
naturally slick surface doesn't give much traction
for the egg whites to climb the bowl.
Avoid plastic or wooden bowls because of
their naturally porous surface which attracts
grease because of its porous surface; grease or
fat deflates egg whites. Never use aluminum
which reacts with the egg whites causing them to
turn slightly gray."
In addition to the source where I took this
information, one could check in various books that
discuss the chemistry of cooking, by
Barham, P. 2002. The Science of
Cooking (Springer Verlag)
Coenders, A. 1992 . The chemistry of
cooking : an account of what happens to food
before, during, and after cooking. Parthenon Pub.
I've always wondered this too! One reason why
people use metal containers to whip cream is that
metal will stay cold when chilled, and it
is important when making whipped cream that you
beat the cream when it is cold and keep it cold
while beating it. Since the beating process
generates heat, whipping the cream in a cold metal
bowl can help counteract this buildup of heat.
What happens when you whip heavy cream with
lots of fat in it The fat forms a matrix
that traps air (tiny drops of fat disperse evenly
and stick together). This fat matrix falls
apart when warm.(Egg whites whip up the same
way not because of fat but protein, so they
remain somewhat solid at room temperature. Copper
bowls help the process of beating egg whites, but
this is a different story.) Cool Whip isn't real
whipped cream, so itdoesn't melt as easily.
You could probably mix whipped cream in a
glass or plastic bowl if you did so in a cold room
with cold beaters and cold cream. Adding a
little gelatin to stabilize the whipped cream
(make it more firm) might also help.
I was not able to find out anything about whip
cream and metal bowls. I do know that the
temperature at which you whip the cream is very
important. Some recipes call for refrigerating the
cream, bowl, and beaters before starting the
whipping. The reason for this is to make sure
the fat globules in the cream are as stiff as
possible - they hold a better foam that way.
I know that copper bowls are better than any
other kind for whipping egg white because the
copper ions form a complex with the egg white
proteins and help make them more stable. Perhaps
there is something similar that does on with
whipping cream and iron or zinc ions in a
stainless steel bowl.
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