Aluminum and the Bain Marie

[phatch]

When I make cheesecake, I wrap my springform pan in aluminum foil to keep the water out of the cheesecake (mostly the crust, really). It works well, but there are side effects.

The pan most practical for me to use as the water bath is an aluminum 1/2 jelly roll pan. The inside of this pan turns black every time I do this, except where the springform pan is. I've done it without the aluminum foil wrap and the jelly pan doesn't discolor then. The black fades away to dark alumnumn after a few times through the dish washer, but still persists.

Both pan and foil are aluminum, I wouldn't think I'd get the current discharge between two disparate metals but that's all I can think of. The springform is steel with a glass bottom, but the discoloration doesn't happen with just the springform in the bain marie.

What to do to prevent this discoloration?

Phil

[Suzanne]

I don't know the exact science behind it (although I suppose I could look it up in Harold McGee or Shirley Corriher), but yes, I believe it IS just an electro-chemical reaction between the foil and the aluminum jelly roll pan. Maybe the water (moisture) acts as a transfer medium, since the discoloration affects the entire jelly roll pan.

Similar instance: when you cover the leftovers in an aluminum take-out container with foil, you come back the next day to pinholes in the foil and little disgusting gray spots on the surface of the food. Same reaction, I think.

The glass and stainless steel of the springform are non-reactive -- they will not react chemically with other substances. That's not the case with anything aluminum, which is why it's bad to have acid ingredients in aluminum containers.

[kokopuffs]

I think that we're talking Al + H2O ==> Aluminum Oxide (black color).

[Bryan Blinstrup]

the black spots on food are due to the acid content of the food. There is a reaction between the acid adn the aluminum that causes a breakdown in the aluminum. The black is the residual material from the breakdown.

An esy solution: Plastic wrap, then foil

(And please to meet you all, as this is my first post)

[miahoyhoy]

Well Hi there!

thanks for the 411.

[phatch]

From the Reynold's Aluminum Foil FAQ

http://www.reynoldskitchens.com/reyn...s_wrap/faq.asp


Why does the Reynolds Wrap® Aluminum Foil carton say to "cover bowls
and platters except stainless steel or silver trays with foil"?
Occasionally when aluminum foil comes in contact with a different
metal or a food that is highly salted or acidic, small pinholes are
formed in the foil. This is a harmless reaction that does not affect
the safety of the food. It is difficult to predict, but may occur
under the following conditions:

1. When aluminum and a dissimilar metal are in contact in the presence
of moisture, an electrolytic reaction may occur causing a breakdown of
the aluminum. To avoid this use aluminum, glass, ceramic, plastic or
paper containers. Do not cover sterling silver, silverplate, stainless
steel or iron utensils with aluminum foil.

2. A similar reaction may occur when salt, vinegar, highly acidic
foods or highly spiced foods come in contact with aluminum foil. The
result of these reactions is a harmless aluminum salt. Some aluminum
salts are used in medicines to treat stomach disorders. The food can
be safely eaten; however, the aluminum salt particles can be removed
from the food to improve the appearance of the food.

[Bryan Blinstrup]

Well, this thread might have seemed a little random. I wanted to reply to "Aluminum and the Bain Marie,"but I clicked on the wrong button. If any moderators read this, can you please move this thread into "Aluminum adn the Bain Marie."

Thanks,
Bryan

Your wish is my command (at least on this board! ) -- Suzanne