I have never heard of this before so I did a Google search and found the article below. Hope this helps.

Dave

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Don't Got Foiled

Suzanne Ezell of Atlanta put flank steak and marinade in a metal baking pan and covered it with aluminum foil. "When I checked on the meat, I discovered holes in the foil," Suzanne writes. "I contacted the Reynolds Kitchens, and they explained what happened."

They replied: "...In rare occurrences, aluminum foil may react with the food that is being covered and form small pinholes in the foil. This does not affect the safety of the food.

"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 reaction we recommend that aluminum, glass, ceramic, plastic, or paper items be used with foil rather than stainless steel, iron, sterling silver, or silver-plated pieces.

"If the reaction occurred while using an aluminum, glass, ceramic, plastic, or paper container, the reaction was chemical. This reaction may occur when salt, vinegar, highly acidic foods or highly spiced foods come in contact with aluminum foil.

"The product of either of these reactions is a harmless aluminum salt that can be safely consumed."