Ask A Scientist© Chemistry Archive

name        Thomas N.
status      other
age         40s

Question -  I have a fellow employee that likes to bring in prepared
foods for lunch and to share with fellow employees. Often, the fellow
employee brings in meatloaf cooked in a pyrex container covered with
aluminum. It's clear some of the aluminum is dissolved by the tomato
  puree or ketchup on top of the meatloaf.
q 1) Where does the aluminum go?
q 2) If it is absorbed into the sauce and meatloaf, is it poisonous?

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Thomas,

In general, there is little cause for alarm. Aluminum is not considered to be
very toxic. Are there actually holes in the foil where the acids have eaten it
away? Aluminum foil discolors easily when used as a cooking covering. In
truth, I would probably eat the meatloaf and enjoy the generosity of the
benefactor and camaraderie of the folks sharing the food.
I don't know the motivation for your question. Often such queries are prompted
by concerns regarding Alzheimer's disease (AD). You may be among those who are
concerned that AD patients were found to have unusual aluminum levels in their
brains. However this has not been an established cause-and-effect. Fear
prompts one to assume that aluminum caused the AD condition. Indeed, it could
be the other way around -- that those afflicted with Alzheimer's disease
simply accumulate aluminum in their tissue. Should this be if interest or
concern, consider the following website and the links one can derive from it.
------------
http://www.alzforum.org/members/about/board/wisniew/93145759.html

Here is a snippet from the abstract of one research paper on the possible
relationship between AD and aluminum.

Extensive studies of the pathology of AD and Al-induced encephalopathy by our
group and others indicate that Al does not cause Alzheimer's disease
neuropathology. However, under certain conditions, cognition can be affected
when Al enters the brain. Therefore, for individuals with renal failure or
undergoing dialysis or individuals with a damaged blood-brain barrier, the
intake of Al should be controlled.
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Regards,
ProfHoff
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Hot tomato sauce is sufficiently acidic to dissolve aluminum. Acidic foods
should not be cooked in aluminum pots/pans, nor should they be cooked or
stored in contact with aluminum foil.

I'm not sure the toxicity of aluminum has been firmly established. Simple
minded chemistry would suggest that it competes with other polyvalent
ions -- Ca++, Mg++, Fe+++, etc., in various biological processes.

I think I would pass on meatloaf containing tomato sauce cooked in aluminum
foil.

Vince Calder
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I am not sure exactly what is in tomato that does the job, but tomato is
famous for dissolving aluminum at cooking temperatures.  Probably it'a a
carboxylic acid;  lots of fruits contain carboxylic acids (acetic acid,
malic acid, citric acid, tartaric acid) that are good "chelators" for
metals.  That means that they can bond to the metal atom and keep it from
combining with anything else.  So, as you expect, the aluminum has dissolved
into the food.

As metals go, aluminum is not especially poisonous.  It's not arsenic or
lead, or even copper, by a long shot.  (Yes, copper is an esssential
mineral, but it's toxic above very low levels.)  However, aluminum does
appear to be in higher levels in the brains of people with Alzheimer's
disease than in the brains of people without.  There is some evidence that
aluminum can cause brain proteins to form Alzheimer's plaque-like structures
in the test tube, but it hasn't been demonstrated in living brains.  So, to
be on the safe side, I try to avoid eating much aluminum if I can help it.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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