Cooking For Engineers

[Duane]

As you probably know, apple can be quite acidic, especially when it's concentrated.

Well, I just finished cooking apple butter in a relatively new Calphalon One Infused Anodized pot. The butter cooked over a low heat for several days.

Afterward, I realized that the inside anodized surface had gone away. Now it's all bright silvery aluminum-colored below the level of the apple butter. The bright aluminum also feels slightly pitted like an old, raw aluminum pot.

I'm wondering if de-anodizing dumps chemicals into the food, or does it just change the surface of the metal? Do I need to throw away all of that apple butter? You can't imagine how much work it was to peel all those apples and stir and cook for so many days, but I don't want to ingest a bunch of aluminum or other chemicals.

[opqdan]

The anodized coating is simply a coating of aluminum oxide on the pan (the pan is the anode, thus the name).

The aluminum oxide layer should be non-reactive and quite hard. From my Calphalon literature, I gather that baring some sort of laboratory experiment, no amount of acidic food is going to remove that coating. The anodized coating is put on in a sulphuric acid bath, so I doubt apple butter would have any effect on it.

If your anodized layer was removed, something went wrong in the process, and you should contact the manufacturer for a replacement.

I don't know anything about the health risks of Al oxide, but if it seems like it would be inert, especially to be used on cookware, although I doubt it is good for you. I would, once again, consult the manufacturer.

[GaryProtein]

Aluminum oxide is sapphire. It is essentially inert in the body and is completely safe. In the past, certain types of implants have been made of single crystal and fused crystaline aluminum oxide/sapphire.

The sub-surface of a damaged anodized aluminum pan, when in a reactive cooking environment may not be so safe. Also, the anodized surface of Calphalon pans happens to be easy to damage. Yes, I know that when you rub a smooth blunt metal utensil on the anodize, the metal rubs off onto the anodize, and it may LOOK like the anodize is cut through even though it isn't, but with a sharper instrument against the anodized pan, as when you might stir something with a fork, the subsurface aluminum is soft enough to NOT support the brittle anodize on the surface, and it does come off or become cut.

[Duane]

Thanks, opqdan and GaryProtein. I appreciate the responses.

opqdan writes: "no amount of acidic food is going to remove that coating. The anodized coating is put on in a sulphuric acid bath, so I doubt apple butter would have any effect on it."

Well, put your doubts aside. The anodized surface is gone. All that is left is a pitted, rough, and raw aluminum substrate. Importantly, the anodization only disappeared at and below the exact level of the apple butter. Also, I stirred it with a wooden spoon, so forget about rub-off.

Keep in mind that apple butter cooks for several days at a very low temperature, and concentrated apple can be very acidic.

I called Calphalon. The rep admitted that they have seen this before and that it was definitely covered under warranty. She told me to return the pot and it would be replaced, no questions asked. While I'm grateful for her help, I'm also miffed. All of their product literature makes it sound like nothing short of an act of God can remove their anodized coating, yet this rep knew better.

[Duane]

Re: Aluminum Oxide

I did a little research on my own, and discovered some interesting facts. It turns out that all metal pots give off some metal into your food. (Of course, this seems a bit obvious to me in retrospect.) Cast iron is soft and releases a lot of iron into food, but the added mineral is good for most people. Aluminum, especially older aluminum, is also quite soft and reactive. One source claimed that aluminum pots release between 45 and 200 micrograms per serving.

(See more here: http://www.hc-sc.gc.ca/iyh-vsv/prod/cook-cuisinier_e.html)

Not to worry, as this study (PDF file) indicates: "Dietary intake of aluminum, estimated to be in the 0.10–0.12 mg Al/kg/day range in adults (Pennington and Schoen 1995), has not been of historical concern with regard to toxicity due to its presence in food and the generally recognized as safe (GRAS) status of aluminum-containing food additives by the FDA. Users of aluminum-containing medications that are healthy (i.e., have normal kidney function) can ingest much larger amounts of aluminum than in the diet, possibly as high as 12–71 mg Al/kg/day from antacid/antiulcer products and 2–10 mg Al/kg/day from buffered analgesics when taken at recommended dosages (Lione 1985b). "

It seems that since aluminum is one of the most common elements in nature, the body has learned to handle relatively large quantities of it quite well.

I have decided that the aluminum in my food is probably higher than average, perhaps even quite high. If I ate the apple butter in large quantities, then I'd probably be doing some damage. However, since I only ever eat about a teaspoon or two with an occasional meal, my overall consumption is probably low. Besides, taking antacids or other medication would put way, way more aluminum in my body.

By the way, stainless steel appears to be the least reactive metal. I plan to buy a stainless steel kettle for making acidic food like apple butter and tomato sauce in the future. Live and learn.

[opqdan]

Thanks for the info about the metals. Did the Calphalon rep say anything about what causes it? I imagine that this doesn't normally happen and was due to a deffect in manufacturing.

[melon]

Isn't the cause for concern about ingesting aluminum based on the research that shows Alzheimers patients having high quantities of aluminum in their brains? As soon as that information came out, it seems as though everyone would stop buying aluminum pots.

Obviously the material of the pot will come out in the food. I, for one, don't need any more aluminum than that which can't be avoided. I will return my Calphalon pan.

[Guest]

There is a difference between aluminum oxide and alumina oxide. Manufacturers usually say they use alumina on their products because this is not poisoning. Aluminum is highly dangerous if ingested for longer periods. Aluminum is an essential nutrients, but in our society there seems to be a much greater chance of getting too much aluminum rather than too little. Here are some common sources of aluminum that you need to avoid if your hair test shows high aluminum: antiperspirants and underarm deodorants, aluminum cookware (especially dangerous if acid foods like tomatoes are cooked), beverages from aluminum cans, municipal drinking water which often has aluminum compounds added, baking powders, bleached flour, processed cheese, some table salts, some antacids, and breathing in dust when sanding with aluminum oxide sandpaper.

[Kencook]

I had a similar experience with a well used Calphalon stock pot. The company rep said my pot had "silvered out", had me ship it back and sent me a brand new one, no charge.

[GaryProtein]

[Guest]

You mentioned that the sub metal beneath anodizing or non-stick may be more dangerous. Could you expand on that. Aren't old aluminum pots and pans basically raw aluminum? I am evaluating a non-anodized aluminum system for new cooking product and trying to understand the "safety" of 6063 extruded aluminum and if anodizing is worth the added cost.

Thanks,

[David]

It is not that hard to remove the aluminum anodizing in the pot. Running them through the dishwasher is usually enough - many dishwasher detergents are caustic (base) enough to remove the anodizing. I would suspect your apple butter was basic and not acidic, perhaps one of the ingredients that went in early was basic if not the fruit themselves. Lye is commonly used to strip anodizing.

I would be concerned about eating that food. The anodizing itself is alumina - aluminum oxide, as has been said above, however, if you have removed it and are left with a shiny aluminum surface, you have succesfully reduced the coating back to metallic aluminum (plain Al), which may or may not be bad for you in large quantities - removing all the anodizing on a pot and dumping it into one meal is far more aluminum than what has been studies based on the normal slow leaching of aluminum from pots/pans.

The biggest thing I would be worried about is the dye used to color the anodizing. The anodized layer itself is porous and clear - if you want that characterisitic dark gray Calphalon color, a dye has to be added to the anodized coating after it is initially coated and before it is sealed. I don't know what dye Calphalon uses, but I looked online and could not find any anodizing dye that was labeled as "food grade". Calphalon may make their own dye - who knows?? Anodizing has been grandfathered in by the US FDA since it has been in use for so long, but no specific dyes are listed or discussed as acceptable.

[Guest]

Guest here.
I had almost the exact same thing happen with the older Calphalon Anodized series saucepan (2 1/2 qt) (the flat stock handles on pans and lids, not the cast curvy profile handles, which are a later series)

Again, the food was apple-based. In this case mulled apple cider, where you simmer the cider with spices for about 3 hours.
Presto, when I poured the cider, the inside of the pot was birght silver from the "waterline" all the way to the bottom.

Interesting to know this happened to someone else. These pans are REALLY expensive!!! Imagine that jazz...you boil apples and it destroys it? What the heck? Although more expensive and probably better-engineered pans are now on the market, this is really pretty astonishing.

I'll contact a local Calphalon rep and see what happens. We're about to throw it away due to concern over aluminum and long-term risk of alsheimers disease.

[blackdogchef]

Update: Called Calphalon customer service and they are sending a replacement no questions aksed (after I ship them my old one)

Seem's good to me...still curious as to why this happend siwht apples and not tomatoes.

[Gary]

Wow, I was so excited reading about how great the Calphalon Everyday 12" pan with lid was, I ordered one. When it arrived I had all kinds of dishes waiting to be made.
My first dish was a simple braising of chicken with rice with a dash of lemon juice. It cooked great, clean up easy but to my great disappointment and shock there was a silver patina inside the pan up to where the food had been. I followed all the instructions that came with the pan and read them thouroughly for anything that might explain this phenominon inside my "everyday" pan.
After Googling for about an hour with keywordw: Calphalon silver, I discovered something Calphalon hadn't mentioned in theire literature: Deanondization.
I called the rep there and she sent me a form to send my pan back in for replacement. That's fine, but now I can cook ANYTHING acidic like pasta sauce, chili..etc. Those are everyday foods to me. I'm very disappointed and can see I will have to treat this expensive pan like a baby. Gary