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Aluminum pans and acidic foods

I have read that you should avoid cooking or marinating acidic foods in aluminum cookware because the acids will react with the aluminum, causing the metal to leach into the food and the cookware to become discolored and/or pitted.

Is there any risk of this if I use an aluminum half sheet pan as a prep tray to hold food that has already been marinated in citrus juices? Realistically the food would probably be sitting on the pan for no more than a half hour before I would take it off and grill it. It could be another few hours before I would actually get around to washing the pan. Similarly, would there be any risk of leaching if I put citrus marinated foods onto an aluminum pan right after grilling it?

Sorry if these are dumb questions, but I'm a beginner and I'd rather not ruin my food and/or cookware if at all possible.

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  1. You will be fine. I believe that heat has something to do with it. Tomato sauce, for example, can pick up a metallic taste when cooking in aliminum, yet it may be packed in an aluminum can.

    1. <I have read that you should avoid cooking or marinating acidic foods in aluminum cookware because the acids will react with the aluminum, causing the metal to leach into the food and the cookware to become discolored and/or pitted. >

      This is true for the most parts.

      <Is there any risk of this if I use an aluminum half sheet pan as a prep tray to hold food that has already been marinated in citrus juices?>

      It really depends what you mean by "risk". Your pan may get discolor a little bit, but no one will get sick.

      2 Replies
      1. re: Chemicalkinetics

        Will the aluminum affect the taste of the food?

        1. re: Citizen_Snips

          Some people say it does, but I am not sensitive enough to taste the difference. I am also the kind of person who barely taste the iron from a cast iron cookware. I can taste a little, but it never bothers me, whereas it is a much bigger turn off for others.

      2. Hi, C_S:

        Actually these are not dumb questions. They need to be asked and re-asked from time to time, so that the terms 'common' and 'knowledge' stay in their proper places.

        I have eaten acidic foods prepared in unanodized aluminum cookware now for 54 years, right alongside the same foods cooked in pans of different materials. I can't say I have ever detected any metallic taste, pitting or cookware ruination (several of my aluminum pans have been in the family longer than I have, and are generally better-liked), but I *have* noticed some *food* discoloration. The classic example is that onions and eggs may turn greyish in bare aluminum, but this has more to do with sulphur compounds than acids. If you scour your aluminum clean before each use, you can expect this to happen more. If you let it age gracefully, less. Let me ask *you*: Have you ever icked out over metallic taste of leftovers that were put away wrapped in foil?

        In the case of your half sheet pan, you should be fine. No aluminum sheet will look pristine for long (if it does, you need to cook more). If you're the least bit hesitant, that's why the Good Lord made parchment paper.

        Relax and enjoy your shrimp.

        Aloha,
        Kaleo

        1. Just this week I marinated a spatchcocked chicken in lemon juice, rosemary, garlic and olive oil on an aluminum quarter-sheet pan. I had never given a thought to the idea that it might be a health risk to me (and, throwing caution to the wind, will continue to use and love my aluminum cookware). Even with a 24-hour marination, there was no effect on the aluminum sheet pan. You'll be fine.

          1. I used my aluminum half sheet pans for the first time last night. One pan was used to hold the raw food before I grilled it (pork chops with a dry spice rub and asparagus marinated in a red wine vinaigrette), and the other pan was used to hold the cooked food as it came off the grill.

            Unfortunately the pan that was used to hold the cooked food developed discolored splotches where the food had been resting. I guess I could understand the asparagus leaving marks on the pan since it contained vinegar, but the pork chops seem puzzling to me since they only had dry spices on them.

            I cleaned the pan by hand with dish soap and a nylon brush and later with a blue 3M sponge, but the discolored splotches were not affected. The sponge and towel I used to wash and dry the pan picked up a lot of gray and black residue, however. I then tried using some bon ami on the blue sponge. I was able to get rid of the splotches, but then I was left with light swirl marks from the bon ami powder.

            I did some searching on here and it seems the black residue I was wiping off was aluminum oxide. Is that correct? Is it still safe to use the pan, or should I throw it out and get another one? The other threads I read seemed to suggest it was still safe, but not everyone agreed on that.

            I had no idea aluminum cookware could be this finicky. Maybe I'll get some SS half sheet pans to use as prep/serving trays for my outdoor grilling. At least I know they won't react with anything.

            14 Replies
            1. re: Citizen_Snips

              Hi, C_S:

              Yes, what you got when you scoured was Aluminum Oxide. What you need to know is that aluminum is remarkably corrosion-resistant because of a natural process called *passivation* (which also protects SS). When aluminum is exposed to air and the elements, it quickly forms a very thin layer of aluminum oxide, which protects the reactive substrate from corrosion. When you scour that layer away, corrosion occurs again until another passivation layer forms (or if you've left some swarf). If you're totally OCD about it, the alternating scouring and corrosion can wear through thin double-wall pans.

              On the other hand, if you just relax, you get a nice luminous silver-grey surface that becomes less reactive. I have a few 1950s aluminum meat platters that now look like pewter, and steaks with salty rubs and acid marinades on them have no further effect.

              But your pans are quite safe to use--your problem is cosmetic. The splotches will merge and ultimately no one will notice. If you're into House Beautiful, consider glass or ceramics. Otherwise food-grade plastic or SS.

              BTW, did your porkchops taste metallic?

              Aloha,
              Kaleo

              1. re: kaleokahu

                Thanks for the explanation kaleokahu. Are you saying the aluminum oxide formed simply by me taking the pan outside? If the layer is scoured away simply by me cleaning the pan with a sponge/brush and dish soap, then won't I always end up wiping off aluminum oxide every time I clean the pan?

                Is it safe to use Bon Ami on aluminum?

                The food didn't have any metallic taste to it.

                1. re: Citizen_Snips

                  Hi, C_S:

                  No, no, it is likely that the pan either had some oxidation when you bought it, or it had some sort of polish on it to keep it shiny. Your taking it outside wasn't any problem. Passivation layers form quickly--about as fast as you can scour.

                  I keyed off you using Bon Ami and getting black residue back. That is proof you're taking off the oxide. But if you're only occasionally scouring or scotchbrite'ing (i.e., only when that's necessary to clean the pan of food residue) and just using a poly brush or pad and soap most times, you're already doing it right. I think the key is to make peace with the fact that a new aluminum sheetpan should only look new once. ;)

                  And yes, BA is safe to use on aluminum. It is the least abrasive scouring powder I know of. In ascending order of coarseness, it goes BA, Comet, Ajax and Bar Keeper's Friend.

                  Aloha,
                  Kaleo

                  1. re: kaleokahu

                    I believe I may have taken some of the residue off even when I was washing the pan with soap and water. I'm not sure if that makes a huge difference though.

                    1. re: Citizen_Snips

                      Nope, it'll come right back. Ultimately, the sheet will look semi-matte. Enjoy.

                    2. re: kaleokahu

                      In TV shows, many restaurants seem to use what look like unanodized aluminum frying pans to cook just about anything. Other than they being inexpensive, I always wonder if there are other reasons.

                      I bought an 8" one labeled "Satin finish" that has a shiny surface, and have yet to use it. Do I need to season it prior to using? I don't particularly mind if it should lose the shine or turn gray.

                      1. re: eatntell

                        Hi, eatntell:

                        The reason (besides being inexpensive) is that they work really well.

                        Yes, you should season your new pan. Go to the Vollrath website and follow their instructions.

                        Aloha,
                        Kaleo

                        1. re: eatntell

                          <Other than they being inexpensive, I always wonder if there are other reasons.>

                          Inexpensive, and also highly effective. You can season it like what you would do to cast iron or carbon steel pans. However, the seasoning is not as stable.

                          1. re: Chemicalkinetics

                            Thanks for the responses, kaleokahu and Chemicalkinetics.

                            I have a seasoned cast iron pan and love it. But it is too heavy for me to toss it. A few of my non-sticks are so worn out and need replacement. Hence the interest in these unanodized aluminum pans, and also curious about their use in the pro kitchens. Home cooks don't seem to use them or discuss them, and go for the more expensive non-stick anodized ones, or the steel ones instead.

                            Can you elaborate what you meant by "work really well" and "highly effective"? For example, I would expect this aluminum pan to heat up much quicker than a cast iron (takes a long time), but is it any quicker than a non-stick aluminum pan? Once my cast iron reaches the desired heat level, I love the way it maintains it. The flip side is it takes a long time to reduce the heat (when called for). Adding button/wine and scrapping the sticky bits off the pan for thickening the sauce/gravy has been problematic for me for this reason.

                            1. re: eatntell

                              <Can you elaborate what you meant by "work really well" and "highly effective"?>

                              Work well and highly effective because aluminum effectively conducts heat and can provide a very even heating surface.

                              <For example, I would expect this aluminum pan to heat up much quicker than a cast iron (takes a long time), but is it any quicker than a non-stick aluminum pan? >

                              For the same size pan, an aluminum pan heat up quicker than a cast iron pan. It would heat up the same speed as a nonstick aluminum pan unless the two pans are of difference dimension. The nonstick material is very thin to make any real difference.

                    3. re: kaleokahu

                      In regards to passivation, in all my years of metalworking I have never read, nor heard it applied to aluminum. We send stainless parts out for passivation to enhance the corrosion resistance properties. The process used is either citric, or nitric acid which chemically removes any iron that may be present on the surface allowing the chromium layer to totally exposed on the surface of the part.

                      Aluminum anodizes natrually, this is just controlled corossion when done industrially. Aluminum, magnesium, and titanium can also be anodized. My Dad made the anodizing tanks at one of the AF bases he was stationed at. They were doing the propeller bllades for the C-130s, and to test them for coverage they used a multimeter, as anodizing is non conductive. That is why whenver you are TIG welding (or any welding that uses electric arc) aluminum you need to clean the surface down to bare metal , otherwise it will play Hell with the arc.

                      We do agree on the pans here though, wash and dry. Don't worry about a little discolorimg.

                      1. re: BIGGUNDOCTOR

                        Hi, BGD:

                        Well, perhaps you've not heard of passivation with regard to aluminum because there's nothing you need to *do* to passivate it. For pure and mostly pure aluminum, it happens naturally.

                        It is the *alloys* that need help, and so they get electrolytic passivation (a/k/a anodizing). They can also get passivated by alcladding or chromate conversion coating. Compare the Porbaix diagram for aluminum found here: http://www.corrosion-doctors.org/Corr... with the general discussion of alloys here: http://books.google.com/books?id=iEei...

                        Of benefit to those OCD neatniks who scour their aluminum pans to brightness, the latter source indicates that aluminum cookware passivates more easily in fresh water at near-boiling and steam temperatures.

                        But yes, scouring aluminum is a Sisyphean task.

                        Aloha,
                        Kaleo

                        1. re: kaleokahu

                          Everyone I know in the metals industry just calls it anodizing,no matter if it was Natural or mechanical.
                          Different times ,different locations,different terms. In the end it is the same thing being discussed.

                          1. re: BIGGUNDOCTOR

                            Hi, BGD:

                            We started this talking about what happens to aluminum naturally--it forms aluminum oxide. We could call that 'corrosion' as well (which it is), but that would be misleading insofar as it implies an ongoing process, like rusting iron. Aluminum's oxide passivates the surface under normal conditions, and it will not corrode further; iron's oxide--rust--does not.

                            Aloha,
                            Kaleo