- Acidic foods can cause aluminum to leach into food, altering taste and safety.
- Tomatoes, citrus, vinegar and apples are too acidic for direct contact with aluminum.
- Use parchment, silicone mats or glass instead of uncoated aluminum bakeware.
I don’t have a dishwasher, so one-pan meals are essential in my household—and few pieces of cookware get as much use as my aluminum sheet pans. I simply toss some protein and vegetables with herbs and spices on a foil-lined pan and pop it into the oven, and I’ve got healthy dinners for the next several days with practically zero cleanup. It seems like a win-win, until I realized that not every food is meant to be cooked directly on aluminum, whether it’s foil or the pan alone.
“We ingest around seven to nine milligrams of aluminum per day through our food, water, the air, dust, soil, antiperspirants and medicines such as aspirin or antacids,” explains Stephanie Smith, consumer food safety specialist and associate professor at Washington State University’s School of Food Science. And while she explains oral exposure to aluminum for many is not harmful, some acidic foods can cause the aluminum to leach into your final dish. For those with kidney disease, this can cause high levels of aluminum to accumulate in your body.
To be on the safe side, Smith identified a few foods to never cook in an aluminum pan and suggested some alternatives for the next time you’re cooking with them.
Why Acidic Ingredients
Transport yourself back to middle school chemistry, and you’ll likely remember the pH scale—which measures how acidic or alkaline everyday items are. For example, battery acid is a 0 on the scale and is strong enough to cause chemical burns. It turns out, many of the foods we eat are on the acidic end of that same scale—and some are rather potent. The more acidic an ingredient, the lower its number on the pH scale, and the more hydrogen ions it has. A high enough concentration of hydrogen can cause aluminum to react, leaching metals into your food and causing a bitter, metallic taste. It can also discolor and even cause pitting on the pan itself.
“I think people mistakenly underestimate the acidity of many foods,” says Smith. When cooking with these ingredients, Smith says it’s best to never cook acidic foods directly on an aluminum surface, regardless of whether you’re using foil or a pan. “Using parchment paper or a silicone baking sheet as a barrier would be the best choice to avoid leaching,” she explains. Here are a few of the worst offenders.
Tomatoes
With a pH of 4, tomato juice is actually more acidic than acid rain and is often found in many recipes. For a particularly saucy dish, it’s likely best to reach for a glass baking dish rather than your aluminum bakeware or sheet pans. For roasting fresh tomato slices or baking a galette, lining the pan with parchment paper will protect it.
Lemons and Other Citrus
Lemon juice is one of the strongest acids we ingest, so it’s best to save a squeeze of citrus for the finished meal once it’s on your plate (or in a ceramic or glass serving dish). Also avoid cooking dishes in aluminum that contain grapefruit or orange juices—while not as acidic as lemon juice, they are still potent.
Vinegar
Similar to lemon and citrus juice, if a recipe calls for a splash of vinegar in a marinade or braise, you’re better off reaching for glass, stainless steel or enameled bakeware. With a pH of 2, it’s a strong acid—which is why it’s often used as a cleaning product.
Wine
The acidity of a wine will vary based on which varietal you’re cooking with, but it’s best to keep it all away from your aluminum cookware. While it is usually fine to deglaze a cast-iron pan with a small amount of wine, that’s not true for aluminum pans and bakeware. Instead, use an enameled dish for long braises, or opt for chicken stock when deglazing.
Rhubarb
Smith called out rhubarb specifically, as it’s a common ingredient in spring baking projects—but surprisingly acidic, especially for a vegetable. The edible stems contain malic acid along with trace amounts of oxalic acid (which can be harmful in large quantities—as found in rhubarb leaves.) When baking pies in aluminum bakeware, use a parchment liner.
Apples
While it may seem obvious that super tart varieties of apples, like Granny Smith, are acid bombs, even sweeter varieties like Fuji still maintain a pH of 3 to 4, which is even more acidic than tomatoes. These varieties taste so sweet, despite the high acid, because they contain equally high amounts of sugar.
The Bottom Line
Aluminum cookware and bakeware are kitchen workhorses, but they shouldn’t be used for cooking with acidic ingredients. Many everyday foods, like apples, lemons and tomatoes, are high in acid and can cause the metals in aluminum to leach into your food or damage the pan. If a recipe calls for an aluminum baking sheet, lining it with a silicone mat (for baking chewy desserts) or parchment paper (for browning and roasting) is recommended. Glass baking pans or stainless steel can also be used.
