5 Foods Scientists Say to Never Wrap in Foil
Key Points
Avoid using aluminum foil with acidic or salty foods due to leaching risk.
Tomatoes, citrus, vinegar and cured meats can react with and damage foil.
Foil is best for steaming, not for crisp-roasting vegetables.
Aluminum foil is a true kitchen workhorse—whether I’m tenting a roast chicken to preserve perfectly crisp skin or making cleanup painless after a weeknight sheet-pan dinner, it’s rare that a box of foil isn’t hanging around on my counter.
However, after learning about what shouldn’t be cooked on aluminum sheet pans earlier this year, I realized that aluminum foil may not always be the best tool for some of these jobs. Certain acidic and salty foods can react with aluminum in ways that affect both food quality and flavor, explain food scientist Abbey Thiel and recipe developer Emmy Clinton.
Some can even cause aluminum to leach into your food, which isn’t ideal in large amounts. According to the Centers for Disease Control and Prevention, the average person consumes around 7–9 milligrams of aluminum per day through food. While generally safe for healthy individuals, those with kidney disease may have a harder time excreting it, which can lead to accumulation in the body.
With food quality and safety in mind, here are the foods our experts said are better off wrapped in something else.
1. Tomatoes & Tomato Sauce
Acidic foods can break down the protective oxide layer on aluminum foil—and tomatoes are surprisingly acidic, says Thiel. In fact, tomato sauces often have a pH of 4.0–4.6, though most people don’t realize how acidic these sauces can be due to the other ingredients included in them.
“At a basic level, aluminum foil is made of metallic aluminum, but it’s actually protected by a very thin, stable layer of aluminum oxide on the surface. This layer is what normally keeps aluminum from reacting with everything it touches,” Thiel explains. “The issue is that acid and salt can break down that protective oxide layer. Once that layer is disrupted, the underlying aluminum metal is exposed and can start to react.”
Instead of foil, Thiel suggests using glass or ceramic baking dishes for lasagna, baked pastas or braises in tomato-based sauces.
2. Citrus
Similar to tomatoes, citrus fruits like lemons, limes or oranges (and their juices) are also acidic, and the citric acid they contain can accelerate the leaching reaction. “I avoid cooking anything citrus-based in aluminum foil because they are highly acidic and can end up making the final product taste metallic,” says Clinton.
This is especially true for marinades that contain lemon or orange juice. One study found that marinated foods consistently pick up more aluminum than unmarinated foods. To avoid leaching in these recipes, marinate foods in glass or ceramic, then use parchment paper as either a barrier or envelope for steaming, depending on the recipe you’re following.
3. Vinegar-Based Foods & Marinades
Vinegar is another acidic ingredient that can break down aluminum foil’s protective layer, Thiel explains. Vinegars consist primarily of water and acetic acid, which forms when organic materials are fermented, such as grape must (balsamic vinegar), rice (rice vinegar) or apples (apple-cider vinegar).
With that in mind, avoid using aluminum foil to cover salad dressings or marinades, opting for a glass container with a lid instead.
4. Cured & Brined Meats
It’s not just acids that can break down that protective oxide layer—salt can also destabilize it, especially during long cook times. Foods that are especially salty—like a cured ham or brined poultry—shouldn’t be wrapped in foil for that reason.
“The foil is normally protected, but acid and salt strip away that protection, and once that happens, very small amounts of aluminum can slowly dissolve into the food,” says Thiel.
5. Roasted Vegetables
Cooking vegetables in aluminum foil (as long as they aren’t covered in salt or something acidic) is perfectly safe—but may not yield the tastiest results. “I see people wrap their veggies that want to be browned in foil. This ends up steaming them and making them mushy, when the goal is a beautiful crisp,” Clinton explains. Essentially, the foil traps moisture and prevents caramelization, which is what gives roasted vegetables their deep flavor.
If you’re looking to bake a potato or an ear of corn, wrapping it in foil will help soften it, but if you’re looking for crispy edges, it’s best to roast them uncovered on a sheet pan. For easy cleanup, Clinton suggests lining the pan with parchment paper or a silicone mat.
Our Expert Take
A box of aluminum foil is still worth keeping on hand—just not for everything you cook. In most cases, wrapping your food in foil is safe, but it’s best to avoid acidic or salty foods that can break down the foil’s protective layer, potentially allowing it to react with food. Some of the main offenders are tomatoes and tomato-based dishes, citrus fruits, vinegars and cured or brined meats.
From a culinary standpoint, aluminum foil is best for steaming and trapping moisture. So, if you’re trying to roast vegetables or achieve a perfectly crisp chicken skin, it’s better to leave them uncovered on the sheet pan.
Instead, use ceramic or glass dishes, or opt for parchment paper or a silicone mat for sheet pans. These simple swaps can help your food taste better and maintain quality.
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