We’ve all been there: you open a can of tomatoes for a new sauce or chili recipe, only to realize you don’t need the whole can. It’s tempting to just cover the can with plastic wrap and put it in the fridge, but is that a safe way to do it? While it may be tempting, you may want to think again. Here’s what you need to know about the potential risks of storing food in open cans, and the best ways to keep your leftovers safe and tasty.

Is storing food in open metal cans dangerous?

The Department of Agriculture states that “unused portions of canned foods can be refrigerated in the can,” but quickly adds an important caveat: “To preserve optimal quality and flavor, transfer unused portions to a food-safe glass or plastic container.” Why is this so important? Just as you would never store your salmon in the pan you cooked it in, it simply wouldn’t be as good. The quality would undoubtedly deteriorate. And even if it technically safe, but you could be exposed to health risks over time. Jennifer Pallian, a registered dietitian and food scientist with more than 15 years of experience in test kitchens, advises against storing food directly in cans because it “can pose several health risks, primarily due to chemical contamination and microbial growth.”

Does the type of food matter?

When it comes to storage risks, not all canned goods are the same. Pallian notes, “The safety of storing food in open cans depends on the type of food. Acidic foods like tomatoes can cause more chemicals to leach from the inside of the can than non-acidic foods like beans.” According to the USDA, “Metal cans… are made of sheet steel—sometimes with a tin coating.” Research suggests that prolonged storage and exposure to oxygen in acidic foods may lead to increased leaching of metals such as iron and zinc, potentially compromising food safety. Ultimately, the longer food is stored, especially in acidic conditions, the higher the risk of metal leaching through corrosion. It is therefore particularly important to transfer acidic canned goods into alternative containers after opening.

What is the problem with BPA?

According to the U.S. Food and Drug Administration, bisphenol A (BPA) is “a chemical used in certain materials that come into contact with food. It was first approved by the FDA in the early 1960s. In recent years, concerns have been raised about the safety of BPA.” However, the FDA currently believes that BPA is safe in the amounts found in food today. Since there still seems to be a big debate among researchers about whether any Although there are safe levels of BPA in canned foods, Pallian believes we should avoid this risk altogether. “Storing food in opened cans increases the risk of BPA leaching into the food,” she says, which can have significant impacts on our health. And her concerns are justified. Research suggests that BPA may even have the effect of estrogen, which can affect hormone function. In addition, the environment inside a can is compromised once it is opened. “Canned goods are normally processed in a sterile manner. Opening the can destroys that sterile environment, allowing bacteria to enter and multiply,” adds Pallian. The increased exposure to air allows moisture and microbes to enter the cans, potentially leading to foodborne illness (also known as food poisoning).

How about BPA-free containers?

Products labeled “BPA-free” are usually replaced with chemicals such as bisphenol S (BPS) and bisphenol F (BPF). They offer similar properties such as durability and heat resistance, but without the negative reputation associated with BPA. However, BPS and BPF are structurally similar to BPA and have shown similar endocrine-disrupting effects. More research is still needed regarding their long-term health and safety. But the benefits of canned foods outweigh the risks. They’re convenient, packed with nutrients, and can be turned into hearty meals in a snap. Plus, BPA-free cans are (for now) the best option for avoiding BPA, unless you like to make your own beans and marinara. To make sure your packaging is BPA-free, look for the “resin code.” A resin code is a stamp or mark that resembles the triangular recycling symbol. If the number 7 appears in the center of that symbol, it means the container likely contains BPA.

Food safety and best practices

In summary, while leftovers can technically be canned, the type of food and storage time can impact quality and safety. Given these potential risks, here are some food safety best practices when storing leftover canned food.

• Transfer to suitable containers: The USDA recommends transferring leftover canned goods to clean, airtight containers made of glass, plastic or stainless steel.
• Refrigerate immediately: Place leftovers in the refrigerator within two hours of opening the can.
• Carry out occasional temperature checks: To slow bacterial growth and maintain freshness, your refrigerator should always be kept at a temperature of 4°C or less and your freezer at a temperature of -18°C or less. Keep a thermometer in your refrigerator and freezer so you always know the temperature is within safe limits. Alternatively, you can schedule a quarterly check-up where you check the temperature of these places to make sure they are up to standard.
• Label and date: Label your containers with the storage date to keep track of freshness and how long they will last in the refrigerator or freezer.
• Use within 3 to 4 days: Use up any leftovers within this time frame to ensure optimum safety and quality. Always play it safe and consult this handy chart if you’re unsure.
• Consider freezing: For longer storage, transfer foods to freezer-safe containers and freeze.

What types of containers should I use?

“Make sure containers are clean, dry and airtight,” advises Pallian. If you’re going to store leftover canned goods (or leftover food in general), consider using containers made of glass, stainless steel or ceramic (all of which are non-reactive) with tight-fitting lids. Opt for durable, airtight containers whenever possible. And if you use plastic containers, choose BPA-free containers and resealable plastic bags for freezing. Anything that doesn’t meet these standards can be recycled.

The conclusion

Canned foods are healthy, convenient, delicious, affordable and a reliable source of quality. Food and something we won’t stop reaching for anytime soon. While it can be convenient and safe to store leftovers in their original container to a certain extent, it’s best to avoid doing so due to the potential risks to food quality and your health. By taking a few extra minutes to transfer your food to a suitable storage container, you’ll preserve its flavor and protect yourself from potential chemical exposure and bacterial growth. So next time you’re tempted to put that opened can in the fridge, take a moment to transfer the contents to a suitable container. At the very least, you’ll be doing your taste buds a favor and protecting your health in turn.