Why You Shouldn’t Store Food in an Open Metal Can

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. The temptation to simply cover it with plastic wrap and pop it into the fridge is strong. But is this a safe practice? While it may be tempting, you might want to think twice before doing so. Here’s what you need to know about the potential risks of storing food in open cans and the best practices for keeping your leftovers safe and flavorful.

Are There Dangers to Storing Food in an Open Metal Can?

The Department of Agriculture states that “unused portions of canned food may be refrigerated in the can” but quickly follows up with a crucial caveat: “To preserve optimum quality and flavor, place the unused portion in a food-grade glass or plastic container.” Why is this so important? In the same way you’d never store your sheet-pan salmon on the pan you cooked it on, it just wouldn’t be as good. The quality will undoubtedly deteriorate. And even if it’s technically safe, you might face health risks over time. Jennifer Pallian, a registered dietitian and food science writer with more than 15 years of test-kitchen experience, advises against storing food directly in the can, explaining that 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 foods are created equal. Pallian notes, “The safety of storing food in open cans varies depending on the type of food. Acidic foods, like tomatoes, can cause more leaching of chemicals from the can’s lining compared to nonacidic foods, like beans.” According to the USDA, “metal cans … are made of sheet steel—sometimes with a coating of tin.” Research suggests that prolonged storage and exposure to oxygen in acidic foods can lead to increased leaching of metals, like iron and zinc, potentially impacting food safety. Ultimately, the longer food is stored, especially in acidic conditions, the higher the risk of metal leaching due to corrosion. So, it’s especially important to transfer acidic canned foods to alternative containers after opening. 

What’s the Deal with BPA?

According to the Food and Drug Administration, bisphenol A (BPA) is “a chemical used in certain food contact materials and first approved by FDA in the early 1960s. In recent years, concerns have been raised about BPA’s safety.” But the FDA’s current position is that BPA is safe at the levels found in foods today. Since there still seems to be a lot of debate among researchers about whether there are any safe levels of BPA in canned foods, Pallian thinks that we should avoid that risk entirely. “Storing food in opened cans increases the risk of BPA leaching into the food,” she says, which can significantly impact our health. And her concerns are warranted. Research suggests that BPA can even have the effect of mimicking estrogen, which may disrupt hormone function. Beyond that, once a can is opened, the environment inside becomes compromised. “Canned foods are typically processed to be sterile. Opening the can breaks this sterile environment, allowing bacteria to enter and proliferate,” Pallian adds. This increased exposure to air introduces moisture and microbes, potentially leading to foodborne illness (aka food poisoning).

How About BPA-Free Cans?

Products labeled as “BPA-free” are typically replaced with chemicals like bisphenol S (BPS) and bisphenol F (BPF). They provide similar properties, such as durability and heat resistance, without the negative press associated with BPA. However, BPS and BPF are structurally similar to BPA and have shown similar endocrine-disrupting effects. Further research is still needed regarding their long-term health and safety. But the benefits of canned foods outweigh the risks. They’re convenient, loaded with nutrients and can transform into hearty meals in no time. Besides, unless you’re committed to making your beans and marinara from scratch, BPA-free cans are the best option (at this point) to avoid BPA. To ensure your packaging is BPA-free, look at the “resin code.” A resin code is a stamp or marking similar in appearance to the triangular recycling symbol. If the number 7 appears in the center of this symbol, it means that the container likely contains BPA.

Food Safety and Best Practices

To summarize: While leftovers can technically be stored in the can, the type of food and storage time can impact the quality and safety. Given these potential risks, here are some food-safety best practices for storing leftover canned goods.

• Transfer to proper containers: The USDA recommends transferring leftover canned food to clean, airtight containers made of glass, plastic or stainless steel.
• Refrigerate promptly: Get those leftovers into the fridge within two hours of opening the can.
• Do occasional temperature check-ins: To slow bacterial growth and preserve freshness, your refrigerator should always be at 40°F (4°C) or below and your freezer at 0°F (-18°C) or below. Consider keeping a thermometer in your fridge and freezer so you always know the temperature is in the safe zone. Alternatively, schedule a quarterly checkup where you check the temperature of these places to ensure they’re up to snuff.
• Label and date: Mark your containers with the date of storage to keep track of freshness and how long they’ve been in the fridge or freezer.
• Use within 3 to 4 days: Consume any leftovers within this time frame for optimal safety and quality. Always err on the side of caution, and consult this handy chart whenever you’re unsure. 
• Consider freezing: For longer storage, transfer food to freezer-safe containers and freeze.

What Types of Containers Should I Use?

“Ensure containers are clean, dry and airtight,” says Pallian. When it comes to storing leftover canned foods (or leftovers, in general), consider using glass, stainless-steel or ceramic containers (which are all nonreactive) with tight-fitting lids. Opt for durable, airtight sets when possible. And if you’re using plastic containers, choose BPA-free containers and resealable plastic bags for freezing. Anything that doesn’t meet these standards can be recycled.

The Bottom Line

Canned goods are healthy, convenient, delicious, budget-friendly and reliable sources of quality food and something we won’t stop reaching for anytime soon. While storing leftovers in their original container might be convenient and safe up to a point, the potential risks to both food quality and your health make it a practice best avoided. By taking a few extra moments to transfer your food to a proper storage container, you’re preserving its flavor and protecting yourself from potential chemical exposure and bacterial growth. So, the next time you’re tempted to pop that open can into the fridge, take a moment to transfer its contents to a suitable container. At the very least, you’ll be doing your taste buds a favor and, on the other end of the spectrum, safeguarding your health.