Why You Should Remove the Seal Under the Lid of a Food Container

Food products, especially dairy options like yogurt and sour cream, may have a plastic or foil seal under the lid. You might wonder whether you should remove this seal when you open the product or keep it in place for extra coverage.

Here’s why the foil or plastic seals on food containers exist in the first place and why removing it actually helps keep your product fresher, according to experts.

“There are two reasons for the seal,” says Jason Tetro, a microbiologist and the author of The Germ Files and The Germ Code, who’s based in Edmonton, Alberta. “Firstly, it helps to increase shelf life — the container is usually flushed with nitrogen before sealing, which reduces the amount of oxygen inside.”

The second reason is to protect the contents of the container: “It helps to prevent the introduction of chemicals and microbes that could spoil the products or cause illnesses,” Tetro says.

The microbial ecologist Jack Gilbert, PhD, a professor at the University of California in San Diego, who’s based in Encinitas, California, further explains that the seal acts as a safety and quality mechanism because it creates a barrier between the product and the external environment.

Lastly, the seal indicates to consumers that the product hasn’t been tampered with prior to purchase, Dr. Gilbert says.

For several reasons, Tetro recommends removing the plastic or foil safety seal as soon as you open the product.

“Once the seal is broken, the surrounding air and oxygen can get into the product, and that will start up the microbial growth,” says Tetro. “Whether the seal is still there or not [after it’s been opened] isn’t a factor. Its sole purpose is to get [the product] from the factory to your kitchen safely.”

What’s more, keeping the seal on the open product can lead to a higher risk for contamination from continual touching, according to Tetro.

It’s best to always wash your hands before handling any food products. And toss the plastic or foil safety seal on items like yogurt or cottage cheese into the trash after you first open the product, just to be safe.

• Remove the plastic or foil seal from food containers after opening, as leaving it on may increase the risk of contamination from repeated touching.
• The seal serves to prevent microbial growth and chemical exposure only before the product is opened, not after.
• Always inspect food safety seals before purchase to ensure they haven't been tampered with or damaged.