Plastic Food Storage Containers

Published May 1, 2010. From Cook's Illustrated.

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Why is it so hard to find a container that’s leakproof, opens and closes easily, and goes from freezer to microwave to fridge to dishwasher without warping or wimping out?

Overview:

Packing up leftovers ought to be easy, but food storage containers are one of life’s persistent little annoyances. Once you dig through a slippery stack of containers to match tops and bottoms that aren’t too stained or warped, you have to fuss over them for a tight seal. Then comes another series of quandaries: Does it fit in the fridge or freezer? Will it leak if it tips over? Can you microwave in it? Do you have to remember to wash it only on the top rack of the dishwasher? Should you worry about possible health risks with plastics containing bisphenol-A (BPA)? Frankly, we don’t think food storage containers should take this much thought or effort.

In search of a caveat-free bottom line, we bought eight 8-cup rectangular and square containers made from purportedly safer BPA-free plastic (most manufacturers, with the notable exception of Tupperware, have produced new lines without this controversial material, which research has linked to health issues including hormonal disorders and cancer). We submerged, froze, refrigerated,… read more

Packing up leftovers ought to be easy, but food storage containers are one of life’s persistent little annoyances. Once you dig through a slippery stack of containers to match tops and bottoms that aren’t too stained or warped, you have to fuss over them for a tight seal. Then comes another series of quandaries: Does it fit in the fridge or freezer? Will it leak if it tips over? Can you microwave in it? Do you have to remember to wash it only on the top rack of the dishwasher? Should you worry about possible health risks with plastics containing bisphenol-A (BPA)? Frankly, we don’t think food storage containers should take this much thought or effort.

In search of a caveat-free bottom line, we bought eight 8-cup rectangular and square containers made from purportedly safer BPA-free plastic (most manufacturers, with the notable exception of Tupperware, have produced new lines without this controversial material, which research has linked to health issues including hormonal disorders and cancer). We submerged, froze, refrigerated, and microwaved them. We dropped them and ran them through dozens of dishwasher cycles. Then we did all the tests again. In a separate series of tests, we tried out three containers made from glass, a worry-free yet heavy and breakable alternative to plastic and its reported health risks.

No Drips

A few decades ago, Tupperware set the food storage standard with seals that close by pressing all around the rim. Today’s trendsetter is Snapware: You put the lid in place and snap down flaps that project like wings from the lid. Five of the eight plastic containers we tested use this newer snap seal; manufacturers hoping to woo converts to this style pledge simpler, tighter, leakproof technology. To test their claims, we filled each container with chicken soup and shook them. Five of the eight containers (including one traditional and two snap seals) kept us dry, but three dribbled. Next, we filled containers with pie weights and sugar and sank them under water; two kept the sugar bone-dry, only one of which also passed our soup test. Not that you’ll be scuba diving with your leftover lasagna, but tighter seals—and so far snap seals were performing at least as well as traditional seals—keep food fresher.

That said, not all snap-type seals are alike. All lids contain a soft silicone gasket embedded in a groove around the perimeter of the lid, but their construction and the flap design determine how tightly and—more important—how evenly the gasket can seal. It mostly comes down to a ridge on the underside of the lid: On better models, this ridge completely encircles the underside, distributing the pressure evenly when the snaps click into place, while leak-prone containers have only sparse sections of ridge, if any.

Easy Does It

Speaking of clicking into place, some containers were easier to close than others. Some took force to snap—threatening pinched fingers—and a lot of wiggling to align the lid. One particularly fussy unit wouldn’t close unless its lid was fitted in a particular (yet poorly indicated) direction. All you want here: a container whose flaps slip into place neatly and firmly.

Besides a snug lid, there are a few other practical concerns. First, odor absorption. Nobody wants a container that smells like yesterday’s tuna salad, so we refrigerated oil-packed tuna for three days, ran containers through the dishwasher, and sniffed. One of the “disposable” supermarket containers retained a whiff of fish. Most of the glass and polypropylene containers were fine.

Second, a truly convenient storage container should cope with the freezer or microwave without warping, melting, or staining. We froze chili, then microwaved the containers until hot. We detected no plastic scents or flavor, but one “disposable” container softened and then rehardened as it cooled (would we really like to eat that chili?); another’s snap flaps warped—and then wouldn’t lock. Chili stained them all, but a few dishwasher cycles removed most traces.

Third, a storage container is serviceable only if it fits in the prescribed storage space. After weeks of cramming containers into freezers and refrigerators, we preferred low, flat rectangles that slide onto any shelf, leaving room for other items, and simple, stackable flat—not bulbous—lids. But there’s also a food-quality reason to opt for flat: more efficient chilling and heating. After 24 hours in the freezer, water in tall containers was still liquid at the center but frozen solid in lower, flatter models. In the microwave, the chili in deep containers overheated at the edges before heating through in the middle.

Time Will Tell

All these features should be basic to a new container, but a really good one should retain them over time. We put our lineup through 50 home-dishwasher cycles to simulate about a year of use, noting which came with top-rack-only instructions. Then we repeated our tests—and found disparate results: All our heating, chilling, and washing had damaged a few models, warping their lids and loosening their seals. The only container to pass both leak tests the first time did so again, but only after painstaking efforts to lock the seal, indicating a lack of durability. Meanwhile, some brands—including our three top-rated containers—actually sealed better. Polypropylene is extruded and molded to make these containers, and heating can correct small irregularities.

One container worked nicely out of the box, survived all our tests, and met all our long-term goals. Our winner sealed tightly and easily; resisted warping, stains, and smells; and fit easily among the contents of our refrigerator. It performed well before taking more than 50 baths—and perfectly afterward. This might be the last container we’ll have to buy for quite a while.

Methodology:

We tested eight BPA-free plastic (according to manufacturers) food storage containers, choosing square or rectangular sizes as close as possible to 8-cup capacity. All were purchased online or in Boston-area retail stores.

LEAKS

We filled the containers with chicken noodle soup and shook them vigor- ously for 15 seconds, then filled them with sugar and pie weights and sub- merged them in water for two minutes. Containers that didn’t leak in the soup test and that kept their contents dry when submerged received high marks.

ODORS

We refrigerated oil-packed tuna in each container for three days, then ran containers through a home dishwasher and checked for odors.

MICROWAVE

We filled containers with chili, froze them, and reheated them in the micro- wave, checking for warping, staining, and plastic flavors or odors.

DURABILITY

After testing, including 50 cycles in a home dishwasher, we observed stains, warping, and wear and tear; then we froze water in the containers and dropped them from chest height.

DESIGN

We considered features that made the containers easier to use, including simple, intuitive seals or efficient shapes.

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  • Product Tested

    Results Key:

    Good ★ ★ ★ Fair ★ ★ Poor
  • Prices are subject to change.
  • Highly Recommended - Winner

    Snapware Airtight

    Simple snap-down lid sealed easily throughout testing. Though it allowed a few drops of water during its first submersion test, after dishwashing, seal was perfect. Flat, rectangular shape encourages quick cooling or heating and stacks easily, with lid attaching to bottom. *Since our testing, the company has changed its name from Snapware Mods (but that's all that's changed).

    • Leaks ★★½
    • Odors ★★★
    • Design ★★★
    • Microwave ★★★
    • Durability ★★★

    $7.99

    BUY NOW Amazon
  • Recommended

    Lock & Lock Classic Food Storage Container

    Sturdy, with secure seal. Performed dependably overall but leaked a few drops during first submersion test—though seal improved after dishwashing 50 times. Stained slightly more than others after microwaving chili, and has taller, deeper shape that we find less practical.

    • Leaks ★★½
    • Odors ★★★
    • Design ★★
    • Microwave ★★
    • Durability ★★★

    $7.49

    BUY NOW Amazon
  • Recommended

    OXO Good Grips LockTop Container

    Instead of employing flaps, seal works by pressing down single piece of plastic trim around lid. Leaked when submerged when new, but after dishwashing 50 times, seal improved (though lid bowed, making it stiffer to seal). Stained slightly more than other containers and has taller, deeper shape than preferred.

    • Leaks ★★½
    • Odors ★★★
    • Design ★★
    • Microwave ★★
    • Durability ★★½

    $7.99

    BUY NOW Amazon
  • Recommended

    Freshvac Pre Vacuum Food Storage

    We struggled to achieve perfect airtight seal after dishwasher test—unless lid was aligned right, "vacuum" tab wouldn't operate. Shape is low but too rounded and bulbous for efficient storage. Miniscule "date dial" popped off during dropping test.

    • Leaks ★★★
    • Odors ★★★
    • Design
    • Microwave ★★
    • Durability

    DISCONTINUED

  • Recommended with Reservations

    Gladware Deep Dish

    Performed acceptably new but became alarmingly soft in microwave. After 50 dishwasher washes, it degraded: Seal leaked profusely, chili stained, and fishy odor hung on. Best for a potluck$#2014;it's cheap and you won't care if you don't get it back.

    • Leaks ★★
    • Odors
    • Design ★★
    • Microwave
    • Durability

    $5.97

  • Not Recommended

    Sterilite Ultra-Seal

    We had high hopes for this container, but seal was uneven; because lid lacked rigidity, corners leaked badly even when new. (Second new model had same flaws.) Flap popped open during drop test. Chili stained more than in other containers.

    • Leaks
    • Odors ★★★
    • Design
    • Microwave ★★
    • Durability

    $6.49

  • Not Recommended

    Ziploc Snap 'N Seal

    Despite being roomy, felt cheap and flimsy. Extremely leaky in soup and submersion tests, both before and after 50 dishwasher cycles. Not on a par with better containers in lineup, or even with fellow "disposable" containers by Glad. Its only virtue: rock-bottom price.

    • Leaks
    • Odors ★★★
    • Design
    • Microwave
    • Durability

    $4.55 for set of 2

  • Not Recommended

    Rubbermaid Lock-its

    Usually dependable brand floppedߞpoorly made flap seals distorted in microwave, popping back up when pressed down, trapping us in an endless game of Whack-A-Mole. (Second model shared these flaws.) Top flew off in drop test. We like "Easy Find" lid, which sticks to bottom of container, but that was its only asset.

    • Leaks ★½
    • Odors ★★★
    • Design ½
    • Microwave
    • Durability

    $12.99

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