Food Storage Bags
Recently, Ziploc redesigned our winning food storage bags, so we ran their new bags, the Ziploc Brand Freezer Bags with Easy Open Tabs, through all our original tests. The new bags performed just as well as the old bags at protecting food from freezer burn. But while we liked the “easy-open” tabs, the band of thicker plastic under the double zipper was narrower than the one on the older version, making the new bag harder to prop open and fill. And the seams on the enclosure itself were less sturdy, tearing more easily and making the bag more prone to leaking. If you don’t need your storage bags to hold liquids, the new Ziploc bags ($0.19 per bag) are the best supermarket option. For a better all-around option, though, we recommend Elkay Plastics Re-Closable Heavy Weight Freezer Bags (about $0.10 per bag), which must be ordered online.
How we tested
Why is it so hard to find a good plastic food storage bag? Too often the plastic is flimsy, the closure doesn’t work without a fight, and when you finally get it closed, it leaks. Then there’s the dizzying array of options. Do you need both “storage” and “freezer” bags? Do you want zipper locks or plastic sliders? Expandable bags for bulky foods or double-layer bags for extra protection? One thing, though, is clear: American consumers use a lot of these bags, spending $1.6 billion on them last year alone, according to Chicago market-research firm IRi. A few years ago we picked a favorite bag by Glad: a thick, protective freezer bag with an airtight double-grooved seal. Recently we received conflicting reports from the manufacturer about whether this product was being discontinued. Ultimately we decided that it could no longer hold our top spot, and we went back to the drawing board.
As in our previous testing, we focused on gallon-size bags, in which we store everything from herbs and cookie dough to meat and tomato sauce. We also opted exclusively for freezer bags this time, since past tests have taught us that freezer bags are generally made with thicker plastic, which can keep food fresh longer than the thinner plastic of storage bags. Our wish list: a bag that was easy to seal, leakproof, and durable and that excelled at protecting food. We bought eight products—four sold in supermarkets, two food-service bags sold in bulk via mail order, and two eco-friendly options. Five closed with zipper-lock tracks; three used sliders. Prices ranged from 10 cents all the way up to a staggering 49 cents per bag.
Holding the Bag
Our first criterion: simplicity. You shouldn’t need extra hands to prop up a bag for filling or have to guess if it’s really closed. Bags should swallow up plenty of food and still be easy to seal. To push the limits, we packed each bag with 4 pounds of large carrots. We were able to zip all the carrots into all the bags, and none poked holes in the plastic. But one bag had a petite zipper channel that was hard to match up, while another was tough to keep open because of its dual layers of flimsy plastic; plus, when we flipped over the edges of this bag’s opening (a handy trick to help prop open any bag), its side seams ripped. At least some bags came with useful features—one had a foldout bottom panel that helped it stand up and made it easier to fill. Two bags were particularly sturdy around the opening (one was made of sturdier plastic overall and the other had a wide band of thicker plastic around the top), which made them easy to prop open, and both had deep zipper channels that were effortless to seal.
Next we filled the bags with a gallon of water each and laid them on the counter, noting whether any leaked. To our chagrin, four bags bombed, leaking a few drops—or entire puddles—all over the counter. We didn’t imagine any of them would turn around and prove their worth (and indeed none did, all four falling to the bottom of our rankings by the end of our testing), but we forged ahead with them anyway.
Our next benchmark: an airtight bag that protects the food. The development of freezer burn, indicated by the appearance of brownish-white discoloration on the food and snowy ice crystals, is a visible sign of likely failure in this department. It happens when frozen food dehydrates and oxidizes when it is exposed to air. We froze bags filled with bone-in pork chops, hamburger patties, cookie-dough balls, and sandwich bread. Within two weeks, several bags revealed icy crystals forming on the food, some of which got progressively worse. But in the top-performing bags, scarcely any snowy residue appeared, even after two months.
We sent the bags to a lab to measure their thickness as well as how fast moisture travels through their plastic, called the water vapor transmission rate. A lower, or slower, rate would indicate better protection. But when the results came back, they didn’t reveal a clear trend. Our front-runner, which exhibited only a little residue after two months, had the fastest transmission rate of all the bags, while bags with slower rates, which should translate to better protection, had food that iced up. What was going on? Well, if a bag has a leaky seal, it doesn’t matter how impermeable the plastic is.
So we devised a follow-up test that would also factor in the seal. We weighed desiccant packs (the moisture-absorbing packets found in product packaging), enclosed them in each bag, submerged the bags in water for a week, and then reweighed the packs. One product failed outright—we found the pack floating inside a water-filled bag. The packs in three other bags weighed about 1/2 gram more, indicating that some moisture had gotten in. But four sets—including in our front-runner—stayed remarkably dry, gaining only tenths or hundredths of a gram.
A Blowout Finish
Our last standard: bags that can hold up to abuse. We poured 3⁄4 gallon of tomato sauce into each bag, sealed the bags, and pushed them off the counter. While we don’t expect home cooks to throw around bags of sauce, bags can get knocked around in the fridge or freezer, and accidents do happen. Although four bags exploded, four—our front-runner among them— bounced to the floor without spilling a drop. And finally, we shook each bag briskly three times, both upright and upside down. Our top two bags didn’t leak even a dribble. Interestingly, in both abuse tests, all the failures but one happened at the site of the seal.
Our conclusion: While thick plastic helps, strong seals are more important. The seal on our runner-up, a commercial bag, never blew out; plus its plastic was the thickest in the lineup. It lost a few points in the desiccant test and burst a side seam during the extreme tomato sauce test, but it’s a reliable option if you want to buy in bulk. Our winner features a fail-safe dual zipper and a thick plastic collar that makes it easy to prop open and serves as an improved barrier to air. Leakproof and sturdy, it was also the cheapest bag we tested. And finally, we were pleased to find an environmentally friendly bag we can recommend, too.
We tested eight gallon-size freezer bags, evaluating freezer protection and whether they were leakproof, tough, and easy to handle. Scores were averaged and bags appear in order of preference.
We froze four bone-in pork chops, 2 pounds of ground beef patties, one dozen balls of frozen chocolate-chip cookie dough, and a half-loaf of white sandwich bread for two months, checking them after two weeks, one month, and two months for freezer burn and ice crystals. Bags that kept food in the best condition the longest received high marks.
We pushed bags filled with 3/4 gallon of tomato sauce from kitchen counters and shook bags filled with 1 gallon of water (upright and upside down) to test strength. We checked for damage during routine handling.
To assess bag permeability and the quality of the seal, we weighed packets of moisture absorbing desiccant, sealed them in bags, and kept the bags submerged in water for one week. Then we reweighed the desiccant packs. Drier packets rated highest. Bags also lost points for leaking when filled with 1 gallon of water and laid flat on counter.
EASE OF USE
We preferred bags that were sturdily constructed, making them easier to prop open to fill, and that were easy to securely seal even when very full.
The thickness of a single wall of the plastic bags, measured by an independent laboratory, in mils (1∕1000 of an inch).