At Least Where Freshness Is Concerned
I had to wince the other day as I watched a friend “reseal” a resealable plastic bag containing shredded cheese. She took out a handful of cheese and then just zipped the bag closed and stuck it back in the refrigerator. “But isn't that what you're supposed to do with a resealable bag,” you ask? The answer is an emphatic “no!” When that bag went back in the fridge, it looked like a little plastic pillow. It was absolutely full of air.
I thought everybody knew better, but apparently I was mistaken. There is nothing that will render food stale or spoiled faster than prolonged exposure to air. Why do you think they make “resealable” bags in the first place? It's so you can seal in the freshness by sealing out the air. And my friend just sealed a whole bagful of air in with her shredded cheese.
Air, or more precisely the oxygen in it, causes all manner of nasty things to happen to stored food. “Oxidation” is what the scientific types call it, and it can make fatty foods go rancid and promote changes in color, texture and flavor in many other foods.
Biting into a limp, rancid-tasting potato chip is bad enough, but even worse things can occur in the presence of air. A sealed plastic bag full of air is a marvelous growth environment for airborne microorganisms like bacteria, molds and yeasts. And, since air usually brings moisture to the party, it's like a trip to the beach for those little critters that cause microbial spoilage. Which is, by the way, the number one cause of good food going bad.
Let's take that air-filled bag of cheese, for example. If my friend were to just leave that cheese out in the open air, it could start to spoil within a few hours. By sealing the air in with the cheese, she's pretty much guaranteeing a rapid decline in quality, to say nothing of safety. Refrigerating it is not the answer. All though it helps, some agents of spoilage aren't impressed by temperature until it gets down to sub-freezing levels. No, they'll just chill out and start covering the cheese with green and white mold. Next time she opens that bag...oooh, surprise!
Speaking, as we were, of potato chips, I'm sure you've noticed that they come packed full of air right from the factory. As a matter of fact, a common complaint is that there's more air in the bag than there is product.
But, it's not really regular ol' air that's taking up all that slack space, as they call it in the snack food industry. It's actually nitrogen gas. Seems that back around 1994, researchers discovered that exposing chips and such to nitrogen made them taste better for longer. So the industry started sealing chips in a nitrogen-infused environment to keep them crisp and tasty as opposed to soggy and nasty. Which is what you get when you open a bag of snacks and put it back in the cupboard or pantry without expelling all the air you let in when you opened the bag. No, you can't replace the nitrogen, but at least if you expel the excess air before you seal the bag with a chip clip or whatever, you'll preserve the taste and texture for far longer than if you trap air inside the bag. Same thing applies to cookies and crackers and snack cakes. They probably won't “go bad” as in “kill you deader than a hammer” bad or even make you sick as a dog bad, but they sure won't be as appealing after a few days in an air-filled environment.
And how about those leftovers you put in the zip-top bag? Did you just fill the bag with food and then top it off with a nice layer of air? Might as well have not bothered with zipping up the bag.
Same thing, by the way, if you're using plastic or glass storage containers with lids. Don't just snap the lid on after you fill the container. The makers of Tupperware used to highlight a little feature on the lids of their products that allowed you to “burp” them to get rid of any air inside before you sealed the container. You don't have to have a special “burp” button, just press down on the lid a little before you seal the bowl.
Whether it be cheese or chips or cookies or leftover veggies, it only takes a second to squeeze the air out of the bag – or bowl – before you seal it up. You have to develop the habit of doing it until it becomes instinctive. Muscle memory. Expel the air then seal the container. I've been doing so long that I don't even have to think about.
Now, I'm not saying you have to be a real fanatic about it. Just press or roll the bag until you get as much air out as possible. You're never going to get all the air out; just aim for doing the best you can.
Some folks swear by the water displacement method, whereby you partially seal your seal-able bag and then lower it into a pot of water, allowing the water pressure to push out any air in the bag before you finish sealing it. This is a tried and true method that works well with zip-top bags and such, but I wouldn't recommend it for sealing up an open bag of Doritos.
Then there are questionable tips like leaving an open corner and using a straw to suck the air out of the bag. Meh. That one's been around for a while. No less a resource than the venerable Good Housekeeping magazine actually recommended it at one time. But, I don't care if you just rinsed your mouth with a quart of Listerine, there's gonna be a few germs left in your oral orifice and do you really want to give them a free ride down into your leftovers? Just sayin'.
You could go off the deep end and buy a vacuum sealer. Greatest thing since sliced bread if you're into sous vide cooking (which I am) or if you buy in bulk and want to put stuff up for freezing (which I do.) As you might have guessed, I have one. But even I'm not dedicated enough to the cause of freshness to use it for day-to-day things. Besides the cost of endless vacuum sealer bags, I'm not sure how well the process would work with potato chips. I'm sure whatever crumbs would be left after the sealer got through with the chips would be undeniably fresh, but.....you know. (Actually, I saw a gadget online the other day – a mini bag sealer – that does nothing but seal the kind of bags that chips and snacks come in, but....really?)
No, just stick with pressing the air out and then sealing the bag/container as quickly as you can. As I said, you're not gonna get all the air out, but you'll do a helluva lot better of keeping your food nominally fresh than if you just chunk little air-filled plastic pillows into the refrigerator or pantry.
Remember, when it comes to food freshness and safety, it's far better to expel than to leave an air cell. (I know; it's a stretch but it's the best I could do.)
