# Why don't potato chips go stale in the bag? **URL:** \ **Category:** Factual Questions\ **Created:** [January 17, 2015, 3:22am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045 "2015-01-17T03:22:14Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![obbn](https://avatars.discourse-cdn.com/v4/letter/o/d6d6ee/32.png) [@obbn](https://boards.straightdope.com/u/obbn)\ **Post date:** [January 17, 2015, 3:22am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/1 "2015-01-17T03:22:14Z")
Hello Everyone, I know that food like chips are loaded with preservatives, but if you leave the bag open for a day they will go stale and taste not quite right. Why don’t they go stale in the bag as the bag always contains a good amount of air? ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [January 17, 2015, 3:25am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/2 "2015-01-17T03:25:28Z")
[Packed in nitrogen.](http://www.educationworld.com/a_lesson/showbiz_science/showbiz_science050.shtml) ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [January 17, 2015, 3:25am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/3 "2015-01-17T03:25:32Z")
Maybe the chips are packed in nitrogen? I’m not sure, but that’s certainly a possibility. ETA: Ninjad! ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 17, 2015, 3:41am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/4 "2015-01-17T03:41:48Z")
being packaged in nitrogen they are purged potatoes. ---
**Author:** ![california\_jobcase](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)\ **Post date:** [January 17, 2015, 4:16am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/5 "2015-01-17T04:16:03Z")
I don’t know if the link on nitrogen packing explains it, but chips go stale in a day mainly from absorbing moisture from the air. The gas inside the unopened bag has much less humidity than the outside air. By the way, many stale crispy snacks can be returned to crispy goodness by a quick bake in a 250 F oven. This works particularly well with pretzels and cereals such as Cap’n Crunch. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [January 17, 2015, 6:13am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/6 "2015-01-17T06:13:50Z")
> [@california\_jobcase](#): > > I don’t know if the link on nitrogen packing explains it, but chips go stale in a day mainly from absorbing moisture from the air. The gas inside the unopened bag has much less humidity than the outside air. It’s not just that, but air circulation/exchange. If the bag is open, they’ll absorb moisture, then new moisture will enter the bag and get absorbed into the chips and so on until the chips reach equilibrium with the room. In a closed bag, they’ll absorb whatever is in the bag and then stop. It’s the same reason things last longer (before going stale) if you put them in a ziplock bag or Tupperware container. The nitrogen is dry so that’ll help keep the from getting stale, but it’s also going to be about keeping them from oxidizing and/or going rancid. Barring the rancid/oxidizing thing, if they were to fill the bag with _dry_ air, that would keep them from being stale as well, though that may (I’m winging it here) require a less porous bag. There’s other benefits to using nitrogen, but it’s also probably cheaper to buy nitrogen than to run dehumidifying units to dry air for packing. Refrigeration (which is what a dehumidifier is), is expensive to maintain. ---
**Author:** ![SandyHook](https://avatars.discourse-cdn.com/v4/letter/s/dec6dc/32.png) [@SandyHook](https://boards.straightdope.com/u/SandyHook)\ **Post date:** [January 17, 2015, 11:34pm UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/7 "2015-01-17T23:34:00Z")
Where I live, at least during the summer, chips are good for several days just sitting in a bowl on the table. Doesn’t address the question but generally astounds those who live in more humid areas of the world. ---
**Author:** ![even\_sven](https://avatars.discourse-cdn.com/v4/letter/e/dfb087/32.png) [@even\_sven](https://boards.straightdope.com/u/even_sven)\ **Post date:** [January 18, 2015, 3:25am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/8 "2015-01-18T03:25:41Z")
Seconding that a quick bake can revive many stale foods. In Peace Corps, people would occasionally send me a bag of chips, and not infrequently the packaging would tear at some point in the 3-6 month journey. A quick trip to the oven would usually return them to edible form. ---
**Author:** ![donkeyoatey](https://avatars.discourse-cdn.com/v4/letter/d/e47c2d/32.png) [@donkeyoatey](https://boards.straightdope.com/u/donkeyoatey)\ **Post date:** [January 18, 2015, 3:44am UTC](https://boards.straightdope.com/t/why-dont-potato-chips-go-stale-in-the-bag/710045/9 "2015-01-18T03:44:58Z")
> [@johnpost](#): > > being packaged in nitrogen they are purged potatoes. informative as always (after previous posts)… and love the lack of caps