everyday chemistry – Can we fill potato chips bags with a gas other than nitrogen?

The Question :

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I understand that we fill potato chips bag with nitrogen to prevent oxidation. But why do we use nitrogen, instead of neon or hydrogen or something else?

My first guess is that nitrogen is lighter than neon/argon but what about hydrogen or helium?

The Question Comments :
  • Because nitrogen is cheap.
  • And doesn’t explode.
  • Hydrogen? So you want chips bag floating around like balloons and have to be hold down?
  • Nothing is better than chips freshly baked in hydrogen flame.
  • From personal experience (traveling to a number of different customers in behalf of Lako Tool to install heated bag crimpers (“sealing jaws”) on vertical form, fill, and seal wrapping machines), I have never seen any gas nozzles that would fill the bags. In fact, that could inflate the bags and therefore interfere with the sealing process.

The Answer 1

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As Nilay Ghosh said, nitrogen is cheap. Very cheap. Neon is expensive. Argon is cheaper than neon, but considerably more expensive than nitrogen. Helium is also expensive and needs to be used wisely, for important things, e.g., cryogenics. And hydrogen! I can just see the ads: “Buy our chips: they are lighter than air! But avoid open flames and sparks unless you want to be Hindenburged to a crisp (no pun intended)”

Another fill gas to avoid is sulfur hexafluoride. A tennis ball manufacturer once decided to fill tennis balls with sulfur hexafluoride, assuming this would prevent the balls from going flat as a consequence of the high molar mass of sulfur hexafluoride. But the tennis balls exploded on the shelves because air diffused in.

Thankfully, no one has ever tried using nitrous oxide as the fill gas in potato chip bags!

The Answer 2

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Not mentioned yet: nitrogen is entirely non-toxic, environmentally friendly, does not contribute to global warming or ozone depletion.

In very good approximation, nitrogen is just air with the oxygen removed that would oxidize the contents. The usual production process consists of liquefying air, distilling it, and then selling the gases separately. This makes food-quality nitrogen very cheap. It’s not a huge problem if there’s 1% oxygen left in the bag.

The Answer 3

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Substances that are gaseous down to, say, -10 are finite (and not very large) number.

Of these, we want:

Safe against ignition (so no hydrogen or gaseous hydrocarbons)

Not poisonous (phosphine, arsine, carbon monoxide – out!)

Not corrosive (chlorine, fluorine – sorry)

Without unpleasant smell (hydrogen sulfide is no-go)

Not related to processes of food degradation (oxygen)

Low diffusion in everything, in order to stay into the package (helium, go home – but sometimes used in cans)

Environmentally friendly (CFCs and friends – great if it wasn’t for ozone layer)

Cheap (krypton, xenon – stay away from our mass products)

A lot of them fail more than one of the above.

And those that pass, have to be approved by local food quality regulator.

What we have left:

Nitrogen – numero uno for inert packaging. Cheap as hell, inert for all practical purposes.

Carbon dioxide – a bit more expensive, easier logistics (lower pressure tanks), less suffocating potential (heavier than air and has some smell), alters the taste a bit (but not always bad – see soda drinks).

Argon – adds a touch of luxury, otherwise just like nitrogen. Sometimes just not separated from nitrogen. I have seen it used in an occasion when nitrogen is off.

Air – cheaper than nitrogen and still contains ~80% nitrogen. Sometimes mixed with nitrogen in order to get the oxygen down to acceptable level.

p.s. other gases can be food-grade as well, including, but not limited, to hydrogen, nitric oxide, sulfur dioxide, oxygen, ammonia. They are used for other purposes in the food industry, but not for packaging.

The Answer 4

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The reason to employ nitrogen in place of air, in addition to a cost advantage, is the fact that air contains oxygen, possibly water vapor, dust particles (containing trace amounts of transition metals) and even microbes (bacteria, mold spores,…) as well.

Upon warming with time, I would not expect that such a mix is a good inert medium to store/preserve food.

While using hydrogen may provide some marketing hype, my experience is that the gas is very adept at escaping and any mixing with air followed by accidental ignition may result in burns. So just adding pure N2 from liquid nitrogen is probably a better idea.

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