Opening a bag of chips to find it only half full is always a disappointment, but it turns out the extra space actually serves a purpose.
The “empty” part of the bag of chips actually keeps the products from going stale too quickly and from the damage of the fragile chips, according to the UK’s Snack, Nut and Crisp Manufacturers Association.
In 2017, a study by CDA Appliances found that the average bag of chips is 72% empty, leaving just over a quarter of the bag for chips.
It turns out, that empty space in your chip bag isn’t just air — it’s Nitrogen gas, which is meant to stop the chips from breaking in the package as well as expel air, which actually turns the chips stale.
There’s even a name for the emptiness — “functional slack-fill.”
“Slack fill occurs [most often] in snacks, nuts, candy. The weight is always accurate,” Robert Niemman, a San Francisco-based lawyer specializing in food-related lawsuits, told Vox. “If it says there’s two pounds in there, there’s two pounds, probably a little bit more. But if the container is designed to hold four pounds and there’s only two pounds in there, obviously it’s only 50% full.”
Considering how fragile chips are, the extra cushioning makes sense to prevent them from becoming a bag of crumbs in transit.
“In addition to preventing staleness, the inserted gas also provides the added benefit of creating a cushioning effect to protect the fragile contents of a packet from damage,” a spokesperson for the Snack, Nut and Crisp Manufacturers Association recently told the Daily Mail in response to the study.
“The packaging expands or contracts depending on the ambient temperature, whereby the gas present in the pack will fill a larger volume when it’s hotter, and a smaller volume when it’s cooler.”
The authors of the 2017 study confirmed that the extra padding in the chip bag did seem to make the snack last longer.
The average bag of chips has a “best before” date of 55 days after production, but the research found that because of the space, one particular brand — Popchips — can last up to 290 days before actually going stale.
Also back in 2017, two snackers sued the brand Wise Foods on the grounds that their air-filled bags deceived them into overpaying.