Nitrogen flushing is a preservation method used to protect packaged foods, such as coffee beans, nuts, rice cakes, snack crackers and chips.
When you've picked up a bag of chips at the grocery store, you've probably noticed the bag is puffed and filled with 'air.' But it's not exactly like the air we breathe -- the package doesn't contain oxygen.
When processed food is exposed to oxygen, it deteriorates - oils go rancid, discoloration occurs and the food spoils. Oxygen can be removed from the packaging by removing all of the air with a vacuum, which will increase the shelf life of the food packed inside.
Regular vacuum packaging works fine for sturdy solid foods like beef jerky and fresh meat, but it doesn't work well for foods that are delicate, like snack chips and crackers. These foods need protection during transportation, so they won't be crushed or broken. Food manufacturers use nitrogen flushing and sealing machines to force the regular air out of the packaging and inject nitrogen gas into the packaging.
Nitrogen doesn't react with food like oxygen does, so foods stay fresher longer and it doesn't affect the flavor or texture of the food. Since the nitrogen fills up the bag, it helps to protect the delicate foods inside. Of course, once you open the bag, the food is no longer protected and will start to deteriorate; however you can maintain some of the freshness by keeping the package closed with a twist tie or clip, or by placing the food in a resealable container.