An unopened box of breakfast cereal, such as Post or Kellogg’s, is packaged airtight and will keep for a long time. In many cases, the best-by date is at least a year out from your date of purchase, if not more.
When using airtight food containers, opaque ones are best. Exposing any type of cereal to light causes the oils to break down and also causes starches to turn brown, both of which shorten the overall shelf life of your cereal.
Mason jars are just another airtight container, but they’re a common method of food storage for dried goods. As with other airtight containers, opaque or amber-colored jars are far better than clear ones since they block light.
In most cases, storing an open box of cereal in the freezer won’t buy you more than six months. Beyond that, the taste and texture of your cereal diminishes.
Using a vacuum sealer on your dried cereal might buy you a six to nine-month extension on its freshness, but it’s not the best method for long-term storage.
Some people opt to dry can their cereal and other dried goods in their mason jars. We all know this isn’t an “approved method,” but it doesn’t stop people from doing it.
Mylar bags are arguably the best way to store dried goods. They keep light, moisture, and most pests out. Plus, they’re lightweight and portable, so they’re easy to transport when needed. Just be sure to add oxygen absorbers.