Most fresh bread is made with just the four basic ingredients of flour, yeast, water, and salt, yet the simple combination makes for a delicious snack with a delightfully light, airy center. However, once bread has gone stale, it’s practically inedible — but why is this?

Whenever something goes stale, it is generally the result of exposure to air over time, which causes the food item to lose moisture. When water is added during the baking process, it weakens the shape of the starch molecules and allows them to retain more water, but this process is reversed when bread is left in open air.

Keeping bread sealed to minimize its exposure to air can help reduce the moisture loss that makes bread go stale, keeping it fresher. Bread can also be stored in the freezer for up to two months without becoming stale and hard, though putting it in the refrigerator instead will make it go stale quicker.