How Staling Works

• As bread bakes, its starch granules swell with water, gelatinize and soften. Once the bread is removed from the oven and begins to cool, the starch granules gradually crystallize as they expel water and harden. This process, called starch retrogradation, is what causes bread to stale. Although stale bread seems dry, it hasn’t necessarily lost moisture. The water expelled by the starch granules is trapped by the surrounding gluten or crystalline structure. This is why even well-wrapped bread eventually hardens.

Fermentation and Leavening

• The type of leavening is a major factor in how fast bread stales. Bread made from fermented dough leavened with wild yeast, such as sourdough bread, has a long shelf life. The beneficial bacteria from the fermentation process, along with the acidity they produce, delay staling and also resist microbes that cause spoilage. On the other hand, quick breads stale very rapidly. Quick breads are made with chemical leavening – baking powder or baking soda – to rise instantly as they bake.

Ingredients and Emulsifiers

• Specific ingredients also affect how fast bread becomes stale. Potatoes deter wheat starches from crystallizing, keeping potato bread soft and fresh. Emulsifiers, which are agents that join different components together, help delay staling by inhibiting water movement in the bread. Mass-produced breads usually contain emulsifiers. Egg yolks are natural emulsifiers commonly present in quick breads, as well as some rich, yeasted breads such as brioche. Sugar and honey also delay staling, so sweet breads tend to keep well.

Temperature and Storage

• Although it seems logical that storing bread in the refrigerator would help preserve freshness, it actually hastens staling. Bread stales most quickly when it is stored at temperatures between 32 and 50 degrees Fahrenheit. Storing the bread in the refrigerator does help inhibit mold growth, but most breads stored at room temperature become stale before they grow mold. For longer storage, wrap the bread well and freeze it rather than keeping it in the refrigerator.

Reviving Stale Bread

• Any bread that has been properly wrapped to prevent moisture loss can be temporarily revived after it stales. Reheating the bread causes the starch granules to reabsorb the water that is trapped in the surrounding gluten or crystalline structure. Since the gelation temperature of wheat starch is 140 F, the bread’s interior must reach that temperature to reverse staling. After the bread cools once more, it should be eaten immediately because it rapidly becomes stale again.