In the oven: Preheat oven to 200° or Warm setting. Wrap the bread in a damp (not soaking) towel, place on a baking sheet, and pop it in the oven for 5-10 minutes. In the microwave: Wrap the bread in a damp (not soaking) towel, place it on a microwave-safe dish, and microwave on high for 10 seconds.
“Take your bread, and run it under a tap, or immerse it completely in water,” says Cher Loh, Head Tutor at the Good Housekeeping Institute Cookery School. “This rehydrates the bread.” "Then stick it in the oven at 200°C (180°C fan) for a few minutes, and your bread will miraculously be edible once more."
Don't want to deal with the stove? You can revive stale bread in the microwave, too. Just wrap the loaf in a damp towel and microwave on high for 10 seconds. After that, you're good to go.
In microwave heating, the starch of the bread is re-gelatinised. That is to say, the starch molecules bind to water molecules, which sort of dissolve or plasticise the starch, making the texture of the bread softer overall. One of the properties of microwaves is that they are absorbed by water.
This is the approach The Spruce Eats recommends for bringing back stale bread — dampen under the faucet, wrap the whole loaf in foil, and reheat for 15 minutes in a 300°F oven.
Simply drench your rock-hard baguette in cold water then tightly wrap it in aluminum foil. Next, place the wrapped baguette in the oven (not preheated), then set the temperature to 300°F and let is heat for 12 to 15 minutes.
Microwave. An excellent way to reheat bread is to place the container and line it with two layers of paper towels. Like what we did in the oven, we will wrap the bread with a damp towel. Heat the bread for ten seconds on a low setting.
In the oven: Preheat oven to 200° or Warm setting. Wrap the bread in a damp (not soaking) towel, place on a baking sheet, and pop it in the oven for 5-10 minutes. In the microwave: Wrap the bread in a damp (not soaking) towel, place it on a microwave-safe dish, and microwave on high for 10 seconds.
If you want to make stale bread soft again, wrap the bread in foil. If the crust of the bread is very hard, sprinkle a little water on the outside before you close the foil. Place the bread in a 300°F oven for 5-15 minutes or until the bread feels soft.
As bread starts to cool, however, water leaves the starch and moves into other parts of the mixture, allowing starch molecules to return to their crystallized state. It's this recrystallization – not drying – that makes bread go hard, and it happens even in humid conditions.
Stale bread is still edible, but moldy bread is not. If there is any visible molding on the loaf, you will need to throw it out. You don't want to get sick from eating old food.
Commercial bakeries use two types of ingredients to slow spoilage — emulsifiers and enzymes. Emulsifiers keep bread from going stale by preventing oil and water from separating. Adding emulsifiers sometimes goes by the names “crumb softening” or “dough conditioning” because it works to preserve texture.
When one of those sugar molecules reaches 212 degrees Fahrenheit, it melts, which softens it. This is why bread can actually feel soft and fluffy when it first comes out of the microwave. But then when it cools, that molecule recrystallizes and hardens, causing the bread to become chewy and hard.
The reason a refrigerator is bad for bread: When bread is stored in a cold (but above freezing) environment, this recrystallization, and therefore staling, happens much faster than at warmer temperatures. Freezing, however, dramatically slows the process down. So that's the science in a nutshell.
The browning is the result of a Maillard reaction altering the flavor of the bread and making it firmer. The firm surface is easier to spread toppings on and the warmth can help butter reach its melting point. Toasting is a common method of making stale bread more palatable.