Staling

Though staling seems to involve the loss of moisture as the bread becomes dry, hard, and crumbly, it is more of an effect of starch retrogradation than net water loss. In 1852, Frenchman Jean Baptiste Boussingault conducted an experiment where bread was hermetically sealed to prevent moisture loss, yet it still became stale. Staling is now understood to be a manifestation of recrystallization and water migration out of the starch granules into the surrounding gluten network. The retrogradation of simple amylsoe molecules leads to the hardening of the bread. Branched amylopectins also retrograde, but do so more slowly. Certain emulsifying agents have been found to retard staling substantially. Manufacturers have added these to mass-produced bread dough for the last 50 years. True buttermilk and eggs have the same effects.

As long as the loaf is not too old, or has been refrigerated, staling can be reversed by reheating the bread above the gelation temperature of starch, 140 degrees F/60 degrees C. Toasting makes the interior of bread soft. A loaf of bread can be refreshed by heating in the oven.

Refrigerating bread can speed up the staling process by as much as 6 days! If bread is to be used in a couple of days, it is best to store at room temperature in a bread box or paper bag to reduce moisture loss. If bread is to be kept longer, it is best to wrap it in plastic or foil, and freeze it. Refrigerate bread only if it is to be toasted or reheated before consumption.

Bread tends to dry out before becoming spoiled. Still, bread that is kept at room temperature in a plastic bag allows moiture from the staling starch granules to collect on bread surfaces. The most commonly found toxic molds in spoiled bread are Aspergillus, Penicillium, Mucor, and Monilia sitophila.