Staling, or "going stale" (the verb to stale is used in the food industry), is a chemical and physical process in bread and other foods that reduces their palatability. Stale bread is dry and leathery.
Mechanism and effects
Staling is not, as is commonly believed, simply a drying-out process due to evaporation. Bread will stale even in a moist environment, and stales most rapidly at temperatures just above freezing. Bread stored in the refrigerator will have increased staling rates and should therefore be kept at room temperature. However, refrigeration delays the growth of mold and extends the shelf life of bread.
One important mechanism is the migration of moisture from the starch granules into the interstitial spaces, degelatinizing the starch. The starch amylose and amylopectin molecules realign themselves causing recrystalisation. This results in stale bread's leathery, hard texture. Additionally, pleasant "fresh" flavor is lost to the air, and often unpleasant flavor is absorbed from it as well, especially in a confined space with other food such as a refrigerator.
Specifically stale bread is an important ingredient in many dishes, some of which were invented for the express purpose of using up otherwise unpalatable stale bread. Examples include bread pudding, bread sauce, bread soup, skordalia, garbure, fondue, fattoush, croutons, haslet, gazpacho, wodzionka, french toast, bread dumplings and flummadiddle.
Stale bread can be partially destaled by heating to 60 °C (140 °F) in a conventional oven or microwave oven. However, if not eaten before it cools or dries, the bread is even worse than before due to the moisture loss.
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- Gray, J.A.; Bemiller, J.N. (January 2003), "Bread Staling: Molecular Basis and Control", Comprehensive Reviews in Food Science and Food Safety 2 (1): 1–21, doi:10.1111/j.1541-4337.2003.tb00011.x
- Xie, Feng (1998). The study of bread staling using visible and near-infrared reflectance spectroscopy (PDF) (Ph.D.). Kansas State University. Retrieved 2014-08-25.