Starch molecules tend to crystallize slowly, and when water is needed, gluten becomes hard when it loses water. Answer expert: The process of bread hardening by James BeMiller, emeritus professor of food science at Purdue University in the United States, has not been fully explained. Although the crystallization of starch polymer molecules has been unanimously recognized, it is not the only factor that works. As soon as the bread left the oven and began to cool, it began to harden. The speed of bread hardening depends on its composition, baking process and storage conditions. Bread is a spongy network composed of starch molecules and protein molecules of wheat flour called gluten. These cells are filled with carbon dioxide gas produced by yeast during fermentation. Over time, these starch molecules tend to crystallize. Starch crystals are different from crystals of sugar or salt, which are microcrystals formed in small areas of starch polymer macromolecules. Water is essential for the formation of these microcrystals, and starch will absorb the required water molecules from gluten. When gluten loses moisture, it changes from a rubbery state to a hard state (so-called glassy state), which makes bread hard. But if you heat the hardened bread, it will change from hard to soft, and the bread will become soft and delicious. Copyright belongs to the author, and no one may reprint or use all or any part of it without the written permission of the author. Print recipes