What is the principle behind cookies becoming brittle after being damp and stored in the refrigerator

Storing cookies in the refrigerator after being damp can restore their crispness, mainly due to water evaporation and starch retrogradation. After the cookies become damp, the moisture is absorbed, causing them to become soft. After being placed in the refrigerator, the low temperature environment promotes the evaporation of moisture, while starch molecules rearrange to form a brittle structure. The main components of cookies are flour, sugar, and oil, with flour containing a large amount of starch. When cookies are exposed to a humid environment, starch absorbs moisture from the air, causing the cookies to become soft. After placing damp cookies in the refrigerator, the low temperature environment will accelerate the evaporation of moisture, reducing the moisture content inside the cookies. At the same time, starch molecules undergo retrogradation at low temperatures, rearranging to form a tighter structure, thereby restoring brittleness. The low temperature environment of the refrigerator is relatively dry, which helps to reduce the moisture content in the air. After being stored in the refrigerator for a period of time, the moisture will gradually evaporate, making the cookies crispy again. But this method is only suitable for cookies that have been slightly damp. If the cookies have been severely damp or spoiled, they cannot be restored to their original taste even if they are placed in the refrigerator.

When storing cookies in daily life, it is recommended to seal and store them in a cool and dry place to avoid moisture. If the cookies have become damp, you can try refrigerating them in the refrigerator for a while to restore their crispness, but it is not advisable to refrigerate them for a long time to avoid affecting the taste. Choosing iron or glass containers to store cookies is more moisture-proof than plastic containers, and it is recommended to consume them as soon as possible after opening to ensure the best flavor.