Principles of Cereal Science and Technology, Third Edition
When crisp cookies are kept in a moist environment, they loose their crispiness and become pliable. When breakfast cereals are left in milk for too long, they become soggy. To prevent bread from firming, one can store it in a household freezer at −18°C (0°F). These examples of changes in properties of cereal foods have to do with a phenomenon known as “glass transition.” While glass transition has been known for a long time as a phenomenon of synthetic polymers, scientists have understood for only about two decades that proteins and polysaccharides, as natural polymers, are also subject to glass transition. In the following sections, the phenomenon of glass transition and its significance for cereal-based food systems are described.