Glass Transition and State Diagram of Food
The physical state and physicochemical properties of food components affect food behaviour in processing and storage. Many of the food components can exist in the amorphous state, especially at low temperatures, and/or low moisture contents. Amorphous materials may exist in a solid-like, glassy state, or in a viscous or rubbery state. Glasses are formed when a liquid or a rubbery system is cooled so rapidly that there is no time for the molecules to rearrange themselves and pack into crystalline domains. With continued cooling, the system exhibits a significant change in thermal, mechanical, and other physical properties at the glass transition region.
Phase Transitions occuring in food component
Applications of Glassy State Concept in Food Systems
-A low glass transition: at room/mouth temperature, the food is soft and relatively elastic, and at higher temperatures it may even flow.
-A food with a high glass transition temperature is hard and brittle at ambient temperature.
•Texture and Structure
Lost of crispy structure if the moisture content of crispy products increases.
•Crystallization
Temperatures above glass allow molecular mobility and rearrangement of molecules to the crystalline state.
•Stickiness
Initiation of viscous flow, caking, and stickiness depends on the glass transition temperature.
Additional reading materials:
-A low glass transition: at room/mouth temperature, the food is soft and relatively elastic, and at higher temperatures it may even flow.
-A food with a high glass transition temperature is hard and brittle at ambient temperature.
•Texture and Structure
Lost of crispy structure if the moisture content of crispy products increases.
•Crystallization
Temperatures above glass allow molecular mobility and rearrangement of molecules to the crystalline state.
•Stickiness
Initiation of viscous flow, caking, and stickiness depends on the glass transition temperature.
Additional reading materials:
| Glass transition and state diagram of foods |
