The glass transition, its nature and significance in food processing

Abstract

Although the glass transition is a comparatively recent subject of study in physical science and even more so in food science, it is a phenomenon which is widely observed in natural systems. For example, the opening of the pods and the scattering of seeds by many plants relies on dehydration from a rubbery to a highly elastic and brittle glassy condition. Likewise, the formation of spiders' webs from a rubbery material that can be spun, to one which produces a robust elastic structure is the consequence of a rubber-to-glass transition. On the domestic scene, the `ironing' of a cotton sheet relies on the glass {\textrightarrow} rubber {\textrightarrow} glass transition of cellulose. There is also strong evidence that the resistance to dehydration damage and the protection against freezing temperatures observed in both animals and plants arises in many cases from transitions in the prevailing physicochemical system from rubbery to glassy states.