D. Champion et al., Towards an improved understanding of glass transition and relaxations in foods: molecular mobility in the glass transition range, TRENDS FOOD, 11(2), 2000, pp. 41-55
Recent research ha's contributed to a better understanding of the glass-liq
uid transition (GLT) and its relationship with relaxation processes in the.
material. This paper reviews models and theories that are currently used t
o describe and explain the physical changes in the GLT temperature range (T
-g); ageing below T-g, changes in mechanical properties above T-g, and the
concept of fragility are described. Measurements of the GLT temperature are
now practised routinely in many food laboratories, but lack of information
on the experimental conditions may lead to discrepancies between results.
Several examples from the food domain are reported, illustrating that the G
LT has been mainly used to interpret, with more or less success, changes in
low moisture foods and biomaterials. Taking the temperature of GLT into co
nsideration alone cannot sufficiently explain changes as a function of temp
erature or water content, particularly when chemical/biochemical reactions
are concerned. The relationship between molecular mobility and the GLT is d
iscussed. More measurements of the various types of molecular motions are n
ecessary, specialty in close vicinity to the GLT and in the glassy state. (
C) 2000 Elsevier Science Ltd. All rights reserved.