Wheat gluten glass transition temperature

One of the questions posed in Chapter 1 was "Why does dough from cereals other than wheat not have viscoelastic properties " It is well established that the gluten proteins of wheat are responsible for the viscoelastic properties of wheat flom dough (see Chapter 6). The requirements for a protein (or any polymer) to exhibit viscoelasticity are discussed in Chapter 14. One of these is that the protein should be above its glass transition temperature (Tg). Zein, the prolamin protein of maize, is found to contribute viscoelastic properties to a zein-starch dough when the temperature is raised above its Tg at that water content (Bushuk and MacRitchie 1989 Lawton 1992). This shows that it is possible to obtain viscoelastic properties with nonwheat cereal proteins. 

Figure 1 Effect of water content on the glass transition temperature (Tf and on minimum thermosetting temperature (Tr) for wheat gluten proteins (10).

Figure 11.5 Effect of water content on the glass transition temperature (Tg) and on minimum thermosetting temperature (T ) for wheat gluten proteins. From Hoseney and co-workers [138] (O) Kalichevski and co-workers [139] ( ) Nicholls and co-workers (O) Cherian and Chinachoti [129] (A) Pouplin and co-workers [162] (X). The thermosetting temperature ( ) was determined for wheat glutenins [141]...

Figure 11.6 Schematic representation of relationships between water activity, water content, glass transition temperature and viscosity for wheat gluten based films. Calculated values were obtained by using the GAB equation [151], Couchman and Karasz equation [146] and Williams Landel and Ferry equation [128]. The critical water activity (a ) and moisture content (M ) are indicated when Tg is equal to the ambient temperature...

Figure 11.7 Schematic representation of the thermoplastic process applied to shape agro-packagings based on wheat gluten proteins in relation to the glass transition temperature (adapted from Cuq and co-workers [10])...

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