Chemistry Reference
In-Depth Information
Figure 11.15.
NMR relaxation time T
2
(a) and second moment M
2
(b) versus (T-T
g
) for freeze-
dried maltodextrins (dextrose equivalents, DE 2, 21, 40) equilibrated at a
w
¼
0.4.
T
2
represents the rotational mobility of the more mobile protons (mainly water). M
2
is considered
to be inversely related to the mobility of the less mobile protons (matrix protons
þ
possibly some
water protons) (Data from Grattard et al., 2002).
While the matrix mobility showed a significant enhancement of the tempera-
ture dependence near T
g
, for mobility of water, a continuous increase in
mobility with temperature was observed; moreover, the mobility of water
increased with the molecular weight of the matrix material (Grattard et al.,
2002). Similar conclusions can be derived from studies on water translational
diffusion (D
trans
or D
app
) (Ablett et al., 1993; Tromp et al., 1997; Aldous et al.,
1997).
