Typical results of TRA measurement for trehalose cookie samples
are shown in Fig. 3. In order to avoid overlap of the data,
aw = 0.110, 0.225, and 0.328 were shifted upward by 0.75 MPa,
0.5 MPa, and 0.25 MPa, respectively. The samples showed a drastic
decrease in mechanical stress above a certain temperature, and
then Ts value could be determined from the onset point. It is noted
that Ts decreased with increasing aw of samples because of water
plasticising. There was a small decrease in the mechanical stress
in the temperature range between 20 C and 30 C, attributable
to the melting of fat (Ma, 1990; Roos, 1995). The mechanical stress
increased gradually with increasing temperature, at temperatures
above 40 C, because of thermal expansion (Chang & Randall,
1992).