Changes in maximum stress values during storage (day 0 vs.
day 7) obtained with the Instron are shown in Fig. 1 for all soy
breads. Firmness measurement of baked goods often resulted in
high standard deviation due to the inherent variability of these
food systems (Vodovotz, Baik, Vittadini, & Chinachoti, 2001).
The maximum change in firming was observed for SSF (formulation
3; 0.013 ± 0.007 MPa) followed by control soy bread (formulation
2; 0.010 ± 0.003 MPa) and ISSF breads (formulation 4;
0.010 ± 0.008 MPa), while the minimum change was for SMP (formulation
1; 0.005 ± 0.008 MPa) and SPI2 breads (formulation 7;
0.009 ± 0.006 MPa). At the end of storage SSF bread (formulation
3) had the lowest firmness (0.010 ± 0.018 MPa), whereas SPI1
(formulation 5) had the highest (0.010 ± 0.032 MPa). Brewer,
Potter, Sprouls, and Reinhard (1992) also found that higher soy
protein content increased toughness of breads. On the other hand,
SSF addition (formulation 3) resulted in softer soy breads after
7 days of storage similar to the findings by Kim and Moon
(1999) for soymilk residue extract (high in soluble dietary fibre)