depend on pH and salt type and concentration (Bryant &
McClements, 1998). Fig. 1a indicates the surface hardness of
various heat-set SPI macrogels, taken as the peak of the force vs
distance curves. Clear breakage was not observed for almost all the
samples except for the SPI macrogels with no added salts. Fig. 1b
shows elasticity of the SPI and LMW-SPI macrogels as measured by
the slope of initial linear part of the force versus distance curves.
Even though a higher concentration of LMW-SPI (20 wt%) was used
compared to SPI (15 wt%), the SPI macrogel had a higher elasticity
than the LMW-SPI macrogel. This is probably because the LMW-SPI
consisted of partially hydrolysed proteins that were less able to
form well-organized molecules networks, with lower water holding
capacity.