When NaCl and SPI were added, there was an increased trend for gel strength of konjac/κ-
carrageenan and konjac/gellan mixed gels with increasing of NaCl concentration while a
decrease in gel strength of konjac/xanthan mixed gels was occurred as NaCl concentration
was increased. Increasing NaCl levels enhanced the gel strength of konjac/κ-carrageenan or
gellan gum mixed gels, possibly due to more ionic and hydrogen bonds formed between
konjac molecules as a result of the ionic atmosphere, with an excess of ions of the charge
opposite to that of anionic polysaccharides (κ-carrageenan and gellan gum), decrease the
electrostatic free energy of the sysetm [9]. This result was in agreement with the work of
Totosaus et al. [6], who showed that the gel strengths of gum-protein mixtures including
gellan, κ-carrageenan, bovine serum albumin and egg white albumin were dependent upon
the concentration and type of monovalent cation, resulting in strong gels with potassium ion
than sodium ion.
As shown in Table 2, the addition of SPI significantly affected (p < 0.05) only the gel
strength of konjac/κ-carrageenan mixed gel when gelated in no added NaCl condition;
nevertheless, it showed no significant effect (p > 0.05) when NaCl was incorporated up to 1%
level. The mixed gels between konjac flour and xanthan or gellan gum, with or without added
NaCl, showed no significant differences (p > 0.05) in gel strengths at any levels of SPI
addition. This was attributed to the interactions of konjac flour and xanthan or gellan
produced heat-induced mixed gels with higher gel hardness than that with κ-carrageenan
(Table 3), resulting in the rigid conformational structure or stronger network strength which
hindered interactions between konjac flour and SPI [10].