temperatures are due to the increasing number of chemical junctions
responsible for the formation of the amide bonds (Saito et al.,
2007). Yan et al. (2011) reported that gelatin gels from walleye
pollock skin added with gallic acid (10e40 mg g1) and rutin
(2e8 mg g1) had gelling temperature of 4e6 C and the melting
temperature of 11e13 C. Therefore, the addition of EECH at an
appropriate level could increase gelling point, in which gel could be
formed easier than the control. Also gelwas maintained for a longer
time as indicated by the higher melting temperature. Generally, the
melting point was higher than the gelling point because gelatin gel
absorbed energy when it was melting (Liu, Li, & Guo, 2008).
3.3.2. Microstructure of gelatin gels
Microstructures of gels of swim bladder gelatins without
EECH (A) and those added with EECH at levels of 0.5 mg g1 dry
gelatin (B) and 5 mg g1 dry gelatin (C) are illustrated in Fig. 5.
All gelatin gels were sponge or coral-like in structure. Generally,
the arrangement and association of protein molecules in the gel
matrix directly contributed to the gel strength of the gelatin
(Benjakul et al., 2009). The control gel showed the finest gel
network with very small voids. When EECH at 0.5 mg g1 was
incorporated, the uniform structure with larger strands was
formed. This was coincidental with the increase in gel strength
(Fig. 2). However, non-uniform structure with disconnected large
strands and large voids was obtained as EECH at 5 mg g1 was
present. Gelatin could undergo the coagulation more effectively
in the presence of EECH at an excessive amount. The coagulated
gelatin chains could not undergo the gelation with the ordered