3.3. Oscillatory dynamic rheology
Dynamic rheology is useful in determining chemical characteristics
of surimi during thermal gelation that result in the development
of final texture in surimi gels (Hamann & MacDonald, 1992).
Surimi gelation occurs in two steps: (1) initiation characterised by
unfolding of protein molecules, and (2) protein aggregation resulting
in gel formation via disulfide bonds as well as hydrogen, electrostatic,
and hydrophobic interactions. Step (2) usually occurs
above 55 C and corresponds to the beginning of intermolecular disulfide bonding. Most of disulfide bonds set at mid 70 C in Alaska
pollock and Pacific whiting surimi (Yoon, Gunasekaran, & Park,
2004). Dynamic rheology was used in the present study to measure
elastic modulus (G0) in order to study the effects of individual additives
(fibre or oil) and their combination (fibre + oil) on surimi
gelation in relation to textural properties of surimi gels. The G0
curves showed typical gelation pattern for surimi, increasing rapidly
above 50 C and continuing until 90 C (Fig. 4). The G0 for surimi
containing added oil started the increase at about 55 C.
However, the extent and rate (slope) of the G0 increase as well as
the final G0 were very different between treatments. Although both
individual treatments of either fibre or oil resulted in increased G0 ,
the fibre + oil treatment had a much greater extent and rate of the
increase as well as much higher final G0 . This suggests synergistic
interaction between fibre, x-3 oil, and surimi myofibrillar proteins,
which resulted in enhanced gelation.