Abstract:

In this study, the self-assembling behavior of collagen from grass carp and snakehead skin was investigated by
applying turbidity and rheology methods. The results indicated that both turbidity curve and rheology curve of the two
collagens showed a three-stage pattern including nucleation phase, assembling phase and equilibrium phase. In turbidity
tests, the time of nucleation phase was 13.5 and 3.5 min, and the time of assembling phase was 72.6 and 10.0 min for pepsinsolubilized
collagen (PSC) from grass carp and snakehead skins, respectively. In rheology tests, the time of nucleation
phase were 6.7 and 1.9 min, and the time of assembling phase was 105 and 58 min for skin PSC from grass carp and
snakehead, respectively. Compared with the results of turbidity tests, the time of nucleation phase was shorter and the time
of assembling phase was longer according to the results of rheology tests. The collagen fiber diameter was further increased
after the equilibrium phase from turbidity tests until the equilibrium phase from rheology tests was reached, and then
remained stable, suggesting that the self-assembling behavior of collagen could be more sensitively and integrally observed
by rheology method when compared with turbidity tests. Based on the results of rheology tests, the assembling rate of
snakehead collagen was faster and the assembling collagen gel was harder than that of grass carp collagen, indicating that
self-assembling behavior among different collagens is different.

Key words: freshwater fish, collagen, self-assembly, gelation, rheology