greater increase observed at a higher annealing temperature. No
significant changes were noted in enthalpy change of potato starch
before and after annealing. Freeze-dried potato starches showed
lower gelatinization temperatures and enthalpy change compared
with the corresponding ethanol-dehydrated starches, indicating
that freeze-drying caused a disruption to the crystalline structure of
potato starch.
3.5. Pasting properties
The pasting properties of native and annealed starches are
shown in Fig. 3. Annealing at 30 and 40 C increased greatly the
whole paste viscosity and decreased slightly the pasting temperature
of wheat starch, and the treatment at 40 C showed a greater
effect. However, annealing at 50 C reduced the overall paste viscosity
and increased the pasting temperature significantly (Fig. 3a).
Annealing treatments increased final and setback viscosities and
decreased breakdown viscosity of yam starch. The peak viscosity
was increased slightly after annealing at 30 C, but decreased after
annealing at 40 and 50 C. The trough viscosity was decreased after
annealing at 50 C, but increased after annealing at 30 and 40 C.
The pasting temperature was little affected by annealing treatment
(Fig. 3b). Annealing at 30 C had a small effect on overall pasting
profiles of potato starch. However, the treatment at 40 C increased
trough, final and setback viscosities and pasting temperature, but