Native potato starch was suspended in distilled water at starch: water ratio of 1:3 (w/v). The
starch-water suspensions were then subjected to repeated annealing treatments (RANN) at
55 °C for 12 h, repeated for 8 cycles or continuous annealing treatments (CANN) at 55 °C for
24, 48, 72 and 96 h. The structural, physiochemical and digestive properties of the annealed
starch samples were studied and compared with those of the native starch. The scanning
electron microscopy and light microscopy analysis showed that the repeated and continuous
annealing treatments could keep the integrity and surface perfection of the starch granules.
The growth rings of the annealed starch granules were more distinct than those of the native
starch granules as revealed by confocal laser scanning microscopy. The crystallinity degree
increased and the crystalline retained the B-type pattern after the annealing treatments. There
were no chemical bonds and functional groups produced or disappeared during the applied
annealing treatments. Infrared absorption peak intensity of starch decreased and short-range
ordered structures increased after treatments. The swelling power and solubility decreased at
low temperature (50 to 60 oC) and increased at relatively high temperature (70 to 90 oC). The
rapid visco-analyzer and differential scanning calorimeter analysis revealed an increase in the
setback, final viscosity, pasting temperature and gelatinization transition temperature, and a
decrease in breakdown value of the starch after the annealing treatments. On the other hand,
the repeated and continuous annealing treatments resulted in starch with low in vitro
digestibility degree, indicating formation of resistant starch. Generally, the repeated annealing
treatment resulted in starch with high improved properties compared with the starch resulted
from the continuous annealing treatments. Therefore, the repeated annealing treatments can be
suggested as an effective method for producing of modified starch for food industrial
applications.