Formation of free radicals due to mechanical crushing of potato starch granules in ethanol
suspension has been investigated. Nature of the radicals, their quantity, as well as the storage
and thermal stability were characterized by the electron paramagnetic resonance (EPR) spec-
troscopy aided by computer simulations. Room temperature EPR spectra obtained after starch
milling indicated that the radical species were present in the system in the quantity positively
correlated with the level of the starch granule damage dependent on the processing duration. The
product species could be assigned to the carbon type radicals formed by mechanically induced
a
-
1,4-glucosidic bond cleavage of the starch polysaccharides followed by a hydrogen abstraction
from the glucose units. Mechanically fractured starch granules were vulnerable for the thermal
treatment. Heating in the temperature range of 180–230
8
C resulted in more intense formation of
thermally generated radicals in comparison to the native starch and non-heated milled starch.
Storage stability of the radicals depended on the level of the granule destruction implying various
ways of the radical annihilation. In addition, the kinetic data of the process are presented and the
inter-radical transformations causing unexpected growth of the amount of thermally generated
radicals at the initial stage of the starch storing are discussed.
keywords in English:
deteriorated starch structure, EPR spectroscop, polysaccharide radicals, mechanolysis of starch