Characterization of free radicals mechanically and thermally induced in potato starch

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.