Characterization of free radicals mechanically and thermally induced in potato starch

Abstract

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) spectroscopy 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 180-2308C 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.

Photochemical Reactions in Dialdehyde Starch

“…The most noticeable changes occur in the range of the hydroxyl bond vibrations, which is initially associated with the loss of absorbed water, and then, with the abstraction of OH groups from the macromolecules. The primary photochemical processes, due to homolytic cleavage of chemical bonds, lead to formation of free radicals, which were repeatedly detected in starch with ESR [27,28,29]. These radicals, owing to their high activity, are capable of taking part in secondary reactions, which usually result in creation of complex mixture of degradation products.…”