Effect of thermal modifications of potato starch on its selected properties

Aqueous suspensions prepared from native potato starch (with the concentration 4 g/100 g) were heated to temperatures of 59, 64, 69, 74, 79, 84, 89 or 94 degrees C, under continuous stirring. The resultant solutions were cooled, frozen and defrosted, and subjected to analyses. The heating and freezing of a potato starch suspension changed its properties, with the direction and extent of these changes depending on the temperature of pre-heating. The re-pasting of the produced starch preparations in a Brabender viscosimeter increased their viscosity to 50% compared to the pastes produced from native starch. The assayed viscosity of the pastes depended on the pre-heating temperature and was changing following the determined second degree polynomial function. The thermal characteristics (DSC) of the analyzed preparations revealed peaks that corresponded to transitions of native starch pasting and retrograded starch solubilization. The strength of the produced gels, determined with the use of an oscillatory-rotational rheometer, was greater than that of gels produced from native starch and depended on the pre-heating temperature, however these changes followed the determined second order polynomial function. Microscope preparations (SEM) of retrograded starch differed significantly in porosity that was also found to depend on the pre-heating temperature. Paste viscosity was positively correlated with the size of gel sacks determined with a laser particle size analyzer (LSA). (C) 2014 Elsevier Ltd. All rights reserved.