CHANGES IN THE RHEOLOGICAL PROPERTIES AND STRUCTURE OF POTATO STARCH UPON HYDROTHERMAL TREATMENT

Hydrothermal treatment carried out using a drum dryer results in pregelatinised starch. Despite the long tradition of industrial application of this method, in the scientific literature, there is a lack of detailed data on the changes in rheological properties and structure of starch subjected to hydrothermal treatment at specific processing conditions. This work is an attempt to fill this gap. Potato starch was processed at temperatures in the range of 150-170 degrees C, for 15 to 45 minutes. Obtained samples were subjected to rheometric as well as size exclusion chromatography with triple detection studies. It was stated that drum drying and oven drying processes caused similar structural changes in starch. They consist of hydrolysis accompanied by transglycosidation. As a result of these reactions, more amylose molecules and amylopectin molecules of higher molecular mass than in native starch were formed. Nevertheless drum-dried and oven-dried samples differed from each other in rheological properties which is related to some differences in their structure. Drum-dried starch had lower viscosity as it contained more compact amylopectin molecules. The conformation of molecules in oven-dried starches was similar to native starch, therefore oven-dried and native starches had higher viscosity than drum-dried starch because their amylopectin molecules adopted looser conformation than that of drum-dried samples.