Effect of enzymatic hydrolysis on rheological properties of potato starch and on content of resistant starch.

Granular structure of potato starch can be changed by targeted action of enzymes and temperature in the presence of large amounts of water (Annealing). As a result, starch is modified due to changes in binding force between crystalline and amorphous starch matrix. This paper discusses the reactions of commercial potato starches to amylolytic enzyme preparations (Ban, Promozym and Ban+Promozyme), their rheological properties and resistant starch (RS) content. Significant differences in the final degree of potato starch degradation were observed. The highest glucose values were determined after hydrolysis with combination of α-Amylase and Pullulanase (19%). Longer hydrolysis time and higher temperatures affected the hydrolysis rate positively. The characteristic viscosity curve of potato starches was affected by hydrothermal enzymatic treatment. Starch samples hydrolysed with α-Amylase always showed the lowest viscosities. Without enzymes and with Pullulanase annealed starch showed lower viscosity values in comparison to native starch, but much higher in comparison to starch samples modified with α-Amylase. RS content increased due to hydrothermal enzymatic modification of potato starch. The RS content of starch samples could be substantially increased by gelatinisation and subsequent retrogradation during cooling.