Molecular Structure and Properties of Resistant Dextrins from Potato Starch Prepared by Microwave Heating

The dextrinization of potato starch was performed using a sophisticated single-mode microwave reactor with temperature and pressure control using 10 cycles of heating with stirring between cycles. Microwave power from 150 to 250 W, a cycle time from 15 to 25 s, and two types of vessels with different internal diameters (12 and 24 mm) and therefore different thicknesses of the heated starch layer were used in order to estimate the impact of vessel size used for microwave dextrinization. The characteristics of resistant dextrins (RD) including solubility in water, total dietary fiber (TDF) content, color parameters, the share of various glycosidic bonds, and pasting and rheological properties were carried out. The applied conditions allowed us to obtain RDs with water solubility up to 74% at 20 °C, as well as TDF content up to 47%, with a predominance of low-molecular-weight soluble fiber fraction, with increased content of non-starch glycosidic bonds, negligible viscosity, and a slightly beige color. The geometry of the reaction vessel influenced the properties of dextrins obtained under the same heating power, time, and repetition amounts. Among the conditions used, the most favorable conditions were heating 10 times for 20 s at 200 W in a 10 mL vessel and the least favorable were 15 s cycles.