Insights into the relations between the molecular structures and digestion properties of retrograded starch after ultrasonic treatment

In this study, ultrasound was used to modulate the molecular structure of retrograded starch (RS3) responsible for the digestion properties, and the relationships among the ultrasonic power, molecular structure, and RS3 digestibility were revealed. Results revealed that the morphological characteristics of RS3 changed after ultrasonic treatment, and high power resulted in more compact block-shape structure. The results of particle size analysis, Fourier transform infrared spectroscopy, and X-ray diffraction showed that ultrasound decreased the long-range orders but increased the median particle size, short-range orders, and V-type polymorph of ultrasound-treated RS3. A decreased (double helix of amylopectin) and an increased (single helix of V-amylose) enthalpy change were observed by differential scanning calorimeter. Digestion profiles showed that some fractions of rapidly-digestible starch were converted into slowly-digestible starch and/or resistant starch. This study provides a potential approach to regulate the digestion of starch-rich foods with desired digestibility through ultrasonic treatment.