Molecular morphology & interactions, functional properties, rheology and in vitro digestibility of ultrasonically modified pearl millet and sorghum starches

The present research investigated to study the effect of ultrasound treatment on isolated pearl millet starch (PMS) and sorghum starch (SS). Ultrasonication was applied to PMS and SS for 10, 15, and 20 min. Ultrasonically modified pearl millet and sorghum starches evaluated for their techno-functionality, pasting profile, morphology, in vitro starch digestibility, XRD, and molecular interactions. Ultrasound treatment increased water and oil absorption capacity, swelling power, and solubility with treatment time. For ultrasonicated PMS and SS, a significant increase (p < 0.05) in paste clarity (PC) (70.05 % and 67.23 %), freeze-thawing stability (FTS), gel consistency (GC) (25.05 mm and 32.95 mm), and in vitro starch digestibility were observed (57.70 g/100 g and 50.29 g/100 g), whereas no significant changes were recorded for the color values after the ultrasound treatment. Variations in pasting property were also observed in ultrasonicated starches with treatment duration. SEM images confirmed ultrasonication mainly forms pores and indentations on starch granule surface. FTIR spectra and X-ray diffractogram for ultrasonicated starches revealed a slight decrease in the peak intensity and A-type Xray pattern with lower relative crystallinity (RC) than the native starches. G' > G value, indicating the elastic behavior and lower tan delta value, depicting viscous behavior and high gel strength.

Automated summary

The effect of ultrasound treatment on isolated pearl millet starch and sorghum starch was investigated. Ultrasound treatment increased the water and oil absorption capacity, swelling power, solubility, paste clarity, freeze-thawing stability, and gel consistency of the starches. Pores and indentations were formed on the starch granule surface after ultrasonication. Ultrasonicated starches showed lower relative crystallinity and changes in their pasting properties.