Single and Dual Modification of Amaranth Starch by Ultrasound and Citric Acid: Effect of Levels for Single Modification and Sequence for Dual Modification

In this study, the effects of single and dual modification of amaranth starch by ultrasound and citric acid were studied, and the properties of modified starches were investigated. Two different levels of ultrasonication (10 and 20 min) and citric acid (10 and 20%) were used in different combinations. The levels having better properties were chosen for dual modification. Further, the effect of altering the sequence of dual modification was also investigated. The results indicated that the dual-modified starches have the highest solubility and reduced swelling power along with improved pasting and rheological properties. Freeze–thaw stability was higher for dual-modified starches, and amylose content increased upon modification. Relative crystallinity of starch samples reduced upon modification, and the gelatinization enthalpy reduced. Altering the sequence of modification affected starch properties. The smallest particle size diameter was seen in dual-modified starches. The SDS and RS content of dual-modified starches were higher in comparison with single-modified and native starches. Hence, dual-modified starches have more desirable properties compared to native starches.