Effect of Ultrasound Combined with Freeze-Thaw Cycles on the Pasting Properties of Pea Starch and Its Mechanism

This study investigated the effects and mechanisms of ultrasound (UT), freeze-thaw cycles (FTT1, FTT4, and FTT8 representing 1, 4, and 8 cycles, respectively), and their sequential combination (UT-FTT and FTT-UT) on the pasting properties of pea starch. The results showed that all treatments except UT alone caused the surface of starch granules to become rough and form indentations, with the combined treatments leading to partial breakage of starch granules. All treatments did not change the C-type crystal structure of pea starch, but reduced its relative crystallinity, short-range molecular order, and crystalline lamella thickness. UT-FTT1 more significantly reduced the amylose content, molecular molar mass, and the proportion of long chains of amylopectin compared with the other treatments. This was attributed to the depolymerization and rearrangement of amylopectin chains induced by ultrasonic cavitation, which enhanced the ordered breakage of starch chains from the amorphous region to the crystalline region of the granules caused by the mechanical force of ice crystals during the subsequent freeze-thaw cycles. The breakdown and setback values of pea starch were 1300.0 and 3622.0 cP and decreased to 952.3 and 2913.7 cP after UT-FTT1, respectively (P < 0.05). This indicates that UT-FTT effectively improves the thermal paste stability and anti-retrogradation ability of pea starch. This study provides new insights for the efficient regulation of starch pasting properties.