Mechanism of instantaneous recrystallization in linear dextrins with various chain lengths from debranched high-amylose maize starch

This study implemented a combined approach of pullulanase debranching and gradient ethanol precipitation to rapidly develop recrystallized starch with high resistance to amylase. With the ethanol concentration increased, the morphology transformed from amorphous aggregates (Et0%, EtX% represents the precipitate obtained under X% ethanol treatment) to spherical structures (Et40% and Et50%) and stacking crystalline layer (Et60% and Et70%). This process was accompanied by a decrease in the average degree of polymerization of the sample, and the relative crystallinity of recrystallized starch increased from 10.34% to 45.97%. Notably, Et60% and Et70% groups exhibited an A-type crystalline structure, in sharp contrast to the B-type crystal observed in the other groups. This was likely because shorter chains were precipitated under high-concentration ethanol, which subsequently formed more dense monoclinic crystals. Importantly, Et70% group demonstrated 26.42% increase in resistant starch content compared with the debranched starch, which may be attributable to its more ordered crystalline structure.