Retrogradation property of starch nanoparticles prepared by pullulanase and recrystallization

Retrogradation behavior of starch nanoparticles (SNPs) prepared by the recrystallization of short-chain amylose (SCA) debranched from amylopectin-rich waxy proso millet starch was investigated. In differential scanning calorimetry thermograms, the SCA: water ratio of 1: 2 (w/w) led to a remarkable increase in enthalpy at 4 or 25 degrees C compared with that corresponding to the ratios of 1: 1 and 1: 5, indicating better recrystallization and higher crystallinity of SCA. Morphology analysis showed that nanoparticles measuring 10-30 nm in diameter were formed when SCA solution (1: 5, w/v) was retrograded for 15, 30, and 60 min. As the retrogradation duration was increased to 120 and 240 min, larger SNPs appeared. X-ray diffraction patterns of all SNPs were of the B-type, and the degree of crystallinity increased when retrogradation time was prolonged.