Abstract:

In this research, corn resistant starch was produced by autoclaving treatment combined with psychrophilic
pullulanase hydrolysis, and starch slurry content, the amounts of heat α-amylase and psychrophilic pullulanase, and
psychrophilic pullulanase reaction time were optimized for the enhanced production of corn resistant starch through
orthogonal array experiments. Then, the crystal structure characterization and formation mechanisms of resistant starch
were investigated by using the scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning
calorimeter (DSC). It was found that the optimum parameters for resistant starch preparation were as follows: corn
starch slurry concentration, 18%; thermostable alpha-amylase dosage, 7 U/g; psychrophilic-pullulanase dosage, 10 U/g; and
reaction time, 9 h. The yield of resistant starch was 16.84% under these conditions. The crystal structure of resistant starch
belonged to the V-type, which was different from that the A-type crystal structure of raw starch. Compared to raw starch,
the resistant starch showed higher phase onset temperature (117.07 ℃), peak temperature (140.69 ℃), end temperature
(153.03 ℃) and phase change enthalpy (1 858.12 J/g), respectively, resulting in better thermo stability.

Key words: starch, pullulanase, optimization, resistant starch, crystal structure