Effects of pullulanase pretreatment on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes

The effects of pullulanase pretreatment, combined with ultrasound-microwave synergistic processing, on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes was investigated. The pullulanase pretreatment improved the complex index of the inclusion complexes. The structural properties analysis indicated the debranching of starch by pullulanase facilitated an increase in microcrystalline regions and ordering of starch. However, extensive debranching resulted in a blend of B- and V-type crystalline structures and a high degree of freedom of amylose chains. The microstructural morphology revealed that pullulanase debranching inhibited the gelatinization of starch by promotion of V-complex formation, while excessive enzymolysis did not. The stability of starch complex structure determined its digestibility, and the digestion analysis revealed that 100 min of pullulanase debranching contributed to the high content of V-type resistant starch. After that, starch helix conformations was more inclined to imperfect amylose double helices, reflecting an increase in slowly digestible starch content.