Structure and properties of maize starch processed with a combination of α-amylase and pullulanase

The dissolution and digestion characteristics of maize starch processed with a combination of α-amylase and pullulanase (ERS) were investigated. The results were compared with those of high pressure-processed RS (HRS) and regular maize starch. The ERS exhibited a considerably lower dissolution and digestibility than the HRS under conditions that simulated the stomach and small intestine in vitro. Infrared spectroscopy showed two bands at 1047 and 1002 cm(-1) for ERS, which suggested an easily produced RS during the retrogradation process after enzymatic treatment. High-performance size-exclusion chromatography showed a hydrolyzed ERS forming a critical molecular weight fraction (MW 4833 Da; DP 29.8). X-ray diffraction analysis also revealed a significant difference between the types of HRS (B+V type) and ERS (in the transformation from B+V to V type) crystallinities, and the crystal structure change leads to improved anti-enzymatic properties of ERS. These results indicate that the enzyme-combined method is a more promising technique than high pressure to prepare RS from maize starch with greater resistance.