The optimization of isoamylase processing conditions for the preparation of high-amylose ginkgo starch

A high-amylose starch was prepared from ginkgo by hydrolysis using isoamylase and its structures (morphology and crystallinity) and physicochemical properties (swelling factor, water solubility and gelatinization) were determined. The experiments used response surface methodology to determine the optimum parameters for enzymatic hydrolysis: pH 5.0 at 52 °C for 170 min, using an enzyme dose greater than 100 IU/ml. The experimentally observed maximum yield of ginkgo amylose under these conditions was 74.74% and the blue value was 0.756. The high-amylose ginkgo starch showed an irregular surface and porous inner structure while the native starch granules were oval with a smooth surface. X-ray showed that the high-amylose starch displayed a V-type structure. Because of its high amylose content and different structural characteristics, high-amylose starch exhibited a higher gelatinization peak temperature (109.25 °C) and water solubility, and a lower crystallinity (19.13%), gelatinization enthalpy (63.83 J/g), and swelling power. The present study has indicated that high-amylose starch prepared using isoamylase has unique functional properties, which lays the foundation for the wider application of ginkgo starch.