Two mg of starch samples were ground and dried under an infrared lamp with 150 mg potassium bromide in an agate mortar.This removed both the free and crystalline water in the samples, so
that it could eliminate the interference of water molecules with the absorption peaks. The mashed powder was put into a vacuum compression and pressed into a sheet. Starch samples were scanned using Fourier Transform Infrared Spectrometer (AVATAR360,Nicolet Company, USA). The spectra were recorded in transmission mode from 400 to 4000 cm1 at a resolution of 4 cm1 at room temperature.