Abstract: The preparation of dialdehyde starch (DAS) from mung bean starch was achieved by homogeneous sodium periodate oxidation. The effects of pre-treatment temperature, enzymatic treatment, ultrasonic activation in the pre-treatment stage and reaction temperature, reaction time, pH, sodium periodate/starch ratio and phase transfer catalysts in the oxidation stage on the preparation of dialdehyde were investigated. Ultrasonic activation and phase transfer catalysis were first studied in this study. Orthogonal test was applied to explore the optimal preparation conditions of DAS. Results indicated that ultrasonic activation of starch at 30 ℃ for 30 min was beneficial to improve reaction activation and the application of enzyme was not suitable in the pre-treatment stage. The optimal pre-treatment temperature was 50－60 ℃. In addition, phase transfer catalysis was also beneficial to improve the content of aldehyde group in final products. The optimal experiment conditions were cetyltrimethyl ammonium chloride (CETAC) as the phase transfer catalyst, reaction temperature of 40 ℃, reaction time of 2 h, pH 2, NaIO4/starch ratio of 1.0:1.0, NaIO4 concentration of 0.5 mol/L, and starch concentration of 10%. The obtained final products were white and the content of aldehyde group in final products was up to 96.81%. The spectral and physicochemical properties of DAS were consistent with previous reports.

Key words: starch, homogeneous, NaIO4 oxidation, ultrasonic activation, phase transfer catalyst, preparation, dialdehyde starch