Preparation Of Ultrasonic-Oxidized Potato Starch And Its Structure And Properties

Potato starch has great application potential,but its properties such as high viscosity,and easy to retrograde limit its application.As a common modification method of starch,oxidation treatment can greatly improve the properties of starch.As a new physical modification method,ultrasonic treatment has been paid more and more attention.In this study,potato starch was oxidized with the aid of ultrasonic treatment.The effect of reaction conditions on the oxidation degree of potato starch was studied,and the optimal process parameters were determined to optimize the preparation process of ultrasonic-oxidized potato starch,meanwhile,its structure and physicochemical properties were studied.The main contents and results are as follows:The effects of different reaction time,reaction p H,reaction temperature,addition amount of hydrogen peroxide,addition amount of ferrous sulfate,ultrasonic frequency and ultrasonic power on the oxidation degree of potato starch were studied.Orthogonal test was designed to determine the optimum technological parameters.The results showed that the oxidation rate and the degree of starch oxidation could be significantly increased by ultrasonic treatment.The optimum reaction conditions were determined that p H=5,temperature was 45℃,reaction time was 90min,addition amount of hydrogen peroxide was 15%,addition amount of ferrous sulfate was 0.05%,ultrasonic power was 550W,ultrasonic frequency was 25+80k Hz.The carboxyl content of oxidized potato starch reached 0.4561%by this process.The morphological structure of original starch,ultrasonic starch,oxidized starch and ultrasonic-oxidized starch were studied.SEM images showed that the particles of modified starch were damaged to different degrees,and the grain diameter was smaller.The ultrasonic oxidation starch particles were the most damaged.XRD results showed that the crystal type of modified starch did not change,but the crystallinity decreased.The crystallinity of original starch was the highest（23.54%）,and ultrasonic-oxidized starch was the lowest（9.99%）.FTIR showed that a new absorption peak appeared near 1734 cm^-1,which confirmed the formation of carboxyl groups in the oxidation reaction.The short-range order of modified starch increased,which indicated that the damage of ultrasonic and oxidation reaction mainly occurred in the amorphous region.The physicochemical properties of original starch and modified starch were analyzed.Compared with the original starch,the peak viscosity of ultrasonic starch,oxidized starch and ultrasonic-oxidized starch decreased by 43.77%,56.98%and 77.15%respectively,the thermal stability and anti-retrogradation ability were improved.DSC analysis showed that the initial gelatinization temperature（T_o）and the peak temperature T_pof ultrasonic-oxidized starch increased,while the gelatinization enthalpy decreased.Meanwhile,ultrasonic-oxidized starch had the highest solubility（2.56%higher than original starch）,paste transparency（19.97%higher than original starch）,the freeze-thaw stability and retrogradation were improved.