Optimization of ultrasonic pre-treatment for improving the reaction activity of potato starch by response surface methodology

The potato starch was used as raw material with the starch viscosity as indicator,on the basis of single factor test,the effect of starch concentration,ultrasonic power,ultrasonic time and their interactions on the reaction activity of potato starch were investigated by response surface methodology.The results showed that the optimum process parameters were:starch concentration 29%,ultrasonic power 290 W,ultrasonic time 29min.The viscosity of starch activated under this condition was minimum,which was 10 251.8mPa·s on average,and the relative error compared with the theoretical value 10 116mPa·s was 1.34%.The degree of substitution(DS)of carboxymethyl starch(CMS)made by this activated starch under the condition of starch concentration 30%,ethanol concentration 85%,molar ratio of NaOH to starch 1.0,molar ration of ClCH2 COOH to starch 0.6,alkalization temperature 35 ℃,alkalization time 30min,etherification temperature 45℃,etherification time 90min was 0.21,which was 40% higher than the DS(0.15)of CMS made by the native starch under the same condition.These results indicate that ultrasonic pre-treatment can improve the reaction activity of carboxymethylation of potato starch.