Study On Preparation And Properties Of Crosslingking Carboxymethyl Starch

In this paper, the preparation and properties of wheat carboxymethyl starch, wheat crosslingking starch and crosslingking carboxymethl compound starch were studied. The aim is to prepare compound modified starch and to increase the value ofthe wheat starch.The carboxymethyl starch was produced with wheat starch by the wet process, which was prepared by chloroactic acid and sodium hydroxide. We studied the different factors in preparation on degree of substitution (DS) of carboxymethyl starch, which include the dosage of chloroactic acid , the dosage of sodium hydroxide, the concentration of ethanol, the reaction temperature and the reaction time. On the basis of one-factor experiments, we select the ration of starch, chloroactic acid and sodium hydroxide, the concentration of ethanol, the reaction temperature and the reaction time as the variables, DS as the experiment index, using L₉ (3⁴) orthogonal experiment, we can obtain the following optimum processing conditions for preparation srarch: chloroactic acid: sodium hydroxide= 1:1:2.0, the congcention of ethanol was 95%, reaction temperature was 45 ℃, reaction time was 3.0h, the DS of final products were about 0.76. The past properties of wheat carboxymethl starch have been studied, the result indicated that the wheat carboxymethyl starch has fine properties of freeze-thaw stability,higher clarity,strong anti-mycotic and anti-retrogradation characteristics.The stability of hot paste viscosity decreased and the cold paste viscosity increased.The sodium have shown better effects on the paste viscosity.The wheat crosslingking starch was prepared by POCl₃ and sodium hydroxide. The effect factors on degree of crosslingking were studied ,which included reaction time, pH value, reaction temperature and the dosage of POCl₃3 . we studied the propertie of the wheat crosslingking starch, the result indicated that the wheat crosslingking starch has fine properties of freeze-thaw stability, strong anti-cutting and etc.The crosslingking carboxymethyl starch was produced by the carboxymethyl starch and the crosslingking starch. We studied the different factors in preparation on degree of substitution (DS₁) of CCMS, which include the dosage of chloroactic acid , the dosage of sodium hydroxide, the concentration of ethanol, the reaction temperature and the reaction time. As a result ,the degree of crosslingking play a unimportant role on DS₁, so we select the dosage of chloroactic acid , the dosage of sodium hydroxide, the concentration of ethanol, the reaction temperature and the reaction time as the variables, DS₁as the experiment index. Using L₁₆(4⁵) orthogonal experiment, we can obtain the optimum conditions were as follows: the chloracetic acid was 0.05mol,the sodium hydroxide was 0.25mol,the concentration of ethanolwas 80%,the temperature of reaction was 35 °C, the time of reaction was 3.0h, the DS₁ of final products were about 0. 922. The past properties of CCMS have been studied, which include the anti-retrogradation characteristics, clarity, the effect of temperature, pH value and rotation rate, the result indicated that the CCMS has not only the properties of single modified starch such as CMS and CS , but also it remedies the shortcoming of single modified starch.