Preparation method of cross-linked hydroxypropyl composite modified starch by one-step process

Abstract

The invention discloses a preparation method of cross-linked hydroxypropyl composite modified starch by a one-step process. The method, considering that both cross-linking and etherification reactions is performed under high temperature and alkaline conditions, synchronously implements the cross-linking and etherification reactions, and comprises the following steps of: adding a swelling inhibitor, a cross-linker and sodium hydroxide into de-ionized water by certain mass percent, stirring and dissolving, adding starch to obtain a starch emulsion, and alkalizing for a certain duration; and increasing temperature, adding a starch etherifying agent of a certain mass percent, neutralizing, washing, centrifuging, hydrating, drying and sieving after the etherification reaction to obtain the cross-linked hydroxypropyl composite modified starch. The preparation method, by synchronously implementing the cross-linking and etherification reactions, shortens independent cross-linking reaction time, prolongs cross-linking reaction time, reduces dosage of a cross-linker, and lowers production cost and energy consumption of products.

Description

technical field [0001] The invention belongs to the technical field of modified starch, and in particular relates to a method for preparing cross-linked hydroxypropyl composite modified starch in one step, which can carry out etherification reaction and cross-linking reaction simultaneously and reduce individual reaction time. Background technique [0002] In the prior art, hydroxypropyl starch is an ether compound formed by introducing hydroxypropyl groups into starch through nucleophilic substitution reaction between propylene oxide and alcoholic hydroxyl groups in starch under alkaline conditions. As one of the representative products of modified starch, hydroxypropyl starch has low gelatinization temperature, high paste transparency, good fluidity, weak retrogradation, high stability, and the paste liquid is less affected by electrolytes, and can be used in a wide range of acid and alkali It has excellent physical and chemical properties such as being used within the pH ...

AI Technical Summary

Problems solved by technology

①, first cross-linking and then etherification reaction: the advantage of this process route is that after the starch is cross-linked, the gelatinization temperature rises, the greater the degree of cross-linking, the higher the gelatinization temperature, which is conducive to the preparation of cross-linking with a higher degree of substitution Hydroxypropyl starch; but the disadvantage is that the concentration of starch milk decreases during the etherification reaction, resulting in a lower efficiency of the subsequent etherification reaction and a longer reaction time

However, the disadvantage is that after the starch is etherified, the gelatinization temperature decreases, and the higher the degree of substitution, the lower the gelatinization temperature, so that in the subsequent crosslinking process of starch, in order to maintain the integrity of the starch granules, more expansion agent needs to be added. Inhibitor, and the pH value required for the crosslinking reaction of starch is far lower than the pH value of the etherification reaction. A large amount of acid needs to be added to adjust the pH value before the crosslinking reaction, which affects the amount of crosslinking agent added and the reaction time is also long